DBPL Memo 121-91 VAX Modula-2 User's Guide VAX DBPL User's
Contents
1. file spec You may specify a file for the object module The default is a file of type OBJ which takes the name of the source file If the source file contains a definition module this qualifier has no effect By default OBJECT is enabled for main and implementation modules disabled otherwise QUERY The QUERY qualifier forces the compiler to ask explicitly for the symbol files to be read By default QUERY is disabled and the compiler uses a standard strategy to search for the symbol files see section The standard search strategy is also effective when QUERY is enabled but no file specification is given SYMFILE A symbol file is created if the source contains a definition module It has the form SYMFILE tile spec You may supply an optional file specification for the symbol file The default is a file of type SYM with the name of the source file By default SYMFILE is enabled for definition modules disabled otherwise Summary DBPL Command Qualifiers Qualifier Negative Form Default CHECK NOCHECK CHECK CREATE NOCREATE NOCREATE CROSS_REFERENCE NOCROSS_REFERENCE NOCROSS REFERENCE DBPL NODBPL DBPL DEBUG NODEBUG NODEBUG LIst file spec NOLIST NOLIST interact LIST batch LOG NOLOG NOLOG interactive LOG batch MACHINE_CODE NOMACHINE_CODE NOMACHINE_CODE opJEct file spec NOOBJECT OBJECT QUERY NOQUERY NOQUERY SYMFILE file spec NOSYMF ILE SYMFILE 2 22. omit the debug qualifier in the link command Now you can start the application with run gdemo run gdemo2 If you have used the debug version you should type go after the debugger prompt or start your application simply with run nodebug gdemo This avoids the activation of the debugger too You can use the module management facilites MMS of the VAX operating system to keep track of your module dependencies and simplify the generation of an executable image see MMS user s guide for further informations There is a description file descrip mms for the module dependencies of the demo application and the default rules for the generation of DBPL code and DBPL symbol files Using MMS it is sufficient to type mms 32 Bibliography ERMS91 J Eder A Rudloff F Matthes and J W Schmidt Data Construction with Recursive JLS85 KMP82 Mod91 MRS84 MRS89 MS89 SBK 88 SEM88a SEM88b SGLJ89 Set Expressions in DBPL In Proceedings of the Kiev East West Workshop on Next Generation Database Technology volume 504 of Lecture Notes in Computer Science April 1991 M Jarke V Linnemann and J W Schmidt Data Constructors On the Integration of Rules and Relations In 11th Intern Conference on Very Large Data Bases Stockholm August 1985 J Koch J Mall and P Putfarken Modula 2 for the VAX Description of a System Portation In H Langmaack B Schlender and J W Sch
3. Application Go to the directory demo set def demo The example application consists of the following files 1 gtypes def and gtypes dbp 2 gdb def a database module and gdb dbp 3 gdoc def and gdoc dbp 31 4 gdisplay def and gdisplay dbp 5 gdemo dbp and gdemo2 dbp the main program modules importing the other modules Compile these modules with dbplc log debug gtypes def dbplc log debug create gdb def dbplc log debug gdoc def dbplc log debug gdisplay def dbplc log debug gtypes mod dbplc log debug gdb mod dbplc log debug gdisplay mod dbplc log debug gdoc mod dbplc log debug gdemo mod dbplc log debug gdemo2 mod CARA AHHH HF HS Please note that the order of these operations is significant since the compiler has to read the symbol files of imported modules during compilation By using the qualifier create the persistent database variables will be created You will therefore find some new files with extensions dat i00 dic in the current default directory These files are needed during subsequent executions of the DBPL application Now link your applications with link debug gdemo obj gtypes obj gdisplay obj gdb obj gdoc obj link debug gdemo2 obj gtypes obj gdisplay obj gdb obj gdoc obj Note that the main module gdemo gdemo2 respectively is at the first position If you use this link command the VAX Debugger will be automatically activated when you start your application If you do not need this feature
4. Local Control of Run Time Checks The insertion of run time checks into the generated code can additionally be controlled during compilation by using the S and T options An option must be entered into the source text at the beginning of a comment clause it has the general form Option Name Switch Name S T Switch p e where the associated switch enables run time checks disables run time checks resets the option to the previous value The option controls subrange checks e g when assigning a value to a variable of a subrange type The T options controls index checks when accessing arrays Examples T to generate test code when accessing arrays T to turn off test code generation S i j S no subrange checks 2 3 Search Strategies In the default case i e when no file name is specified in query mode the compiler applies a standard strategy to search for the symbol files needed The default file name is constructed out of the module s name and the file extension SYM The file is first searched in the user s default directory If the search fails directories with the logical names MOD LIBRARY MOD LIBRARY_1 up to MOD LIBRARY_9 are searched in this order The entire process is performed first in the process logical name table second in the job logical name table then in the group logical name table and finally in the system logical name table Each sear
5. accompanied by symbolic traceback information By default TRACEBACK is enabled DEBUG implies TRACEBACK Summary Link Command Qualifiers Qualifier Negative Form Default BRIEF none not applicable CROSS_REFERENCE NOCROSS_REFERENCE NOCROSS_REFERENCE DEBUG NODEBUG NODEBUG FULL none not applicable Map file spec NOMAP NOMAP interactive MAP batch TRACEBACK NOTRACEBACK TRACEBACK 12 3 3 Identification Checking The VAX DBPL compiler provides identification information for describing the relationship be tween symbol files and object files belonging to the same module This identification is in fact the compilation date and time of the corresponding definition module and it is passed to the linker in the form of an Entity Ident Consistency Check subrecord The linker checks the Entity Ident Consistency Check subrecord of each object module before it links them together If object files of two modules importing different versions of the same definition module are encountered the linker issues a warning message In such a case the object files giving rise to the message should be replaced by newly compiled ones For more information about the Entity Ident Consistency Check subrecords see the VAX 11 Linker Reference Manual 13 Chapter 4 Executing The application program can be started by the RUN command ruN No pEBUG file spec The DEBUG qualifier allows to run the program under
6. compiler If a compilation unit imports objects from module SYSTEM no symbol file has to be supplied for this module Objects exported from module SYSTEM Types BYTE SHORTWORD WORD QUADWORD OCTAWORD Objects of these types represent individually accessible storage units BYTE one byte SHORTWORD two bytes WORD four bytes QUADWORD eight bytes OCTAWORD sixteen bytes Only assignment is allowed for variables of these types A parameter of type BYTE SHORTWORD WORD QUADWORD or OCTAWORD may be substituted by an actual parameter of any type that uses the same number of bytes in storage If the parameter is a value parameter of type BYTE SHORTWORD or WORD then values of types using up to four bytes are also allowed for substitution The same holds for the substitution of an open array parameter with elements of type SHORTWORD WORD QUADWORD or OCTAWORD by a value of a type which size is not an integral multiple of the open array element size For compatibility with the VAX VMS data type names the identifier LONGWORD is also exported from the module SYSTEM as a synonym for the identifier WORD The Modula 2 Standard will support only BYTE and WORD ADDRESS Objects of type ADDRESS represent the byte address of a storage location The type ADDRESS is compatible with all pointer types and is itself defined as POINTER TO WORD All integer arithmetic operators apply to this type This will be changed by the Modula 2 Standard It is
7. control of the debugger even if you have issued the DBPLC and LINK commands without this qualifier NODEBUG will override a DEBUG given at link time In interactive mode the file specification may be entered on a separate line by typing a carriage return after the command name The system responds with a prompt for the file specification 4 1 Debugging the Program Currently the VAX Symbolic Debugger runs DBPL programs with the language mode set to PASCAL See the corresponding chapter of the PASCAL User s Guide or the VAX 11 Sym bolic Debugger Reference Manual for a description Because of the differences between the two languages some features work differently as there are e No distinction is made between lower and upper case letters in identifiers e Nested modules are not recognized all variables and procedures declared inside a nested module are made global to the compilation unit e Module bodies are treated as parameterless procedures with the names of the modules NOTE The differences mentioned above may lead to name conflicts inside the debugger which are not always handled properly e Type CARDINAL is treated as INTEGER e All variables and procedures can only be accessed in the context of the module they are defined in see the debugger commands SET MODULE SET SCOPE e Sets are displayed and must be entered in PASCAL notation using square brackets P e Open array parameters are known to the deb
8. real CARDINAL floating point number unsigned number Other standard functions 27 CAP CHAR CHAR letter to capital ABS numeric numeric absolute value of a whole or floating point number ODD whole BOOLEAN is the whole number odd SIZE var typename whole Returns the number of bytes allocated for the variable or a variable of the specified type If the variable is of a record type with variants then the variant with maximal size is assumed Neither dynamic variables of type ARRAY OF nor dereferenced pointers or elements of records or fields are allowed as arguments Use HIGH or TSIZE instead HIGH dynvar whole highest index of a dynamic variable type ARRAY OF only one dimension is possible LENGTH string whole length of a string which is terminated by the character 0C MAX typename type maximum value of this type MIN typename type minimum value of this type 28 Appendix B Modula 2 DBPL Compiler Installation The DBPL distribution tape contains the DBPL system a compiler and a runtime system as well as a Modula 2 compiler both running under VAX VMS and developed at the University of Hamburg Both compilers are based on the Modula 2 compiler M2RT11 developed at the Institut fur Informatik Eidgen ssische Technische Hochschule Zurich The DBPL compiler is able to utilize the symbolfiles produced by the Modula 2 compiler Using Foreign Definition modules see the Modula 2 User
9. recommended to use no arithmetic with pointers PROCESS Objects of type PROCESS are used for process handling Upon termination of a process other than the main process an exception condition is signaled This type and the corresponding procedures will be separated in another system module called COROUTINES by the Modula 2 Standard F_FLOATING DFLOATING GFLOATING H FLOATING The DBPL standard type REAL is implemented using the VAX F_FLOATING data type the type LONGREAL is implemented by D_FLOATING The other VAX floating point data types are made available in the VAX DBPL compiler through export from module SYSTEM All operators defined in DBPL for the types REAL and LONGREAL are also de fined for the types F_FLOATING D_FLOATING G_FLOATING and H_FLOATING Different floating point types cannot be mixed in expressions i e there is no implicit conver sion However the module Conversions exports procedures for the conversion of the different floating point data types into each other The standard functions TRUNC and INT are applicable to all floating point data types NOTE If your VAX processor is not equipped with the extended instruction set option and you are using variables of type G_FLOATING H_FLOATING or OCTAWORD the 21 VAX extended instruction set emulator LIBSEMULATE should be established as a condition handler See the VAX 11 Run Time Library Reference Manual for more information Procedures NEWPROCESS p PROC a
10. system It does not in volve any actual computation but modifies the compiler s type checking For instance if c is an expression of type CARDINAL then SYSTEM CAST BITSET c is interpreted as the corresponding value of type BITSET This is a correspondence determined by the underlying system and not by the programming language itself Therefore using the type transfer function requires familiarity with the internal representation and storage allocation scheme of the corresponding data types Note The original type transfer of Modula 2 is provided by the type name as function e g BITSET c This will be changed by the Modula 2 Standard The DBPL compiler supports both forms but it is recommended to use SYSTEM CAST 6 1 2 Absolute Addresses The assignment of absolute addresses is still allowed in DBPL but this feature should be used with utmost care because all addresses are usually relocated by the linker The Modula 2 Standard will change this feature 20 6 1 3 The Module SYSTEM The module SYSTEM offers some further facilities of the DBPL language Most of them are imple mentation dependent and or refer to the given processor Facilities of that kind are sometimes necessary for the so called low level programming SYSTEM contains also types and procedures which allow a very basic coroutine handling The module SYSTEM is known to the compiler because its exported objects obey special rules that must be checked by the
11. together to form an executable image file which can be executed by the RUN command 1 2 File Specifications and Defaults A full VAX VMS file specification has the following form node device directory filename filetype version Node device directory and version are optional items their default values are node device directory version applicable only to systems supporting DECnet VAX user s current device user s current default directory highest version on input highest version 1 on output The filetype specification may be omitted in certain cases The default type depends on usage DEF MOD DBP source files input to DBPL compiler SYM symbol file input to and output from DBPL compiler DIC DAT I00 database files output from DBPL compiler OBJ LIS OBJ EXE when creating a database object code file output from DBPL compiler source file listing output from DBPL compiler object code file input to linker executable file output from linker Chapter 2 Compiling Each DBPL compilation unit has to be compiled separately In the case of a definition module a symbol file is created an object file otherwise Optionally a source file listing may be produced The compiler also searches for and reads the symbol files belonging to imported modules If not specified otherwise a standard search strategy is applied see The DBPL compiler is invoked T by the DBPLC or MODULA command which
12. ADDRESS n CARDINAL VAR pi PROCESS Instantiates a new process At least 160 bytes are needed for the workspace of a process This procedure will be put to a new module COROUTINES when the Modula 2 Standard is published TRANSFER VAR p1 p2 PROCESS Transfers control between two processes This procedure will be put to a new module COROUTINES when the Modula 2 Standard is published Functions CAST type expression type The bit representation of expression is interpreted as a value of typename ADR variable ADDRESS Returns the storage address of the variable TSIZE type CARDINAL See below TSIZE type tagiconst tag2const CARDINAL Returns the number of bytes allocated for a variable of the type If the type is a record with variants then tag constants of the last FieldList see DBPL syntax may be substituted in their nesting order If no or not all tag constants are specified then the remaining variant with maximal size is assumed Be careful when using this option because the compiler is not checking if you are using the correct variants REGISTER num CARDINAL CARDINAL Returns the content of the specified register This function applies only to the VAX hardware 6 2 Storage Management 6 2 1 The Module Storage The storage management procedures ALLOCATE and DEALLOCATE which serve to dynamically obtain and return storage space can be imported from the standard module Storage DEFINITION MODULE Storage F
13. D because INTEGER and CARDINAL are already 32 bit long It is recommended to use subrange types of INTEGER and CARDINAL to support portability Standard functions The following standard functions are provided by the current implementation Conversion functions Conversions are only allowed between elementary data types All possible conversions can be done with the function VAL see table VAL typename expression Example intvar VALCINTEGER realvar typename or subrange expr CARDINAL INTEGER REAL LONGREAL CHAR BOOLEAN enum CARDINAL y J Wi INTEGER J J J zz viv v REAL LONGREAL RR CHAR SS1 BOOLEAN enum V V V V v V v v v V v v v v v v v v ZZ is the type for literal INTEGER CARDINAL constants ORR is the type for literal REAL LONGREAL constants SS is the type for literal CHAR ARRAY OF CHAR constants Table A 1 Possible conversions with VAL typename expr Some common conversions are available in a shorter form as explained below CHR whole CHAR whole number character FLOAT numeric REAL whole or floating point number real number short floating point LFLOAT numeric LONGREAL whole or floating point number longreal number long floating point INT all INTEGER whole or floating point number character enumeration or boolean value signed number ORD ordinal CARDINAL whole number character enumeration or boolean value unsigned number TRUNC
14. DBPL Memo 121 91 VAX Modula 2 User s Guide VAX DBPL User s Guide F Matthes J W Schmidt G Schroder This document describes how to compile link and execute Modula 2 programs on a VAX under the VMS operating system The VAX Modula 2 Compiler is based on an implementation of Modula 2 for the PDP 11 developed by a group under the direction of Prof N Wirth at the ETH Zurich This document also describes how to compile link and execute DBPL programs on a VAX under the VMS operating system DBPL is a relational database programming language that has Modula 2 as its algorithmic kernel The DBPL Compiler is a fully upward compatible extension of the VAX Modula 2 Compiler Software Version 2 0 December 1991 Arbeitsbereich DBIS Fachbereich Informatik Universitat Hamburg Schluterstrave 70 D 2000 Hamburg 13 Federal Republic of Germany Contents PREFACE Manual Objectives The VAX Modula 2 User s Guide has been designed to support the development and execution of Modula 2 programs in the VAX VMS environment The Modula 2 language constructs are described in the Modula 2 Report 3rd Edition by N Wirth The compiler also incorporates some extensions proposed in the emerging ISO Modula 2 standard Note for DBPL users The VAX DBPL User s Guide describes the extensions to the VAX Modula 2 compiler that support the development and execution of DBPL database applications in the VAX VMS environment The DBPL language con
15. ROM SYSTEM IMPORT ADDRESS PROCEDURE ALLOCATE VAR p ADDRESS size CARDINAL PROCEDURE DEALLOCATE VAR p ADDRESS size CARDINAL END Storage ALLOCATE signals an exception whenever there is not enough free heap space This will be changed by the Modula 2 Standard ALLOCATE will return NIL if there is not enough heap space 22 When writing your own storage management procedures you should care for an appropriate declaration DEALLOCATE should set p to NIL Since NEW and DISPOSE are translated into calls to ALLOCATE and DEALLOCATE these must be compatible with the type PROCEDURE VAR ADDRESS CARDINAL 6 2 2 Storage Allocation Table summarizes the storage allocation and alignment for variables of unstructured and set type note that word longword quadword and octaword are DEC terms storage allocation alignment boundary BOOLEAN CHAR 8 bits 1 byte byte BYTE 16 bits 1 word BITSET INTEGER CARDINAL F_FLOATING REAL 32 bits 1 longword longword POINTER WORD ADDRESS RELATION SELECTOR CONSTRUCTOR LONGREAL D_FLOATING G_FLOATING 64 bits 1 quadword longword QUADWORD H_FLOATING 128 bits 1 octaword longword OCTAWORD Enumeration 8 bits 1 byte if byte type contains 256 or less elements 16 bits 1 word word if type contains 256 or more elements SET 8 bits 1 byte byte 16 bits 1 word or word 32 bits 1 longword longword according to cardinality o
16. ation optional ao co F amp F WwW N database creation for database modules If the compiler option LOG is specified the succesion of passes mentioned above is displayed A more detailed information about compiler options is given in section VAX VMS Modula 2 symbol files are compatible with DBPL symbol files hence modules written in Modula 2 may also be imported to DBPL programs 2 1 Compiler Command Qualifiers DBPLC resp MODULA command qualifiers control optional compiler settings For every qualifier there is a negative form to suppress the respective effect The negative form is indicated by a leading NO e g NOLIST is the negative form of LIST If you want to change the default values of the qualifiers edit the file DBPLC CLD resp MODULA CLD A default value is marked by the keyword DEFAULT All other values are set by default to NO The meaning of the qualifiers and their default values is listed below CHECK Code is generated to perform run time checks for out of range array bounds and case labels By default CHECK is enabled CREATE A new database is created when compiling a database definition module By default CREATE is disabled CROSS_REFERENCE A cross reference table is included in the source listing This qualifier is effective only when used in conjunction with LIST By default CROSS_REFERENCE is disabled DBPL A DBPL module will be compiled All DBPL enhancement
17. call procedures Each time a procedure is called the DBPL compiler constructs an argument list on the stack The arguments in the list are based on the parameter type and the parameter kind value or reference specified in the formal parameter list and the values in the actual parameter list 5 1 Parameter Passing Mechanisms The VAX procedure calling standard defines three mechanisms by which arguments are passed to procedures 1 by reference 2 by immediate value 3 by descriptor Table describes the mechanisms that are used by the VAX DBPL compiler depending on the type and the kind of the formal parameter An open array parameter is passed by two arguments The parameter list created by the compiler for an open array parameter definition a ARRAY OF type is equivalent to the following foreign parameter definition see below IMMED higha CARDINAL IMMED adra ADDRESS with adra ADR a and higha HIGH a 16 BOOLEAN CHAR INTEGER CARDINAL POINTER SET Enumeration Subrange BYTE by reference by reference SHORTWORD WORD ADDRESS REAL LONGREAL F_FLOATING D_FLOATING G_FLOATING H_FLOATING QUADWORD OCTAWORD RECORD ARRAY RELATION by reference by reference SELECTOR CONSTRUCTOR PROCEDURE by reference mams OOOO S Table 5 1 Parameter passing mechanisms 5 2 Function Return Values A function returns a value to the calling program The method by which a value is returned
18. ch terminates when the first undefined logical name is encountered If the file has not yet been found the directory with the logical name MOD SYSTEM is searched The result of the searching process is displayed to the user when the LOG option is enabled 2 4 Compiler Listing The contents of the listing is controlled by the command qualifiers LIST CROSS_REFERENCE and MACHINE_CODE The application of LIST is necessary to obtain a listing at all Each listing page has a two line heading The first line contains from left to right e the name of the compilation unit e the date of compilation e the compiler version and e a running page number In the second line you will find e the listing subject e the creation date and e the name of the source file The listing terminates with a compilation summary informing about the active compiler op tions and giving some performance data 2 4 1 Source Listing Initiated by LIST The source list contains a copy of the source file preceded by the compiler generated line numbers Error messages are inserted after the erroneous lines The position where an error has been detected is marked by an arrow 2 4 2 Cross Reference Table Initiated by CROSS_REFERENCE presupposes LIST The cross reference table presents all identifiers defined or accessed in the compilation unit in alphabetical order Standard names are not tabulated Each table entry consists of at least two items
19. ction qualident ForeignFPSection VAR REF IMMED STDESCR IdentList FormalType where IMMED denotes passing by immediate value REF denotes passing by reference and STDESCR denotes passing by string descriptor As an example we give a definition module which allows access to some screen handling procedures FOREIGN DEFINITION MODULE CommandLanguagelInterface PROCEDURE CLI PRESENT ASTDESCR entityDesc ARRAY OF CHAR CARDINAL PROCEDURE CLI GET_VALUE 18 ASTDESCR entityDesc ARRAY OF CHAR VAR STDESCR retdesc ARRAY OF CHAR VAR retlength CARDINAL CARDINAL END CommandLanguageInterface Foreign definition modules should not be written without knowledge about the parameter passing mechanisms involved 19 Chapter 6 System Dependent Facilities 6 1 Low Level Facilities There are applications e g system programming for which the language rules may turn out to be too restrictive For this reason DBPL provides some means for low level programming most of them are implementation dependent The programmer is urged to use these low level facilities very carefully and only if it seems unavoidable He will be much less protected against errors because low level facilities are not checked for consistency with language rules 6 1 1 Type Transfer Function The type transfer function SYSTEM CAST serves to breach DBPL s type
20. depends on its type as listed in table 5 3 Foreign Procedures Access to procedures and variables written in other VAX programming languages especially to the VAX VMS system services and Run Time Library procedures is provided through special definition modules so called foreign definition modules They serve only to export the descriptions of the respective procedures and have no corresponding DBPL implementation modules A foreign definition module is syntactically indicated by the prefix AFOREIGN ForeignDefinitionModule FOREIGN DEFINITION MODULE ident import foreigndefinition END ident This section contains the formal definitions of the procedures and variables to be linked Pro 17 BOOLEAN CHAR INTEGER CARDINAL POINTER Enumeration Register RO Subrange BYTE SHORTWORD WORD ADDRESS REAL F_FLOATING LONGREAL D_FLOATING GFLOATING Registers RO R1 QUADWORD H_FLOATING by reference as the first OCTAWORD parameter in the function s parameter list Table 5 2 Function value return methods cedure and variable names must be known to the linker and the calling convention must match at the linker level To allow full utilization of the VAX VMS procedure calling standard additional parameter qualifiers have been introduced applicable only within foreign definition modules ForeignFormalParameters ForeignFPSection ForeignFPSe
21. el 0 1 a 0 2 b Alternative character set The Modula 2 Standard states that an alternative character set has to be supported because the american character set is not always available The following table shows the alternative constructs ASCH Real number conversion The real number conversion routines are implemented according to VAX instructions Le they work with type INTEGER instead of type CARDINAL The results of FLOAT x and LFLOAT x will be wrong if x is a cardinal number outside the range of INTEGER The result of TRUNC x will be wrong if x is a negative number or a positive number outside the INTEGER range Open arrays The maximal length of open arrays is 65536 bytes Only one dimension is allowed FOR statement The step must not be greater than 7FFFFFFFH MAX INTEGER CASE statement The labels of a case statement must not be greater than 7FFFFFFFH Priority specifications Priority specifications are not implemented Standard procedures In contrast to Wirth s 3rd edition of the language report but in accordance with the Modula 2 standard this compiler implements the standard procedures NEW and DISPOSE They are translated into calls to ALLOCATE and DEALLOCATE so these procedures have to defined in the context e g by import from the module Storage 26 Elementary data types As numerical types INTEGER CARDINAL REAL and LONGREAL have been implemented There are no types LONGINT or LONGCAR
22. f base type Table 6 1 Storage allocation and alignment Variables of subrange type are allocated and aligned in the same way as variables of their base type 23 An array is stored and aligned according to the type of its elements Every element is also aligned according to its type Records are stored field by field Each field is allocated according to its type and aligned on a byte boundary T Variables of Type RELATION SELECTOR and CONSTRUCTOR are allocated to one longword and aligned on a longword boundary L 24 Appendix A Restrictions and Extensions The implementation of DBPL on the VAX differs in some respect from the language definition some restrictions have to be considered Most parts of the language follow Wirth s 3rd edition of the language report on Modula 2 Some are taken from the 4th draft proposal of the Modula 2 Standard Identifiers Identifiers may contain the additional characters and _ ident letter letter digit Note The Modula 2 Standard will also allow the underline character in identifiers Due to the naming conventions of the linker some additional restrictions must be obeyed for module names and exported procedure identifiers An external name is at the linker level composed of the module name and the exported name both converted to upper case and separated by a dot If the composed name is longer than 31 characters includin
23. g the dot the individual names are shortened to 15 characters A conflict will occur if the resulting name is not unique anymore The module name of a compilation unit should not contain the additional characters and eae Qualified export Is is possible to restrict exports of a definition module with the statement EXPORT QUALIFIED This language element is obsolete and may be missing in future versions of the DBPL com piler Opaque types According to the Modula 2 standard opaque types should be implemented as pointers The DBPL compiler allows all types of size WORD as implementations of opque types Suspect this feature to be changed String constants The length of string constants is restricted to a maximum of 10000 characters String constants can be concatenated with the operator This will also be in the Modula 2 Standard Aggregates Even in the Modula 2 subset it is possible to use aggregates as value constructors for arrays and records This has been adopted by the Modula 2 standard Example 25 TYPE Rec RECORD x y CARDINAL s ARRAY 0 10 OF CHAR END VAR r Rec r Rec 0 100 Hello In the case of nested records or structured array elements only the outmost type has to be mentioned e g TYPE Arr ARRAY 0 1 OF Rec VAR a Arr a Arr 0 1 a 0 2 b Aggregates can also be used to construct relation values e g TYPE Rel RELATION x y OF Rec VAR r Rel r R
24. grammer For some qualifiers there are also negative forms Refer to the VAX 11 Linker Reference Manual for detailed information 11 3 2 1 Map File Qualifiers The MAP qualifier directs the linker to generate a map file containing a summary of the image s characteristics a list of contributing modules and a list of global symbols and values The qualifier has the form uap file spec where the optional file specification designates the map file The default is a file of type MAP with the name of the first object file By default MAP is disabled for interactive mode and enabled for batch mode In conjunction with MAP the modifying qualifiers BRIEF or FULL and CROSS_REFERENCE may be used BRIEF and FULL define the amount of information included in the map file as follows BRIEF produces a summary of the image s characteristics and a list of contributing modules FULL adds a summary of characteristics of image sections in the linked image to the normal map file CROSS_REFERENCE can be used with MAP or MAP FULL to include cross reference infor mation for global symbols in the map file By default CROSS_REFERENCE is disabled 3 2 2 Debugging and Traceback Qualifiers If the DEBUG qualifier is used the program will always be executed under the control of the debugger You may suppress this by issuing NODEBUG with the RUN command By default DEBUG is disabled The TRACEBACK qualifier is used to have error messages
25. hapter 1 Preliminaries 1 1 Files In general a application is composed of a number of separate modules The first step in creating an application program is to edit the different source files containing the compilation units main modules definition modules and implementation modules NOTE The DBPL compiler distinguishes upper and lower case characters All reserved words and standard names must be capitalized Source files are compiled separately The order in which this has to be done depends on the import export relationships between modules In particular definition modules must be compiled prior to the corresponding implementation modules Six kinds of output files may be produced e Compilation of a definition module yields in a symbol file containing a module descrip tion readable by the compiler This file is needed when the implementation module or a compilation unit importing the module is compiled e The result of processing an implementation or main module is an object file readable by the linker e Compilation of a database definition implementation or main module additionally generates a database dictionary file and several data files and index files for persistent database variables e Optionally a listing file can be produced It contains a listing of the module with error messages A machine code listing and a cross reference table can be included e Finally the separate object files have to be linked
26. has the following form DBPLC qualifier file spec qualifier respectively MODULA qualifier file spec qualifier file spec determines the source file containing the compilation unit Only one file is accepted The default file type is MOD for Modula 2 files command MODULA or qualifier NODBPL and DBP for DBPL files command DBPLC or qualifier DBPL Type DEF is recommended for definition L modules In interactive mode you can also enter the file specification on a separate line by typing a carriage return after you type DBPLC or MODULA The system responds with a prompt for the file specification DBPLC _File On termination the DBPL compiler returns a status code in the reserved global symbols STA TUS and SEVERITY which indicates either a success or a severe error during compilation This information can be used for controlling the execution of VMS command procedures see VAX VMS Guide to Using Command Procedures for details Processing of a source file comprises several passes Temporary work files named INTERFILE DVC serve for interpass communication The normal succession of passes is for definition modules 1 syntax analysis 2 declaration analysis 3 symbol file generation 4 listing generation optional 5 database creation for database definition modules and for implementation and main modules 1 syntax analysis declaration analysis body analysis code generation listing gener
27. midt editors Tagungsband Implementierung Pascal artiger Programmiersprachen Teubner Verlag 1982 in Ger man ISO IEC JTC1 SC22 WG13 Interim Version of the 4th Working Draft Modula 2 Standard 1991 M Mall M Reimer and J W Schmidt Data Selection Sharing and Access Control in a Relational Scenario In M L Brodie J L Myopoulos and J W Schmidt editors On Conceptual Modelling Springer Verlag 1984 F Matthes A Rudloff and J W Schmidt Data and Rule Based Database Program ming in DBPL Esprit Project 892 WP IMP 3 b Fachbereich Informatik Johann Wolfgang Goethe Universitat Frankfurt West Germany March 1989 F Matthes and J W Schmidt The Type System of DBPL In Proceedings of the Second International Workshop on Database Programming Languages Salishan Oregon pages 255 260 June 1989 J W Schmidt M Bittner H Klein H Eckhardt and F Matthes DBPL System The Prototype and its Architecture Esprit Project 892 WP IMP 3 2 Fachbereich In formatik Johann Wolfgang Goethe Universitat Frankfurt West Germany November 1988 J W Schmidt H Eckhardt and F Matthes DBPL Report DBPL Memo 112 88 Fachbereich Informatik Johann Wolfgang Goethe Universitat Frankfurt West Ger many 1988 J W Schmidt H Eckhardt and F Matthes Extensions to DBPL Towards A Type Complete Database Programming Language Esprit Project 892 WP IMP 3 1 Fach bereich Informatik Johann Wolfgang Goethe Universitat Frankfu
28. nstall All files are copied so that you can then delete all files from system 30 Appendix C A Sample DBPL Program The distribution kit of the Modula 2 compiler includes a small DBPL demonstration program This chapter describes how to compile and execute this program Further information on the language DBPL and its use is available on request from Hamburg University These are the general steps required for the development of database applications 1 Create the DBPL source files 2 Compile them with dbplc command_qualifier filename Look at the file MOD SYSTEM dbpl cld for allowed command qualifiers DATABASE MODULE s have to be compiled with the qualifier create to create an uninitialized database Details of the command qualifiers can be found in the VAX DBPL User s Guide The first application program accessing that database will execute the user definable database initialization code for that database 3 Link your objectfiles with link file obj file obj File should be the main program module It is not necessary to name the object libraries of the Modula 2 and DBPL system explicitely 4 Start your application with run file exe For Modula 2 programs you can use the Modula 2 compiler in the same way by compiling this files with mod command_qualifier filename Look at the file MOD SYSTEM modula cl1d for allowed command qualifiers They are also explained in the VAX DBPL User s Guide C 1 An Example
29. rt West Germany April 1988 J W Schmidt L Ge V Linnemann and M Jarke Integrated Fact and Rule Manage ment Based on Database Technology In J W Schmidt and C Thanos editors Founda tions of Knowledge Base Management Topics in Information Systems Springer Verlag 1989 33 SL85 SM90 SM91a SM91b Wir85 J W Schmidt and V Linnemann Higher Level Relational Objects In Proc 4th British National Conference on Databases BNCOD 4 Cambridge University Press July 1985 J W Schmidt and F Matthes Language Technology for Post Relational Data Systems In A Blaser editor Database Systems of the 90s volume 466 of Lecture Notes in Computer Science pages 81 114 November 1990 J W Schmidt and F Matthes Naming Schemes and Name Space Management in the DBPL Persistent Storage System In Proceedings of the Fourth International Workshop on Persistent Object Systems Martha s Vineyard Massachusetts Morgan Kaufmann Publishers January 1991 J W Schmidt and F Matthes The Rationale behind DBPL In 3rd Symposium on Mathematical Fundamentals of Database and Knowledge Base Systems volume 495 of Lecture Notes in Computer Science Springer Verlag May 1991 N Wirth Report on the Programming Language Modula 2 Springer Verlag 3rd edition 1985 34
30. s Guide on tape it is furthermore possible to develop arbitrary mixed language systems with the DBPL compiler Before proceeding with the installation process make sure that you have enough disk space available Approximately 9000 disc blocks are needed to install both compilers and their libraries 1 Create a directory where the compiler should reside create dir modula 2 Step into this directory set default modula 3 Mount the tape mount foreign mua0 4 Copy the files to your directory backup mua0 dbpl bck log 5 Dismount the tape dismount mua0 6 Now you find two sub directories in the directory modula system the compiler and all files needed for runtime including symbol and object files of library modules lib sources of the library definition modules 29 demo sources of a tiny DBPL application 7 Step to the directory system set default system 8 Installation of path names You have two possibilites to install the compiler a INSTALL The compiler resides in this directory and each user has to set some path names to use it install A command procedure STARTUP COM is created which every user has to execute before using the compiler b SYSTEM_INSTALL The compiler and all stuff from system is copied to a system directory and some system path variables are set so that all users can use the compiler without setting own path variables Osystem_i
31. s of Modula 2 are available By default DBPL is enabled when using command DBPLC and disabled when using command MODULA DEBUG The DEBUG qualifier produces information to be used by the VAX Symbolic Debugger and the run time error reporting mechanism By default DEBUG is disabled and only traceback information is generated LIST A listing file is written The qualifier has the general form LIST file spec list You may include a file specification for the listing file If no specification is given a file of type LIS with the name of the source file is created The file contains at least the source text and the error messages but further listings are added by applying CROSS_REFERENCE and or MACHINE_CODE By default LIST is disabled for interactive mode and enabled for batch mode but note that even in batch mode the listing file is not automatically printed LOG If the LOG option is enabled the following information is displayed e compiler version qualifiers applied e succession of the compiler passes and e the names of the symbol files read By default LOG is disabled for interactive mode and enabled for batch mode MACHINE_CODE A readable representation of the generated code is included in the source listing This qualifier is effective only in conjunction with the LIST qualifier By default MACHINE_CODE is disabled OBJECT An object file for the linker is produced The qualifier has the form OBJECT
32. shed via the line numbers inserted as comments on the right hand side 10 Chapter 3 Linking After compilation the separate object modules of the application program are linked together to produce an executable image file 3 1 The Link Command The modules of an application program are linked with the normal LINK command LINK command qualifiers file spec list command qualifiers Specify output file options file spec list Specifies the input files to be linked File specifications can be separated by commas or plus signs To create executable code you must specify all your object files to be linked except the ones stored in the default link libraries The first file named should contain the main program module By default object files are assumed to be of type OBJ If some or all of the object files reside in a library you can specify this library with the qualifier LIB e g MYLIB LIB The linker will automatically search these libraries for the needed files The default file type for object libraries is OLB If no other specification is given the executable image file takes the name of the first object file and is of type EXE In interactive mode you may enter the file specifications on a separate line by typing a carriage return after the command name The system responds with a prompt for the file specification 3 2 Linker Command Qualifiers Below a few qualifiers are listed which may be of interest to the DBPL pro
33. structs are described in the Report on the Database Programming Language DBPL Further documentation and publications on DBPL are available through Hamburg University see also references in the bibliography Intended Audience This manual is intended for programmers who have a general knowledge of the VAX VMS Com mand Language and the DBPL programming language In some sections a more detailed un derstanding of the operating system is required The reader should consult the corresponding manuals for the information needed Related Documents VAX 11 Symbolic Debugger Reference Manual VAX 11 Linker Reference Manual VAX 11 Architecture Handbook VAX 11 PASCAL User s Guide VAX 11 Run Time Library Reference Manual VAX VMS System Services Reference Manual Notational Conventions Within command language descriptions large square brackets indicate that the enclosed sequence of symbols is optional braces indicate that the enclosed sequence of symbols may be repeated zero or more times Parts of the text which apply to extensions of the compiler that are needed to use it as a DBPL rather than a Modula 2 compiler are marked by T and L DBPL and Modula 2 DBPL is an extended version true superset of Modula 2 The VAX DBPL compiler accepts both DBPL and Modula 2 modules So you can replace the term DBPL by Modula 2 in the following text Parts that apply only to DBPL modules are marked by T and L C
34. the identifier and its declaration class The latter distinguishes constants types variables parameters value and variable fields procedures functions and modules Further specifications which may follow are A short type characterization enclosed in angle brackets For subranges the base type is denoted if the type has been denoted by a synonym the original type name is given This item is omitted for hidden types predefined types procedures and modules e The name of the scope in which the identifier is defined preceded by in or from This item is omitted when the name is defined at global level The prefix from indicates that the defining scope is external Alternatively the word imported may appear if the name designates an external module in this case the full symbol file name is also given e The word exported which means that the identifier is exported from the enclosing module e A list of numbers of the lines where the name is referenced A definition line is marked by an asterisk Included in the table are also identifiers imported indirectly as part of another imported identifier although they are not referenced in the source text There is of course no list of line numbers in this case 2 4 3 Machine Code Listing Initiated by MACHINE_CODE presupposes LIST The generated code is represented as a VAX MACRO program source listing Correspondence with the source text is establi
35. ugger as fixed size arrays with a lower bound of 0 and an upper bound of 2 x16 1 14 e Constant and type identifiers are not known to the debugger e All tagfields and fields in record variants are known as ordinary record fields to the debugger i e the tagfield and variant information is not present DBPL transactions are provided with a special condition handler which enforces an abort of the current transaction if a severe runtime condition is signalled As a result the debugger usually does not catch transaction failures You may direct the debugger to treat transaction failures also by issuing the SET BREAK EXCEPTION command NOTE Debugging a transaction may cause the delay of concurrent transactions started by other users 15 Chapter 5 Procedure Calling Conventions In the context of the VAX VMS operating system a procedure is a routine entered by a CALL instruction In a DBPL program such a routine can be a function or a procedure written in DBPL a VAX VMS system service or a VAX Run Time Library procedure This chapter provides information on the calling conventions used by the VAX DBPL compiler and on calling VAX VMS system services and VAX Run Time Library procedures A basic knowledge of the VAX procedure calling and argument passing mechanisms is assumed For more information see the VAX 11 Run Time Library Reference Manual and the VAX 11 Architecture Handbook VAX DBPL uses the VAX CALLS instruction to
Download Pdf Manuals
Related Search