1 GCC The GCC command invokes the GNU C compiler. GCC file-spec 2 Parameters file-spec A C source file. If no input file extension is specified, GNU C assumes .C as the default extension unless the /PLUS qualifier is given, in which case .CC is assumed as the default extension. If an extension of .CPP is given, then the source file is assumed to be the output of the preprocessor, and thus the preprocessor is not executed. If an extension of .S is given, then the source file is assumed to be the assembly code output of the compiler, and only the assembler is called to generate an object file. 2 Qualifiers GNU C command qualifiers modify the way the compiler handles the compilation. The following is the list of available qualifiers for GNU C: /CASE_HACK /CC1_OPTIONS=(option [,option...]]) /DEBUG /DEFINE=(identifier[=definition][,...]) /G_FLOAT /INCLUDE_DIRECTORY=(path [,path...]]) /LIST[=filename] /MACHINE_CODE /OBJECT[=filename] /OPTIMIZE /PLUS /PROFILE[=identifier] /SCAN=(file[,file...]) /SHOW[=option] /UNDEFINE=(identifier[,identifier,...]) /VERBOSE /VERSION /WARNING 2 Linking When linking programs compiled with GNU C, you should include the GNU C library before the VAX C library. For example, LINK object-file,GNU_CC:GCCLIB/LIB,SYS$LIBRARY:VAXCRTL/LIB You can also link your program with the shared VAX C library. This can reduce the size of the .EXE file, as well as make it smaller when it's running. For example, $ LINK object-file, GNU_CC:GCCLIB/LIB,SYS$INPUT/OPT SYS$SHARE:VAXCRTL/SHARE (If you use the second example and type it in by hand, be sure to type ^Z after the last carriage return). A simpler alternative would be to place the single line: SYS$SHARE:VAXCRTL/SHARE into a file called VAXCRTL.OPT, and then use the link command: $ LINK object-file, GNU_CC:GCCLIB/LIB,VAXCRTL.OPT/OPT If a program has been compiled with /G_FLOAT, then the linking instructions are slightly different. If you are linking with the non-shared library, then the command that you should use would be: LINK object-file,GNU_CC:GCCLIB/LIB,SYS$LIBRARY:VAXCRTLG/LIB - ,SYS$LIBRARY:VAXCRTL/LIB Note that both VAXCRTL and VAXCRTLG must be linked to. If you are using the shared VAX C library, then you should use a command like: $ LINK object-file, GNU_CC:GCCLIB/LIB,SYS$INPUT:/OPTIONS SYS$SHARE:VAXCRTLG/SHARE In the case of the sharable library, only one library needs to be linked to. 2 /CASE_HACK /[NO]CASE_HACK D=/CASE_HACK Since the VMS Linker and Librarian are not case sensitive with respect to symbol names, a "case-hack" is appended to a symbol name when the symbol contains upper case characters. There are cases where this is undesirable, (mainly when using certain applications where modules have been precompiled, perhaps in another language) and we want to compile without case hacking. In these cases the /NOCASE_HACK switch disables case hacking. 2 /CC1_OPTIONS This specifies additional switches to the compiler itself which cannot be set by means of the compiler driver. 2 /DEBUG /DEBUG includes additional information in the object file output so that the program can be debugged with the VAX Symbolic Debugger. To use the debugger it is also necessary to link the debugger to your program, which is done by specifying the /DEBUG qualifier to the link command. With the debugger it is possible to set breakpoints, examine variables, and set variables to new values. See the VAX Symbolic Debugger manual for more information, or type "HELP" from the debugger prompt. 2 /DEFINE /DEFINE=(identifier[=definition][,...]) /DEFINE defines a string or macro ('definition') to be substituted for every occurrence of a given string ('identifier') in a program. It is equivalent to the #define preprocessor directive. All definitions and identifiers are converted to uppercase unless they are in quotation marks. The simple form of the /DEFINE qualifier: /DEFINE=vms results in a definition equivalent to the preprocessor directive: #define VMS 1 You must enclose macro definitions in quotation marks, as in this example: /DEFINE="C(x)=((x) & 0xff)" This definition is the same as the preprocessor definition: #define C(x) ((x) & 0xff) If more than one /DEFINE is present on the GCC command line, only the last /DEFINE is used. If both /DEFINE and /UNDEFINE are present on a command line, /DEFINE is evaluated before /UNDEFINE. 2 /G_FLOAT Instructs the compiler to use "G" floating point arithmetic instead of "D". The difference is that double precision has a range of approximately +/-0.56e-308 to +/-0.9 e+308, with approximately 15 decimal digits precision. "D" floating point has the same range as single precision floating point, with approximately 17 decimal digits precision. If you use the /G_FLOAT qualifier, the linking instructions are different. See "Linking" for further details. 2 /LIST /LIST[=list_file_name] This does not generate a listing file in the usual sense, however it does direct the compiler to save the preprocessor output. If a file is not specified, then this output is written into a file with the same name as the source file and an extension of .CPP. 2 /INCLUDE_DIRECTORY /INCLUDE_DIRECTORY=(path [,path...]) The /INCLUDE_DIRECTORY qualifier provides additional directories to search for user-defined include files. 'path' can be either a logical name or a directory specification. There are two forms for specifying include files - #include "file-spec" and #include <file-spec>. For the #include "file-spec" form, the search order is: 1. The directory containing the source file. 2. The directories in the /INCLUDE qualifier (if any). 3. The directory (or directories) specified in the logical name GNU_CC_INCLUDE. 4. The directory (or directories) specified in the logical name SYS$LIBRARY. For the #include <file-spec> form, the search order is: 1. The directories specified in the /INCLUDE qualifier (if any). 2. The directory (or directories) specified in the logical name GNU_CC_INCLUDE. 3. The directory (or directories) specified in the logical name SYS$LIBRARY. 2 /MACHINE_CODE Tells GNU C to output the machine code generated by the compiler. The machine code is output to a file with the same name as the input file, with the extension .S. An object file is still generated, unless /NOOBJ is also specified. 2 /OBJECT /OBJECT[=filename] /NOOBJECT Controls whether or not an object file is generated by the compiler. 2 /OPTIMIZE /[NO]OPTIMIZE Controls whether optimization is performed by the compiler. By default, optimization is on. /NOOPTIMIZE turns optimization off. 2 /PLUS Instructs the compiler driver to use the GNU-C++ compiler instead of the GNU-C compiler. Note that the default extension of source files is .CC when this qualifier is in effect. 2 /PROFILE /PROFILE[=identifier] Instructs the compiler to generate function profiling code. You must link your program to the profiler when you use this options. The profile statistics are automatically printed out on the terminal during image exit. (i.e. no modifications to your source file are required in order to use the profiler). There are three identifiers that can be used with the /PROFILE switch. These are ALL, FUNCTION, and BLOCK. If /PROFILE is given without an identifier, then FUNCTION is assumed. 3 Block_Profiler The block profiler counts how many times control of the program passes certain points in your program. This is useful in determining which portions of a program would benefit from recoding for optimization. The report for the block profiler contains the function name, file name, PC, and the source file line number as well as the count of how many times control has passed through the specified source line. 3 Function_Profiler The function profiler counts how many times each function is entered, and keeps track of how much CPU time is used within each function. You should be careful about interpreting the results of profiles where there are inline functions. When a function is included as inline, then there is no call to the internal data collection routine used by the profiler, and thus there will be no record of this function being called. The compiler does generate a callable version of each inline function, and if this called version is used, then the profiler's data collection routine will be called. 2 /SCAN /SCAN=(file[,file...]) This qualifier supplies a list of files that will be read as input, and the output will be discarded before processing the regular input file. Because the output generated from the files is discarded, the only effect of this qualifier is to make the macros defined in the files available for use in the main input. 2 /SHOW /SHOW[=option] This causes the preprocessor to generate information other than the preprocessed input file. When this qualifier is used, no assembly code and no object file is generated. The output of the preprocessor is placed in the file specified by the /LIST qualifier, if present. If the /LIST qualifier is not present, then the output is placed in a file with the same name as the input file with an extension that depends upon which option that is selected. 3 DEFINITIONS This option causes the preprocessor to dump a list of all of the definitions to the output file. This is useful for debugging purposes, since it lets you determine whether or not everything has been defined properly. If the default file name is used for the output, the extension will be .DEF. 3 RULES This option causes the preprocessor to output a rule suitable for MAKE, describing the dependencies of the main source file. The preprocessor outputs one MAKE rule containing the object file name for that source file, a colon, and the names of all the concluded files. If there are many included files then the rule is split into several lines using the '\'-newline. When using this option, only files included with the "#include "file" directive are mentioned. If the default file name is used for the output, a null extension will be used. 3 ALL This option is similar to RULES, except that it also mentions files included with the "#include <file.h>" directive. If the default file name is used for the output, a null extension will be used. 2 /UNDEFINE /UNDEFINE cancels a macro definition. Thus, it is the same as the #undef preprocessor directive. If more than one /UNDEFINE is present on the GCC command line, only the last /UNDEFINE is used. If both /DEFINE and /UNDEFINE are present on a command line, /DEFINE is evaluated before /UNDEFINE. 2 /VERBOSE Controls whether the user sees the invocation command strings for the preprocessor, compiler, and assembler. The compiler also outputs some statistics on time spent in its various phases. 2 /VERSION Causes the preprocessor and the compiler to identify themselves by their version numbers, and in the case of the compiler, the version number of the compiler that built it. 2 /WARNING When this qualifier is present, warnings about usage that should be avoided are given by the compiler. For more information, see "Using and Porting the GNU Compiler Collection (GCC)", in the section on command line options, under "-Wall". Warnings are also generated by the preprocessor when this qualifier is given. 2 Known_Incompatibilities_with_VAX-C There are several known incompatibilities between GNU-C and VAX-C. Some common ones will be briefly described here. A complete description can be found in "Using and Porting the GNU Compiler Collection (GCC)" in the chapter entitled "Using GCC on VMS". GNU-C provides case hacking as a means of giving case sensitivity to symbol names. The case hack is a hexadecimal number appended to the symbol name, with a bit being set for each upper case letter. Symbols with all lower case, or symbols that have a dollar sign ("$") are not case hacked. There are times that this is undesirable, namely when you wish to link your program against a precompiled library which was compiled with a non-GNU-C compiler. X-windows (or DECWindows) is an example of this. In these instances, the /NOCASE_HACK switch should be used. If you require case hacking in some cases, but not in others (i.e. Libg++ with DECWindows), then it is recommended that you develop a header file which will define all mixed case functions that should not have a case hack as the lower case equivalents. GNU-C does not provide the globaldef and globalref mechanism which is used by VAX-C to coerce the VMS linker to include certain object modules from a library. There are assembler hacks, which are available to the user through the macros defined in gnu_hacks.h, which effectively give you the ability to perform these functions. While not syntactically identical, they do provide most of the functionality. Note that globaldefs of enums is not supported in the way that it is under VAX-C. This can be easily simulated, however, by globaldefing an integer variable, and then globalvaluing all of the enumerated states. Furthermore, the way that globalvalue is currently implemented, the data type of the globalvalue variable is seen to the compiler to be a pointer to the data type that you specify. This is necessary in order to make the compiler correctly address the globalvalue variables.