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1. Lund Simula Documentation Using Lund Simula on Unix Systems For Lund Simula version 4 15 or later Lund Software House AB Sweden Lund Simula Documentation Using Lund Simula on Unix Systems Version 4 15 by Boris Magnusson and Per Holm Printed at 7 December 1995 4 13 pm Copyright 1995 Lund Software House AB P O Box 7056 S 220 07 Lund Sweden LSH Lund SIMULA user s manuals Table of Contents 1 Introduction 1 2 An Introductory Example 2 3 Useful scripts 3 4 Compiling 4 4 1 Error Handling 4 4 2 Line Numbers 5 4 3 Compiler Directives 5 4 4 General Description 6 5 Linking7 6 Simula Program Execution 8 7 External Simula classes and procedures 8 7 1 Naming a separately compiled module 8 7 2 Finding attribute files 9 7 3 Interface checking 11 7 4 Maintaining sets of related files with simmake 12 8 Calling external C routines 13 8 1 Simula memory management and C routines 13 8 2 Simple parameters to C routines 14 8 3 Arrays of simple values as parameters 15 8 4 Simple results from C routines 16 8 5 Text parameters to C routines 16 8 6 Text results from C routines 17 8 7 Text arrays as parameters to C routines 17 8 8 C routines as parameters to C routines 18 8 9 C struct as input and output parameters to C routines 18 8 10 C struct as result from a C routine call 19 9 External Library Procedures 19 10 Restrictions and Extensions 20 11 Implementation Notes 21 11 1 Input Output 21 11 2 Simul
2. grams are linked The Run Time System is described in Chapter 6 Appendix C gives some specific hardware information LSH Lund SIMULA user s manuals Chapter 7 gives detailed information on separate compilation of Simula classes and procedures Chapter 8 explains how to call external C procedures 3 Useful scripts You will usually invoke Simula through shell scripts This chapter describes a few useful scripts distributed with the system They are normally to be found in usr local simulabin with links installed to them in usr local bin e simcomp script used to run the Simula compiler and the as assembler when needed to translate the program into an object file see chapter 4 e simld script used to run the ld linker to combine a Simula main program possibly separately compiled Simula classes and procedures and library routines into an executable program see chapter 5 e simmake script used to selectively compile a set of interdependent files as needed see chapter 7 4 e simman script to access the simula on line man pages see chapter 13 These shell scripts take the name of one or more Simula program files as parameters You may give options before the file name An example simcomp h stay simid stay stay p The source program file should have the extension sim By extension we mean the last dot of the file name and any characters following it You need not supply the sim file name e
3. The class MemoryAccess in simlib has operations for the purpose GetI ntAt GetRealAt etc and operations in UncheckedConversion can be useful also in this situation In order to supply the right parameters to these routines one has to know the exact layout of the struct in memory Unfortunately the layout can change with machine version of Unix and C compiler 9 External Library Procedures External library procedures are using a special protocol for calling and parame ter passing The parameter passing mechanism is more general than that for C procedures and can for instance give access to the internal structure of arrays and class objects The use of library procedures therefore demands intimate knowledge of the Simula run time structures and is mainly intended for extended functionality in form of library routines such as those in simlib pro vided by LSH Syntax external library procedure lt call name gt is lt procedure declaration gt Examples external library procedure argv is integer procedure argv external library procedure argc is integer procedure argc external library procedure envp is integer procedure envp These three procedures are included in the Run Time System They give access to the parameters of the command line which invoked the executing Sim 19 LSH Lund SIMULA user s manuals ula program The values returned are exactly the same bit pattern as was passed by the shell to the program a
4. end end The C routine unlink is documented in section 2 of the UNIX manual A sim ilar procedure is included in class FileUtil of simlib 8 6 Text results from C routines C routines that return NULL terminated strings are in Simula specified as text C routine declaration Simula interface specification char text procedure Simula will create a Simula text and copy the contents of the returned NULL terminated string The result returned to the Simula program is thus an ordinary Simula text Potentially this mechanism might leak memory since Simula does not free the returned C string it is not obvious that this should be done in all cases 8 7 Text arrays as parameters to C routines Arrays of strings is a particular data structure expected by some C routines In this case the C convention is to have all the strings NULL terminated and also the array terminated by a NULL element 17 LSH Lund SIMULA user s manuals C routine declaration Simula interface specification char ArrS value ArrS text array ArrS At the call Simula allocates space for the NULL terminated array and all the strings again NULL terminated in C space It is up to the called C routine to free these data structures after use or the call will leak memory In this case call by name is not supported 8 8 C routines as parameters to C routines C routines that require a routine as a parameter can be specified but the actual parameter can
5. ters for use with the rare C compilers that do not follow this convention C procedures needing addresses of locations when called are matched by Simula interface specifications using call by name This is typically used for C routines to return values as a result of the call When called in the Simula pro gram the parameter must thus be matched by an assignable Simula variable C parameter declaration Simula interface specification int 1 name l integer short s Not supported char c see handling of text below float x name x real x double y name y long real y Address are passed as full word 32 bit entries on the C call stack and con version of real to long real does thus not take place in these situations Please notice that call by name expose a Simula internal address which might be valid only during the call since the garbage collector might possibly rearrange Sim ula internal memory as soon as control is returned to Simula C procedures that stores addresses obtained as parameters are inherently unsafe to use from Sim ula and should be avoided or encapsulated within a C routine with a proper interface Also notice that there is in C no syntactic difference between the address of a single value as above and the address of an array of values as dis cussed in 8 3 below In Simula these specifications come out differently 8 3 Arrays of simple values as parameters Simula
6. This means that an imagefile can be treated as any other text file In the case of an outfile the image will be stripped of trailing blanks Printfiles are treated in the same way as outfiles Page skips caused by eject are output as F ormF eed characters A terminal is however treated specially in that FormFeeds are not transmitted To do this would cause inconvenient screen erasures to occur on many video terminals The standard page length linesper page of a printfile is 60 lines A directfile is implemented with fixed record length equal to the image length plus one After each record of a directfile a NewLine is appended which makes it possible to use a directfile as any other text file At the start of execution sysin and sysout are connected to the standard input and output with an image length of 80 characters They may be freely closed and reopened Also note that the image of input and output files are not protected and can be assigned to longer buffers This is particularly convenient for sysin and sysout that is opened by the RTS with80 characters long buffers Input Output and External procedures C routines can be called from Simula and perform 10 on files opened by Simula Beware however that the Simula file image should be emptied before calling C routines because the C routines will work on the UNIX file and buffers and NOT on the Simula image Also C programs should flush buffers before return ing to Simula 11 2 Si
7. again defines a string with directories separated by colons The com piler searches the directory searchlist for these libraries and defines the library searchlist from these names again from left to right This list is finally used to find files searched for The search order for libraries is thus 1 the current directory 2 directories matching the libraries given with the l option from left to right 3 4 With this mechanism it is thus not necessary to supply the full pathname of a file in the source but it can be put together at compile time from three parts the implicit or explicit filename one of the directories given in the library searchlist and one of the directories given in the directory search path The fol lowing examples are equivalent simcomp l usr local simulabin simlib usr local simulabin libsim lt file gt simcomp L usr local simulabin l simlib libsim lt file gt Assuming libsim and simlib are directories installed in the default location usr local simulabin the compiler will look for attribute files and include files in 1 the current directory 2 usr local simulabin simlib 3 usr local simulabin libsim There is furthermore an convenient option to simcomp I which makes simcomp append the list of Simula library directories in usr local simulabin sup plied with the Simula system to the end of directories given with the I option and usr local simul
8. more details on the use of the debugger please refer to the SIM DEB User s Guide 5 An important design goal of the Run Time System and indeed of the entire Simula system has been to keep down the size of executable programs This goal has resulted in the Run Time System being fragmented into several small routines When a program is linked as above you will get only the RTS routines actually referred to by your program LSH Lund SIMULA user s manuals 6 Simula Program Execution This chapter describes how to run your Simula program when it has been com piled and linked To run a program just type the name of the file containing the executable code possibly followed by one or more run time options Example simulaprogram p k 512 In this case p will make the runtime system print a log on message includ ing the current version number and a log off message including time consumed and time spent on garbage collection The k option is used to control the amount of logical memory used by the Simula runtime system For a complete list of all the options see Appendix B To start the program in the Debugger add the d option to the program execution line For more details on how to use the debugger please refer to the SIMDEB User s Guide 5 7 External Simula classes and procedures The Lund Simula system fully implements separate compilation as described in 1 In addition there are facilities for c
9. program will start executing it must occur before all other object code files in the com mand Not all Unix system keep crt0 0 in this location but the file is placed in some other location sometimes named by the person installing the software In such cases the simld script has to be modified to match the local installation This is normally done when Simula is installed If this is a problem at your site it will show as an error message from the linker when using simid The Run Time System is usually found in the library file usr local simulabin lib lipsim ula a To link a Simula program the C library usually in usr libc a must also be available The I options tells the linker to search these two libraries in the correct order Most modern UNIX versions have more advanced linking scheme which means that a more elaborate linking command is needed It is recommended to use the script simld in which these details have been hidden It may be different for different UNIX implementations simld takes the base name of the main pro gram source file as argument you can see an example of this in section 2 If the program refers to separately compiled classes or procedures the names of their source files must also be supplied See an example of such use in section 3 and 7 1 For a detailed decription of simld and options see Appendix A If you want to use the Simula debugger during execution of the program you must add the d option to simld For
10. qua is not in the same prefix chain as the object this is not followed by an allowed class name Bad construction containing qua Wrong qualification around Wrong qualification around else Assign not allowed Standard procedure name not followed by Actual parameter to standard procedure not followed by or Illegal operation on booleans Illegal operation on characters Incompatible types around operator Illegal types around or Objects around or are not in the same prefix chain Not declared Too complicated expression simplify it Bad construction after or There is no attribute called or misplaced Non compatible qualifications of formal and actual parameters Inconsistent number of parameters to formal procedure Inconsistent parameter type to formal procedure Missing index to array Misplaced Simula word Bad actual parameter called by name Bad parameter to formal procedure Missing in procedure call Bad ending of procedure call Missing repetition variable Repetition variable not declared Too many formal or virtual procedures in the current block 33 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178
11. s manuals Too many actual parameters Illegal expression type follows then in conditional expression used instead of Incompatible types in assignment Misplaced if in expression inserted Expression or subexpression starts badly Identifier or literal misplaced probably missing or operator Misplaced if new or this Non arithmetic expression follows or Non ref types in ref assignment Boolean operator operates on non boolean expression Arithmetic boolean or relational operator misused Conditional expression ends badly Conditional expression starts badly Expression before dot is not ref or text There is no text attribute called Non boolean expression follows while Bad parameter list to block prefix No else part in conditional expression Duplicated comma in declaration specification list Too many nested include directives Class not defined Prefix not a class Prefix not defined Too many complicated nested blocks Missing after parameters to class Qualifier not a class Too few indices to array Too many indices to array More than one inner in class body inner not at outermost level of class body ignored Function value not used Non reference expression precedes is in or qua is or in is not followed by a class name Class name after is or in is not in the same prefix chain as the object Qua is not followed by a class name Class name after
12. start of execu tion At the end of execution cpu time as well as the number of garbage col lections is printed input file Connect sysin to file rather than the standard input channel output file Connect sysout to file rather than the standard output channel Note that the input and output of the debugger is not affected by these two options but is still connected to the standard input and output channels These two options make it possible to separate debug I O from program I O This is particularly useful when debugging programs designed to work with piped 1 0 To run a program just type the name of the file containing the executable code possibly followed by one or more run time options Example simulaprogram p k 512 30 LSH Lund SIMULA user s manuals APPENDIX C Hardware specific details This appendix provides some hardware dependent information related to the Lund Simula implementation which is valid for 32 bit computers with represen tation of floating point numbers that match ANSI EII 754 1985 standards Table 2 Sizes in bytes of simple variables on 32 bit computers iten allocated used comment short integer 4 4 2147483648 2147483647 integer 4 4 2147483648 2147483647 real 4 4 3 4E 38 1 1E 38 long real 8 8 1 8E 308 2 3E 308 character 4 1 0 255 acharacter variable is initially assigned the value CHAR 0 boolean 4 1 O false 1 true ref 4
13. supports two ways to specify arrays as parameters to C routines call by name and call by value Multi dimensional array are stored in column major order C routine declaration Simula interface specification int Arrl value Arrl integer array Arrl int Arrl name Arrl integer array Arrl short ArrS not supported float ArrX value ArrX integer array ArrXx float ArrX name ArrX integer array ArrXx double ArrY value ArrY integer array ArrY double ArrY name ArrY integer array ArrY 15 LSH Lund SIMULA user s manuals When call by value is specified Simula makes a copy of the actual array pro vided at runtime allocates space for it in C address space using malloc and pass the address of the copy to the C routine This call method is safe since it does not hand out any address into Simula address space to the C routine but it might be inefficient due to the copying and it might leak memory if the C rou tine does not call free to deallocate the area after use Also if the C routine returns results by filling in the array with values this specification is not mean ingful Arrays of C short are not supported since Simula currently implements both short integer and integer as 32 bit integers see 8 10 for a discussion on how values can be converted When call by name is specified Simula use the address of the first element in the array as the paramete
14. 179 180 181 182 LSH Lund SIMULA user s manuals This class has no parameters Too few parameters to prefixed block Too many parameters to prefixed block Missing or in array expression Illegal character This prefix class has no parameters Conditional statement ends badly If may not follow then in conditional statement Else may not follow for statement Else may not follow while statement Missing then in conditional statement Expression after re activate is not ref process Expression after before after is not ref process re activate in block not prefixed by simulation Expression after at delay is not of type real Too many nested for inspect statements Goto non label This label cannot be reached Actual procedure type not converted Non reference expression follows inspect Identifier after when is not declared when is not followed by class name More than 255 declarations textually in a block The program contains too many blocks Undefined compiler directive ignored Illegal operations on texts Too many visible declarations Syntax error in for statement list Illegal repetition variable Missing or misplaced or in for statement Missing until after step in for statement Variable called by name may not be used as repetition variable Ref array parameter wrong qualification Not a class Missing parameter list to class Real operand in integer division Else may not follow
15. 20 07 Lund Sweden or by email to boris dna I th se Please make sure to include the indicated information on the form next page 36 LSH Lund SIMULA user s manuals Simula error report User identification Reported by Company Phone Telefax email Address System identification Compiler version as printed with p Machine and OS OS version Reason for report _ Compiler error _ Run Time System error _ Debugger error _ Documentation error __ Suggested enhancement Problem description Enclosures if possible a small example program that show the problem Mail to Lund Software H ouse Box 7056 S 220 07 Lund Sweden or boris dna th se For use by Lund Software House Date received Registration no Classification Corrective action 37
16. 3 234 LSH Lund SIMULA user s manuals Limits not specified for array Declarations follow specifications treated as empty body Switch name is not identifier Switch name is not followed by Switch element is not of type label Syntax error in switch element virtual not followed by Name value list follows virtual list Hidden protected list follows virtual list More than one virtual list Virtual already defined Illegal type or kind in virtual specification Cannot assign to text expression Virtual procedure declaration does not match specification virtual in specifications for procedure No match in this class for virtual Incompatible type kind qualification for virtual match Illegal delimiter after inner Virtual proc name is not the same as in specification _ is illegal outside identifiers ISO code is gt 255 Source program line too long Wrong qualification for actual parameter External item is not procedure or class External identification is not text literal External mismatch wrong name type kind qualification Wrong internal format of attribute file for The attribute file is of the wrong version for External module is too old recompile Unknown language in external language procedure External declaration of Simula procedure contains is Too many declarations in the current block Statement instead of expression Prefix declared at wrong block level Constant may n
17. 4 none is represented as zero text 16 16 plus storage for the characters maximum length 65535 31 LSH Lund SIMULA user s manuals APPENDIX D Compiler error messages This listing might be particular useful with compiler option x which makes the compiler report errors as line and error number when found Normally errors are listed and printed with source line and the error text below after the three first passes If the compiler does not complete for example after an unsuc cessful recovery after an error the error messages are never printed In such a situation it might be useful to rerun the compilation with option x The last reported error often gives a hint of the location of the error in the source code In such cases the user is kindly asked to submit a trouble report as of Appendix E no Message text 1 Too many formal procedures in the program 2 _ The program contains too many too long identifiers 3 The program starts badly 4 Rubbish after program end 5 Too few end s extra end inserted 6 Illegal construction before begin 7 Declaration in program text 8 Too deep begin end nesting 9 Integer constant expression out of range 10 Illegal real constant format 11 Integer constant out of range 12 Real constant out of range 13 Real constant expression out of range 14 The program contains too many too long literals 15 Illegal label format 16 This label is already declared as an identifier 17 Multiply defin
18. Data processing Programming languages Simula SS 63 61 14 SIS Box 3295 Stockholm Sweden 1987 ISBN 91 7162 234 9 2 G M Birtwistle O J Dahl B Myhrhaug and K Nygaard Simula begin Petrocelli Charter New York 1975 ISBN 0 88405 340 7 3 R J Pooley An introduction to programming in Simula Blackwall Scientific Publications Great Britain ISBN 0 632 01611 6 ISBN 0 632 01422 9 Pbk 4 P Holm Objektorienterad Programmering i Simula In Swedish Lund Institute of Technology Computer Science Department Box 118 S 22100 Lund Sweden 5 B Kirekrud Object Oriented Programming with Simula Addison Wesley 1989 ISBN 0 201 17574 6 6 S Dahl amp K Lindqvist Objektorienterad programmering och algoritmer i Simula in Swedish Studentlitteratur Lund 1993 ISBN 91 44 37591 3 7 SIM DEB User s Guide Lund Software House AB 25 LSH Lund SIMULA user s manuals APPENDIX A The simcomp simmake and simld commands Syntax simcomp option file The normal action of the Simula compiler is to read the input file and translate it into an object code file and an attribute information file This normal action can be changed by the use of options All produced files have the same name as the input file but with different extensions The object code file is given the extension o The attribute informa tion file is given extension atr This file contains information used by the debugger and for
19. SIMULA user s manuals When using the text method the elements when not characters can be accessed using the routines in BitpackClass in simlib In order the access the right element of the array or the right byte of the text one has to know the exact layout of the C struct in memory Unfortunately the layout can change with machine version of Unix and C compiler Again it is very important to get this kind of interfaces right since the conse quences of errors are severe as any errors in the C language It is therefore highly recommended that interfaces to routines with struct parameters are embedded in Simula procedures or classes that also do some consistency check ing If such classes or procedures are implemented as external Simula classes this tricky interface work needs only to be done once 8 10 C struct as result from a C routine call In most cases C routines are written to return data by filling in a struct sup plied by the caller This is the case we have covered above in section 8 9 where thus the emulated struct is allocated in Simula memory In rare cases C rou tines return results in structures they have allocated themselves They thus end up being allocated in the part of memory managed by C and only returning an address to the struct to the Simula program The C routine can be specified as an integer procedure as described above section 8 4 and the remaining prob lem is to access the fields of the struct
20. The compiler uses the lt compilation time gt which is saved in the attribute file to rebuild the label names If a separate module is recompiled the label names will change If a depending module is not recompiled it will use the old label names This will cause the linker to produce error messages complaining about undefined names The lt name gt part gives a hint on which module to recompile Example example sim contains class Example x integer x main sim contains begin external class Example ref Example P P new Example 2 end The command sequence simcomp example simcomp main simid main example should run with no problem Changing example sim and recompile it but not recompiling main should result in a link time error simcomp example simid main example Undefined example95101309201344001 Recompiling main and then running simld again fixes the problem When recompiling an external module the time stamp is updated only when the signature information in the attribute file is changed This means that recompilation of an external module after minor changes to the statement part can be done without need to recompile the depending modules which might be many since the change ripples through the all the depending modules The compiler issues a warning when it recompiles a module and it needs to update the attribute file There is an option r which makes the compiler terminate the recompilation in ca
21. abin to the end of the string given by the L option A similar option is available with the simld script The above example could thus be written simply simcomp l lt file gt The search list mechanism is also useful to manage locally developed librar ies When handling versions of such libraries it is only necessary to change a name in the I string or the L string in order to switch between library versions Sometimes it can be unclear which attribute file is actually consulted by the compiler This may particularly be the case if several versions of libraries are kept in different directories at the same time In the case there is confusion of where an attribute file is found the f option instructs the compiler to print the full filename of all files it reads 10 LSH Lund SIMULA user s manuals 7 3 Interface checking The compiler is only able to check that the attribute file is up to date in some special cases This is when an external file is read and an external file it is using in its turn is younger If so the compiler will issue a message saying that the intermediate file needs recompilation In general however the check that the source modules have been compiled in the correct order is delayed until link time This check is performed as fol lows The object code for a separately compiled module will contain globally vis ible labels of the form lt name gt lt compilation time gt lt sequence number gt
22. ad the input file and trans late it into an object file and an attribute information file This normal action can be changed by the use of options For a complete list of all the options see Appendix A The compiler runs in six passes and each pass ends with a message All pro duced files have the same name as the input file but with different extensions as described in the previous section The main results are the object code ina file with extension o and the attribute information file with the extension atr This file contains information used by the debugger and for separate com pilation Systems of dependent separately compiled Simula classes or proce dures must be compiled bottom up with independent files first and main programs last See chapter 7 for more details on separate compilation If errors are detected by the compiler they are sorted and listed at the end of the compi lation Errors are by default listed on standard error The input file must be present if not the compiler complains The Simula compiler behaves slightly differently in different UNIX imple mentations In some implementations it produces binary object code directly in a o file In other implementations it produces symbolic assembly code in a s file which is then fed through the assembler This difference is hidden by the simcomp script which invokes the assembler in case the compiler produce assembly code 4 1 Error Handling At t
23. alling procedures written in other pro gramming languages see chapter 8 A source module is contained in one file and may be compiled separately A source module is either a main program a class a procedure several classes and or procedures in the same file When a class or a procedure contained in the file source file is compiled sepa rately an attribute file with name source file atr is created The attribute file contains information about the declaration structure of the module This infor mation is used by the compiler for checking purposes when another module makes use of the class or procedure in source file In addition to information necessary for separate compilation the attribute file contains information which is used by the debugger Therefore an attribute file is created also for a main program 7 1 Naming a separately compiled module It is often practical to put separately compiled classes or procedures in files with the same name as the class or procedure plus the sim extension When a pro grammer is making use of a separately compiled module this is done by declar ing the class or procedurein question as external 1 This is a slight extension or very liberal interpretation of the Standard orig inally a bug which was explored by users and has turned out to be very useful LSH Lund SIMULA user s manuals Example external class Aclass The name of the attribute file can be communicat
24. ation 22 11 3 Garbage Collection 22 12 Managing versions of Lund Simula 23 13 On line documentation and additional libraries 23 APPENDIX A The simcomp simmake and simld commands 26 APPENDIX B Run Time Options 30 APPENDIX C Hardware specific details 31 APPENDIX D Compiler error messages 32 APPENDIX E Error reports 36 LSH Lund SIMULA user s manuals 1 Introduction Simula is a general purpose programming language It is the origin of object ori ented programming The concepts of generalization and specialization is very well supported by the language constructs class and virtual procedure In Sim ula inheritance of actions are just as natural as inheritance of data attributes Constructs for modular programming and implementation of abstract data types make the language well suited for solving complex problems In addition Simula is a well standardized language which means that Simula programs are easy to port from one computer to another A standard application package class simulation turns the language into a powerful tool for process oriented simulation Simula is an extension of Algol 60 and is defined in the Simula Standard 1 Extensions and changes to the language standard are made by the Simula Stan dards Group SSG where the implementors of the language are members Many users are members of the Association of Simula Users ASU The quarterly ASU publication Simula Newsletter is a valuable source of information abo
25. d interpret an intermediate error listing Please report all compiler malfunctions using the error form of Appendix E 4 2 Line Numbers The compiler generates code to keep track of the line number where the pro gram is currently executing This makes it possible to produce informative error messages during run time and to use the debugger facilities Line number code is generated at the first executable statement of each line and at certain other selected places such as at inner and end If you write expressions which range over several source lines the line number will not be updated at the new lines inside the expression This has the consequence that an error that occurs during the calculation of such an expression may lead to a somewhat misleading error message Example 1 begin 2 integer array A 1 10 3 A 1 A 2 4 A 12 5 end The error message will in this case be Subscript out of range at line 3 because that is the line at which the statement started 4 3 Compiler Directives A source program line that has a ASCII 37 as the first character of the line is treated as a compiler directive Note that the only compiler directive which presently is standardized is lt Space gt the line comment The following directives are currently implemented lt white space gt text A directive line with a space or horizontal tab directly following the character is regarded as a comment line LSH Lund SIMULA use
26. directories where it looks for the attribute files The searchlist can be defined in two parts on the command line using the l and L options The I option defines a set of libraries imple mented as directories to search for attribute files The compiler first tries to find these libraries locally or directly if they are absolute filenames if not found the compiler uses the directory searchlist to look for the library directo ries The directory searchlist is defined on the command line with the L option and by the environment variable SIM_LIBRARY_PATH In both cases they define a string with directories separated by colons The compiler searches for libraries first in the directories given by the L option on the command line the directories taken in order from left to right If the needed file is still not found the directories given in SIM_LIBRARY_PATH are searched again from left to right The result of the search is to establish a set of directories matching the library names where to search for attribute files The search order for libraries is thus 1 The mechanism is modelled after the options to Id L and respectively LSH Lund SIMULA user s manuals 1 the current directory 2 directories given explicitly with the L option 3 directories given with the environment variable SIM_LIBRARY_PATH The library searchlist is defined on the command line with the I option which
27. dure lt Identifier gt String is lt procedure declaration gt The purpose of the lt procedure declaration gt is to describe the procedure and its parameters to the compiler The declaration must have an empty procedure body written as or begin end Examples external C procedure put is procedure put x integer x external C procedure get is integer procedure get begin end external C procedure xxx XDisplay is integer procedure InitDisplay The name of the C procedure to call can be given in two different forms as shown above In the first alternative lt dentifier gt is converted into lower case in the second case q dentifier gt is ignored and String is used exactly as given with regards to upper lower case In the object code this name is used to iden tify the C procedure and in both cases prefixed with an underscore on Unix BSD implementations to match C compiler conventions The name given in the lt procedure declaration gt is used in the Simula program to call the C procedure and can thus be used to rename it The Simula standard describes an alternative syntax for the declaration of non Simula procedures without the is lt procedure declaration gt clause This possibility is not supported 8 1 Simula memory management and C routines Simula data structures i e objects procedure activation records arrays and texts are allocated in a separate memory area This memory area is mana
28. ed by Id to directories where the corresponding object libraries are kept The simman command Syntax simman lt option gt filename simman is an interface to the man utility It searches for man pages in usr local simulabin man only which makes it easy to install and update Simula 28 LSH Lund SIMULA user s manuals related man pages Possible options given to simman are passed on to man See man man for their meaning Environment variable SIMULAHOME The environment variable SiIMULAHOME is understod by all the script When not defined it is defaulted to usr local simulabin When SIMULAHOME is defined to something else the above scripts will interpret that as defining a directory where Simula is installed This can be used to manage different ver sions of Lund Simula for example checking out a new version before made pub lically available or for single user systems installed in a private directory 29 LSH Lund SIMULA user s manuals APPENDIX B Run Time Options Syntax program option Options d Start execution in the Simula debugger SIMDEB only possible if the pro gram has been linked with the SIMDEB library see 7 g Print a message each time the garbage collector is called k n Set the memory pool size used for dynamic allocation to n Kbytes m n Set the memory pool size used for dynamic allocation to n Mbytes p Print a message indicating the size of the storage pool at the
29. ed label 18 Formal parameter already defined 19 20 Illegal construction 21 Parameter transmission mode already defined 22 Specification of non existent formal parameter 23 More than one name or value list 24 Too many nested inspect statements 25 short not followed by integer accepted as short integer 26 long not followed by real accepted as long real 27 28 Proc switch label cannot be formal parameter to class 29 Value is illegal mode for proc switch label parameter 30 Missing specification of formal parameter 31 Multiple declaration 32 Missing do in for statement 33 The program contains too many virtual quantities 34 Missing right parenthesis inserted 35 Too many right parentheses 36 The declaration specification list contains a non identifier 37 Missing comma in declaration specification list 38 Too many nested blocks 39 Too many errors stopped the compilation 40 Too many virtual declarations in class 41 Non numeric value as array index 42 Inconsistent number of parameters to formal array 43 Formal parameter already specified 44 Name is illegal mode for formal parameter to class 45 Misplaced name value list accepted 46 Misplaced operator in expression 47 _Non boolean expression follows if 48 Incompatible expressions around else 49 Incompatible types of formal and actual parameters 50 Too few actual parameters 32 107 108 111 112 113 114 115 116 LSH Lund SIMULA user
30. ed to the compiler in one of two ways either implicitly or explicitly In the above example implicit naming is used The attribute file is then supposed to have the name aclass atr In general the attribute file is supposed to have the name external id atr where the file name external id atr is always lower case regardless of the actual spelling of the class or procedure name in the program text Implicit naming is often convenient to use but when this is not the case the attribute file can be named explicitly Example external class Aclass Attribute File Here the compiler assumes that the attribute file is named Attribute File If no such file exists the compiler will automatically supply an atr extension to the file name and try Attribute File atr instead When using the extended capability of putting several classes or procedures in the same file the external declara tion should match the first declaration in the file The rest of the declarations in the file are brought in as a side effect of bringing in this first declaration 7 2 Finding attribute files When a source module is compiled all the attribute files named implicitly or explicitly by external declarations must be available and contain up to date information The compiler always look in the current working directory first for attribute files and include files it needs If the file is not found there the com piler uses the library searchlist a list of
31. erred directly from the Simula image to the terminal In other words terminal files output everything there is to output at once Beware that a UNIX system behaves as follows when reading from a termi nal in cooked mode see tty 4 and read 3 in the UNIX manual e At most one line terminated by the user typing a carriage return is transferred e At least one character is transferred i e a program will hang until a car riage return is typed This implementation assumes that only infiles and outfiles are used as ter minals l e a terminal is never opened as a bytefile nor as a directfile Table 1 shows which files use which kind of buffering file Large buffer line buffered unbuffered infile X X outfile X X directfile X inbytefile X X outbytefile directbytefile X Table 1 Buffering technique used for Simula files 21 LSH Lund SIMULA user s manuals All legality checks legal file name etc are performed by the operating sys tem Note that a file object is created without any of these checks the object is not connected to a UNIX file until the call to open All normal text files can be read from a Simula program When reading from an imagefile the NewLine character which terminates a line is not transferred to the Simula image When writing to an imagefile each call of outimage will result in the current image contents being output with a NewLine appended as terminator
32. ged by a garbage collector which means that data structures can be moved in mem ory in which case it updates all references kept in the Simula memory area accordingly Addresses into the Simula memory area which have been created and used when calling a C routine can naturally not be found or updated by the Simula garbage collector Such addresses are therefore very short lived and risk to be invalidated when the garbage collector gets control the next time They are only guaranteed to be valid for the duration of the call where created and should thus not be stored or copied in the called C routine C routines that violate this rule are inherently unsafe and should be avoided or encapsulated within a C routine with a proper interface In a couple of situations addresses to Simula data structures must be to exposed to C routines Calling C routines that have text strings arrays or C 13 LSH Lund SIMULA user s manuals structs as input parameters is one situation Here the C routine only accesses data in the Simula memory area If the Simula interface specification or the call is erroneous or does not meet the expectations of the C routine Say a text string is shorter than expected this means that the C routine will fail or calcu late bad results but it will not likely harm Simula data structures A more com plex situation is created by C routines expecting output parameters in the form of simple variables strings arrays or C str
33. he end of the fourth pass error messages are written to the standard error file usually the terminal The compiler is designed to recover from an error and to detect all errors in a program Even if a program contains a number of errors code is usually produced When an error is found a call to a special run time error routine is inserted in the produced code This makes it possible to execute and debug a program even if it does not compile correctly The following error types are defined Warning does not affect the produced code in any way Error due to a violation of the Simula rules Code is produced to call a run time routine which issues an error message LSH Lund SIMULA user s manuals Fatal aborts the compilation immediately no code is produced OS due to violation of some operating system rule eg illegal file name Internal probably due to compiler malfunction Often an internal error will have its root in a user error so ingenious that the compiler construc tors have never thought of it If the compiler reports Warnings and or Errors the resulting program is exe cutable if however any of the other error types are reported these have to be corrected and the program recompiled before the program can be executed Error codes and error messages are listed in appendix D If for some reason the compilation is terminated before the error listing is produced consult Appendix D for instructions on how to obtain an
34. if Simula is given a large pool to work in as long as it can be kept in main memory on the computer used Unfortunately also the time to per form one collection goes up with memory size For interactive programs it can therefore be of interest to give a Simula program a smaller pool to work in to achieve shorter collection pauses although more frequent As rule of thumb 10 15 of the overall time consumed by the garbage collection or leaving 1 3 to 1 2 of memory free after each collection are usually reasonable compromises 12 Managing versions of Lund Simula With version 4 15 of Lund Simula all the scripts mentioned in this manual sim comp simld simmake simman are dependent on the environment variable SIMULAHOME The value of this variable controls where these scripts look for Simula related files If not defined the value usr local simulabin is used as default this is the default installation directory for Lund Simula SIMULAHOME affect the selection of compiler to run versions of runtime system and other libraries distributed with Lund Simula and other processors such as simmake It might be meaningful to define SIMULAHOME to the directory where a new version of Lund Simula is installed in order to check it out before making it publicly available SIMULAHOME can also be convenient to use on machines where Simula for some reason have not been installed in the default location 13 On line documentation and additional librarie
35. iles and can do a better job than make when recompiling files after a change In the simplest case a set of Simula files in a directory can be recompiled with the single commana simmake sim c It is however often a good idea to put this command and the command to build an object library into a simple Makefile FILES filea sim fileb sim filec sim LIB libuseful a USEDLIBS L usr local simulabin l simlib libsim TODO COMPILE LIB COMPILE simmake USEDLIBS FILES c LIB FILES sim o ar c LIB FILES sim o In this example you need to update the macros FILES and LIB to reflect the contents and name of your own library and USEDLIBS to reflect dependencies on separately compiled classes procedures in other Simula libraries Simmake takes the same L I and I options as described above for simcomp Simmake can also be used more conservatively It can print the commands needed to update a set of files rather than executing them option s or auto matically create the dependency part of a Makefile option m Details of sim make and its options are found in Appendix A 12 LSH Lund SIMULA user s manuals 8 Calling external C routines Routines written in C may be called from a Simula program The C routines must be declared in the Simula program according to one of the following two forms external C procedure lt Identifier gt is lt procedure declaration gt external C proce
36. inspect statement Stand alone class name probably missing new new is not followed by an identifier when is not followed by an identifier String not closed at end of line inserted Character constant not closed inserted Name parameter wrong qualification Illegal directive parameter Missing directive parameter and in the same statement A statement starts badly Wrong kind of actual parameter to procedure Ref procedure parameter wrong qualification Dot notation not allowed for object with class attributes Statement ends badly probably missing Cannot reach class declaration via dot notation Procedure class name is not identifier Procedure class name is not followed by or Missing after formal parameter list in declaration of Transmission mode specification of non existent formal parameter Missing do or when in inspect statement Short real is treated as real Long integer is treated as integer Missing in ref declaration specification Qualification in ref declaration is not identifier Missing in ref declaration Declaration specification list does not start with identifier Missing semicolon Erroneous array limit specifications 34 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 23
37. l below In sum mary the parameter specification name means that a Simula internal address is transferred to the C routine This might cause consistency problems for the Simula runtime system if the address is saved by the C routine over garbage collection or if it does not match what the C routine expects The specification value means that a memory area is allocated i C memory space by calling mal loc This might cause memory leak problems if the called C routine does not call free in order to de allocate the data array or string 8 2 Simple parameters to C routines Simple parameters can be transmitted to a C routine using call by value or call by name matching C declarations of the form int and int respectively 14 LSH Lund SIMULA user s manuals C parameter declaration Simula interface specification int l short s short b integer integer s Boolean b char c character c float x long real x double y long real y float x real x rarely see below By C conventions parameters are passed on the C call stack Integer values are expanded to full word 32 bit quantities for alignment They should thus always be specified as integer or boolean when applicable Similarly floating point numbers are by most C compilers converted to double long real when passed as parameters Lund Simula also support specification of real parame
38. mpiled Simula procedures or classes where the location of the corresponding 0 files are given explicitly Libraries are names of binary libraries of translated Simula or C code to search for matching routines Note that ld searches these libraries one by one left to right so the relative order between libraries that depend on each other are important Libraries can be explicitly named or given with the I lt dibrary gt options as of below Note that the option L lt path gt in such cases becomes impor tant since it defines the directories of where to search for libraries Options d include debugger support with the executable lt ibrary gt include the file lib lt file gt a for search for object code to include L lt directory gt include lt directory gt for search for libraries a files I include a search of the libraries installed with the Lund Simula system Shorthand for L usr local simulabin lib Isimlib Ilibsim etc Notice that options for simld matches these for simcomp and simmake Spec ifying L dirl dir2 should be matched with Ldir1 Ldir2 to simid and specify ing l Siba libb should be matched with lliba llibb All three scripts takes the short hand option I for including all libraries installed with the Lund Simula system Also definition of the environment SIM_LIBRARY_PATH interpreted by the simcomp command can be matched with a definition of LD_LIBRARY_PATH interpret
39. mula program with the help of your favorite text edi tor Give your program the name stay sim begin Outtext Simula is here to stay Outimage end The program is compiled with the simcomp command simcomp stay Lund Software STANDARD Simula Compiler revision 4 15 Executing at Lund Software House 12 OCT 95 17 16 00 End of pass 1 0 090 seconds End of pass 2 0 090 seconds End of pass 3 0 160 seconds End of pass 4 0 020 seconds End of pass 5 0 000 seconds End of pass 6 0 280 seconds No errors and no warnings End of Simula compilation The simcomp command will produce two files stay o and stay atr The file stay o contains the relocatable object code The stay atr file contains information for the debugger and for separate compilation it is of no concern here The pro gram is linked with the simld command simid stay The simid command will produce the file stay containing executable code You can now run the program by entering stay Simula is here to stay You will ordinarily use Simula through shell scripts simcomp simmake and simld Use man simula or simman simula for on line documentation The next chapter describes a few useful scripts distributed with the system The compiler itself is described in chapter 4 and appendix A gives the complete syntax and semantics for the command which invokes the compiler Compiler error messages are listed in appendix D Chapter 5 describes how Simula pro
40. mulation The sequencing set of the system class simulation is implemented as a singly linked list No separate event notices are generated all sequencing information is kept in the process objects themselves The event time attribute of a process object is a long real quantity 11 3 Garbage Collection The algorithm for memory allocation is designed to avoid creating garbage Often a block instance can be removed from the run time stack when it is left Data objects such as texts and arrays cannot be removed neither can class instances Due to these circumstances normal Algol blocks and objects of this type are separated in memory Blocks dynamically enclosed by a class object are allocated among the data objects but are also removed when they are left if possible 22 LSH Lund SIMULA user s manuals The time for a garbage collection is highly dependent on the structure of the program and even more on the amount of data which has to be moved by the garbage collector The runtime option p can be used to see how much of overall execution time is consumed by the garbage collector With runtime option g amessage are printed after each garbage collection giving the consumed time and the amount of free memory available after the collection Memory utiliza tion can be tuned by giving the Simula program more or less memory pool to work in using the options k or m In general the fraction of the overall time goes down
41. nted at the end of the compilation z Symbolic intermediate code Produce symbolic intermediate code on the file with extension zr This option is mainly intended for implementor use The simula compiler Syntax simula option program Options The same options as for simula with the following additions p Print messages The compiler will print a short message after each pass default for simcomp S Symbolic assembly code Produce symbolic assembly code on the file with extension s n No object code Produce no relocatable object code Normally object code is produced on the file with extension o Default for compilers that can not produce object code The simmake command Simmake reads Simula source files and analyzes the dependencies between Simula files by looking for external declarations and include directives This information can be used create a Makefile or as an alterative simmake can run simcomp to recompile all files affected by a change Simmake understands the information in the attribute files and can do a better job than make when recompiling files after a change since make is only looking at file systems time stamps The possibility to create a makefile is usefull also to get an overview of dependencies in a system of separately compiled Simula classes and procedures Syntax simmake option program Options c Compile the programs which need compilation by calling simcomp c lt
42. of the compiler a few other limitations exist but will probably never be exceeded Number of array subscripts 15 Length of prefix chain 16 Number of declarations in one block 32767 Max significant characters in an identifier 80 20 LSH Lund SIMULA user s manuals 11 Implementation Notes 11 1 Input Output This section describes aspects specific to LUND Simula under UNIX Unix streams files with buffering are used to implement Simula 10 The implementation of files are compatible with the UNIX Standard 10 library sec tion 3S routines but do not actually call upon any of the section 3 routines for reasons of efficiency and correctness All random access files are unbuffered in the sense that they have no buffer of their own seen from UNIX s viewpoint I e there is no buffer associated with the FILE data structure of section 3S Standard IO Instead the Simula image is used by directfiles All other files have a large buffer which is allocated by the RTS This buffer is used for efficiency reasons its size is BUFSIZ as defined by lt stdio h gt a com mon size is 4K bytes Thus large chunks can be moved to and from disk at a time All terminal 10 is line buffered Files connected toa terminal havea buffer of their own in UNIX Standard 10 just like other buffered files This buffer is however used by Simula files only when reading and then it contains at most one line at a time When writing the bytes are transf
43. only be another C routine The parameter must be specified call by name C routine declaration Simula interface specification Cfunc name Cfunc lt type gt procedure Cfunc Example external C procedure foo is long real procedure foo x y long real z y external C procedure Integrate is long real procedure Integrate a b step f name f a C function must be used at call long real a b step long real procedure f Use long real Result Result Integrate 1 10 0 001 foo 8 9 C struct as input and output parameters to C routines Many C routines expect an address of a C struct as one of its parameters A struct is an area of memory with a specified layout Such a structure can be emulated in Simula by using an integer array of the proper size or a text Depending on the layout of the actual C struct one or the other might be more convenient to use We are not using Simula class objects for this purpose since the mapping from the declaration of a class to the actual memory layout is non trivial C routine declaration Simula interface specification reci Struct1 name rec1 integer array rect rec2 Struct2 name rec2 text rec2 When using an array integer elements of the struct can be accessed as nor mal Elements of other types in the struct character 16 bit short real long real can be mapped to integer by the routines such as ItoSS ItoR IItoL in class UnsafeConversion in simlib 18 LSH Lund
44. ot be of type ref This constant is not yet evaluated Constant definition contains non constant element Protected specification of undefined attribute Protected but virtual specification not in same class Attribute is already specified as hidden protected Too many hidden protected specifications Hidden specification of undefined attribute Hidden specification of non protected attribute Negative value raised to real value Zero value raised to non positive value is must be followed by procedure specification is lt procedure declaration gt procedure body must be empty Non Simula procedure cannot be actual parameter Non Simula procedure cannot be virtual match Function call in parameter to external non Simula procedure 35 LSH Lund SIMULA user s manuals APPENDIX E Error reports We will be very grateful if you report all compiler or Run Time System malfunc tions to us Also please report any suggestions regarding enhancements of the Simula system or related documentation When submitting an error report please follow these guidelines e Usethe standard error report form see the next page e Describe the problem as exhaustively as you can e Whenever possible enclose a program listing and any other relevant list ings e Try to isolate the problem Avoid submitting a 1000 lines program with the message Does not work Error reports should be mailed to Lund Software House POBox 7056 S 2
45. r s manuals Yd NCLUDE filename The source file with the name filename is included in place of the INCLUDE directive line INCLUDE directives may be nested i e the included file may contain another INCLUDE directive but only to a level of 5 YLINENUMBERS OFF Inhibit generation of code to keep track of the source program line numbers dur ing run time This will lead to reductions in code size and execution time for the affected program sections but will also make the use of several of the debugger commands impossible See also h option to simcomp Appendix A YLINENUMBERS ON Turn on the generation of line number code This is the default This option is ignored if the h option is set upon invocation of the compiler PAGE Eject to the top of a new page in the listing file If no program listing is being produced this directive has no effect YLIST OFF Turn off listing of the following lines of the source program until a LIST ON command is encountered YLIST ON Turn on source program listing This is the default It has effect only if the option is set upon invocation of the compiler TITLE text Print a heading on each page of the program listing The heading text is sepa rated from the directive TITLE by one space character PAGELENGTH n Set lines per page to n for the program listing n must be a positive number The default value is 60 4 4 General Description For the interested reader the six passes of
46. r to the C routine When using this mode please observe that the address is only valid during the call and make sure that the length of the provided array is what the C routine expects so it will not distort the Simula internal data that happens to be allocated after the array 8 4 Simple results from C routines Simple function results are specified as returned as integer real or long real C routine declaration Simula interface specification int integer procedure short integer procedure or boolean procedure char character procedure float real procedure double long real procedure C functions that return addresses of C structures can be specified in Simula as integer procedure The Simula program can store such addresses and use them as parameters to future C routine calls but it can not access the C data structures directly see section 8 9 for how this can be done through a set of library functions 8 5 Text parameters to C routines Strings in C are often stored using the convention with a NULL character as end marker Simula provides two alternatives for specifying how a Simula text should be transferred toa C call call by value and call by name C routine declaration Simula interface specification char S value S text S copies to C sting char S name text S uses Simula text Specifying the parameter as call by value means that Simula allocates a string in C address space copies the actual parameter e
47. rgv argc and envp are documented in the UNIX manual see for instance execl in section 3 The external class CmdLi neClass in simlib give more convenient access to the command line using the Simula style of command line switches As an alternative UnixCmdLineClass gives unrestricted access to the command line and also environment variables See documentation of the library Simlib for details 10 Restrictions and Extensions This chapter briefly describes the restrictions and extensions that apply to all LUND Simula implementations Implementation Extensions The following language extensions may cause problems when moving a Simula program to another computer e Calling procedures written in other programming languages e Thecompiler directive INCLUDE e Accepting several classes in the same file Implementation Restrictions The following restrictions apply e A class must be defined textually before all its subclasses e System defined procedures may not be transmitted as parameters e Bytesize 1 sect 10 8 A bytesize of 8 is always returned e Locking and unlocking of files is not supported under Unix The following Simula feature is ignored e Thesetaccess option APPEND 1 sect 10 1 1 is just ignored if present In UNIX APPEND means that all output goes to the end of the file which is not what we want for Directfiles Compiler Capacity Limitations The following table gives a list of the most important capacity limitations
48. s This document as well as the SIMDEB User s Guide are found in usr local simulabin in postscript form and can be printed as needed simman is used to access on line man pages simman simula gives an overview and pointers to other man pages simman simcomp simmake simld give details for each script simlib Simlib contains a set of classes with operation that are hard to write directly in Simula One group of classes contain functionality on the bit level Here are operations to manipulate bits of integers change type of a bit pattern and access memory locations directly given the memory address Another group of classes interface to Unix facilities that are frequently used Here are routines to read directories find out the status of a file and to parse the command line A users manual is stored in usr local simulabin simlib in postscript form 23 LSH Lund SIMULA user s manuals simman simlib lists the classes in the library with a one line description simman lt classname gt provide interface descriptions for classes and their operations in the library Notice that names are spelled with all lower case char acters to avoid confusion libsim On line documentation for libsim follows the pattern for simlib with a postscript manual and man pages available through simman This library contains a set of convenient procedures that are written in Simula The procedures fall into several groups e Te
49. script gt Compile programs needing compilation by using lt script gt s Print the commands to compile the programs which need compilation using a pessimistic assumption that all compiles result in updated attribute files S lt Script gt same as s but use lt script gt rather than simcomp for compilation m Produce a Makefile to recompile programs using simcomp m lt script gt same as m but use lt script gt rather than simcomp L lt dirl gt lt dir2 gt directory searchlist with same meaning as for simcomp simmake also interprets the environment variable SIM_LIBRARY_PATH in the same as simcomp does lt dJibl gt lt dib2 gt library search list with the same meaning as for simcomp 27 LSH Lund SIMULA user s manuals C lt Jib3 gt lt ib4 gt library search list searched before the I list Simula files found using this path that needs compilation are compiled while files found using the I list that are assumed to be compiled up to date I include a search of the libraries installed with the Lund Simula system Shorthand for L usr local simulabin I simlib libsim The simld command Syntax simld main lt option gt lt separatemodules gt lt libraries gt simld is an interface script to the linker Id Options not recognized by simld are passed on told The name of the Simula main program must appear first Separatemodules are separately co
50. se it needs to update the attribute file This option might 11 LSH Lund SIMULA user s manuals be useful when doing changes to modules that are used by a large volume of software or by many users In such cases it might be desirable to coordinate changes that require re compilation 7 4 Maintaining sets of related files with simmake It is recommended that Simula external classes and procedures are kept in a directory with a name that reflects the library functionality The standard Unix way of maintaining the compilation consistency of a set of files is to use the make facility In order to use make the dependencies among related files are col lected in a file a Makefile make will automatically order necessary recompila tions depending on the modification dates on the involved files Lund Simula offers the simmake utility to manage this task Simmake reads Simula source files and analyzes the dependencies between Simula files by looking for external declarations and include directives This information can be used create a Makefile automatically This works well but there are some slight drawbacks the Makefile needs to be updated when the dependencies change Also since make is looking at time stamps it will recompile files unnec essarily when a recompilation has resulted in an unchanged interface As an alternative simmake can be instructed to run the compiler directly Simmake understands the information in the attribute f
51. separate compilation If errors are detected they are listed at the end of the compilation Errors are by default listed on standard error The filename can be givien with or without the extension sim It must be present Compiler Options L lt dirl dir2 gt Colon separated list of directories of where to search for libraries specified by the I option Search order is dir1 dir2 etc SIM_LIBRARY_PATH lt dir3 dir4 gt The content of this environment variable is concatenated to the content of the L option Useful for a default path to be used in a series of compilations lt Jib1 lib2 gt Colon separated list of libraries of where to search for Simula attribute files and include files The full pathname of the libraries are iden tified by searching the directory searchlist defined by the L option and the SIM_LIBRARY_PATH environment variable The result is the library searchpath with one element for each item in the I parameter lt dirn gt lt libl gt lt dirn gt lt ib2 gt I Include a search of the libraries installed with the Lund Simula system Shorthand for L usr local simulabin I simlib libsim f Report all files read during compilation Useful to sort out binding of depen dencies on external files r Specifies recompilation the compilation is aborted if the interface part of the attribute file would need to be changed h Line numbers inhibited Do not produce code
52. tation for simsocket follows the pattern for simlib with a postscript manual and man pages available through simman simxlib This is library of interface routines to the popular X11 windowing system The many operations has been grouped into classes representing abstractions and concepts found meaningful to understand the system There is almost a one to one relation between operations on the xlib level and in our interface Simxlib is designed to work together with the simioprocess library This library is not yet complete and the documentation is to a large extent missing For the details we refer to X11 documentation Often the classes in this library match chapters in tutorials on X programming For a person with some experience in X program ming we hope however it to be possible to figure out how to use this library at least for simple cases There is a very preliminary and not completed postscript 24 LSH Lund SIMULA user s manuals manual provided The library and the documentation will be improved in future releases Other libraries There may be more libraries distributed with Lund Simula not mentioned in this short overview Use the simman simula on line help to find out about which additional libraries that are also installed Each library follows the same pat tern as described for simlib or if some of the documentation is missing will be provided in a future release References 1 Simula Standard
53. the compiler are briefly described Pass1_ This pass performs the lexical analysis Pass 2 Declarations and block structure are analyzed The program is divided into blocks A block is the input unit to pass 3 Pass 3 Syntax and semantic analysis is done and intermediate code is pro duced The intermediate code can be regarded as machine code for a fictitious computer with instructions on a slightly higher level than that of the target computer Pass 4 This pass produces a sorted list of the source code with line num bers and error messages if errors are present It also writes a list of the encountered errors to the standard error file usually the termi LSH Lund SIMULA user s manuals nal Most of the actions of this pass are optional and governed by options Pass5 Prints the intermediate code in symbolic form if requested by the z option This facility is mainly for use by the compiler implementors Pass6 Translates the intermediate code to machine code 5 Linking A compiled Simula program must be linked with Simula s Run Time System The linking is done by the standard UNIX linker Id The linker resolves all ref erences from your program to the Run Time System The following simplified linker command is usually given ld o program lib crt0 o program o simula lc This gives as output executable machine code on the file program as specified by the o option The file lib crt0 o contains the entry point where the
54. to take care of line numbers during run time This option should be used only in fully tested programs since it makes use of several of the debugger commands impossible The benefits resulting from use of the h option are savings in object code size and in execution time list Listing Produce a list file with the same name as the input file but with extension lis It contains the source program text line numbers and error messages file lis will be produced even if the compiler was stopped by a fatal error e Error listing Produce an error list on file with extension err This is really the same as redirecting standard error The error list normally appearing on the terminal is written to the file with extension err instead x Direct error messages Error messages will be written on the console as soon as the errors are detected The message will give less information than that at the end of pass five This option is mainly intended for implementor 26 LSH Lund SIMULA user s manuals use but can be useful if the compiler for some reason can not complete See Appendix D for matching error numbers with error messages w Warning messages inhibited Normally at most 64 warnings and errors will be produced then the compilation is aborted With the w option all warn ings will be inhibited and not counted in the sum of errors and warnings Even when warning messages are inhibited the number of warnings will be pri
55. ucts In this case the C routine is actually storing values in the Simula memory area If the Simula interface or the call itself is erroneous Say a text buffer or an array is shorter than expected this might result in the C routine overwriting essential information in the Simula memory area As a consequence the Simula program might fail but often much later possibly during the next garbage collection This is a situa tion well known to C programmers but this is not supposed to happen in Simula without calls to C routines External C routines must be called with simple parameters not involving function calls or expressions This restriction is introduced in order to not risk a garbage collection being triggered while parameters are calculated It is recommended that interface specifications to C routines are written and tested with extra care since this is information that the Simula compiler can not check and has to trust It is often also a good idea to encapsulate the C routine call within a Simula procedure that checks the validity of actual parameters and maybe also provides a slightly nicer and more intuitive interface to the C routine Example see 8 5 for details on text parameters procedure XXX T text T begin external C procedure XXX is procedure C_XXX T L name T text T integer L if T notext then begin C_XXX T T lenght end end XXX In the C routine interface specifications given in more detai
56. ut mat ters concerning Simula This document is a guide on how to use the Lund Simula system it is not a guide to Simula itself It is written with the assumption that the reader has a fair knowledge of Simula For an introduction tothe language Simula begin 2 An introduction to programming in Simula 3 and Objektorienterad Program mering i Simula 4 in Swedish Object Oriented Programming with Simula 5 and Serafim 6 are recommended Throughout the document RTS is used as an abbreviation for Run Time Sys tem In the examples the font helvetica is used for computer written text and helvetica italics for text typed by the user is the UNIX command prompt The Simula system for UNIX has been developed by Lund Software House Sweden It is a sub implementation based on the Simula system devel oped by Lund Software Sweden It conforms to the Simula Standard The sys tem features a powerful symbolic debugger SIMDEB SIMDEB is documented in a Manual of its own 7 Addresses Lund Software House P O Box 7056 S 220 07 Lund Sweden ASU Secretary Henry Islo The Royal Institute of Technology Department of Manufacturing Systems S 100 44 Stockholm Sweden 1 UNIX is a trademark of AT amp T LSH Lund SIMULA user s manuals 2 An Introductory Example Before diving into the details of the system we show an example of a Simula program and how to compile and run it at your installation Create the following Si
57. xt utilities such as Front Rest FrontStrip Search e Edit deedit utilities such as CheckReal GetRadix PutlntAtPos and rou tines for scanning Simula text e Some mathematical and statistical utilities e Routines for sorting and searching Utilities for dealing with Swedish national characters iba was first developed at QZ Stockholm for the DEC 10 Simula imple mentation The parts of libsim that are available here are those that were porta ble Parts that have been removed are procedures that has been accepted as part of the standard Simula library or were closely dependent on the DEC envi ronment and might be done differently in a Unix implementation simioprocess This library contains a set of classes implementing a process concept useful when dealing with external events These are seen as files in Unix such as stdin connections to other programs such the X11 window manager or Clients and Servers This library makes it possible to write Simula processes that work in response to events arriving from such files On line documentation for simio process follows the pattern for simlib with a postscript manual and man pages available through simman simsocket This library contains classes that makes it simple to write Client Server appli cations in Simula communicating over Unix sockets on TCP IP possibly execut ing on different machines The classes work well together with the simioprocess library On line documen
58. xtends it with a NULL character and uses the result as the parameter to the C routine It is thus safe in that it gives the C routine a C string to work with It is assumed that the called C routine will free the string when no longer used if not it will leak 16 LSH Lund SIMULA user s manuals memory This mechanism also means that any changes or results left in the string by the called routine are lost Specifying the parameter as call by name means that Simula simply will use the address of the first byte of the text string in the Simula address space as parameter to the C routine In this case the Simula caller of the routine must make sure that the supplied parameter is properly NULL terminated In this case there is no risk for memory leaks but the called C routine should not save the supplied address longer than the duration of the call There is as always a risk that the called C routine might make severe damage to the Simula data structures in cases such as not proper NULL termination of the string or if it is not of the length expected by the C routine Example of typical usage of external C routine with a text parameter begin external C procedure unlink is integer procedure Delete_file File_name name File_name text File_name text Filename Outtext File to delete Breakoutimage Inimage Filename Sysin Image Strip amp 0 if Delete_file Filename lt gt 0 then begin Outtext failed Outimage
59. xtension if not the compiler will extend the sup plied name with this default extension Various files are produced when running the scripts The names of these files are made up from the base name of the source program file and an appropriate extension e any sim extension is stripped from the source file name before the name of a produced file is made up Using the above example let us show the names of the files involved stay sim Simula source program stay atr attribute information stay o object code stay executable machine code stay s optional symbolic assembly code stay lis optional list file stay err optional error message file stay zr optional symbolic intermediate code A program may consist of separately compiled classes and procedures in addition to the main program These has to be compiled bottom up in the order they import each other When linking such a program the names of the sepa rately compiled components must also be supplied The same goes when a Sim LSH Lund SIMULA user s manuals ula program calls routines written in other languages Then the names of the files containing the object code for these routines must be supplied to the linker An example simld myProg classA procedureP Croutine IX 4 Compiling The command which invokes the Simula compiler has the following general structure simcomp option file The normal action of the Simula compiler is to re

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