1M2(1)                                 GNU                                M2(1)
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NAME

6       gm2 - The GNU Modula-2 Compiler
7

SYNOPSIS

DESCRIPTION

OPTIONS

11       For any given input file, the file name suffix determines what kind of
12       compilation is done.  The following kinds of input file names are
13       supported:
14
15       file.mod
16           Modula-2 implementation or program source files.  See the -fmod=
17           option if you wish to compile a project which uses a different
18           source file extension.
19
20       file.def
21           Modula-2 definition module source files.  Definition modules are
22           not compiled separately, in GNU Modula-2 definition modules are
23           parsed as required when program or implementation modules are
24           compiled.  See the -fdef= option if you wish to compile a project
25           which uses a different source file extension.
26
27       You can specify more than one input file on the gm2 command line,
28
29       "-g"
30           create debugging information so that debuggers such as gdb can
31           inspect and control executable.
32
33       "-I"
34           used to specify the search path for definition and implementation
35           modules.  An example is:  "gm2 -g -c -I.:../../libs foo.mod".  If
36           this option is not specified then the default path is added which
37           consists of the current directory followed by the appropriate
38           language dialect library directories.
39
40       "-fauto-init"
41           turns on auto initialization of pointers to NIL.  Whenever a block
42           is created all pointers declared within this scope will have their
43           addresses assigned to NIL.
44
45       "-fbounds"
46           turns on run time subrange, array index and indirection via "NIL"
47           pointer checking.
48
49       "-fcase"
50           turns on compile time checking to check whether a "CASE" statement
51           requires an "ELSE" clause when on was not specified.
52
53       "-fcpp"
54           preprocess the source with cpp -lang-asm -traditional-cpp For
55           further details about these options If -fcpp is supplied then all
56           definition modules and implementation modules which are parsed will
57           be prepossessed by cpp.
58
59       "-fdebug-builtins"
60           call a real function, rather than the builtin equivalent.  This can
61           be useful for debugging parameter values to a builtin function as
62           it allows users to single step code into a real function.
63
64       "-fdef="
65           recognize the specified suffix as a definition module filename.
66           The default implementation and module filename suffix is .def.  If
67           this option is used GNU Modula-2 will still fall back to this
68           default if a requested definition module is not found.
69
70       "-fdump-system-exports"
71           display all inbuilt system items.  This is an internal command line
72           option.
73
74       "-fexceptions"
75           turn on exception handling code.  By default this option is on.
76           Exception handling can be disabled by -fno-exceptions and no
77           references are made to the run time exception libraries.
78
79       "-fextended-opaque"
80           allows opaque types to be implemented as any type.  This is a GNU
81           Modula-2 extension and it requires that the implementation module
82           defining the opaque type is available so that it can be resolved
83           when compiling the module which imports the opaque type.
84
85       "-ffloatvalue"
86           turns on run time checking to check whether a floating point number
87           is about to exceed range.
88
89       "-fgen-module-list=filename"
90           attempt to find all modules when linking and generate a module
91           list.  If the filename is - then the contents are not written and
92           only used to force the linking of all module ctors.  This option
93           cannot be used if -fuse-list= is enabled.
94
95       "-findex"
96           generate code to check whether array index values are out of
97           bounds.  Array index checking can be disabled via -fno-index.
98
99       "-fiso"
100           turn on ISO standard features.  Currently this enables the ISO
101           "SYSTEM" module and alters the default library search path so that
102           the ISO libraries are searched before the PIM libraries.  It also
103           effects the behavior of "DIV" and "MOD" operators.
104
105       "-flibs="
106           modifies the default library search path.  The libraries supplied
107           are: m2pim, m2iso, m2min, m2log and m2cor.  These map onto the
108           Programming in Modula-2 base libraries, ISO standard libraries,
109           minimal library support, Logitech compatible library and
110           Programming in Modula-2 with coroutines.  Multiple libraries can be
111           specified and are comma separated with precedence going to the
112           first in the list.  It is not necessary to use -flibs=m2pim or
113           -flibs=m2iso if you also specify -fpim, -fpim2, -fpim3, -fpim4 or
114           -fiso.  Unless you are using -flibs=m2min you should include m2pim
115           as the they provide the base modules which all other dialects
116           utilize.  The option -fno-libs=- disables the gm2 driver from
117           modifying the search and library paths.
118
119       "-static-libgm2"
120           On systems that provide the m2 runtimes as both shared and static
121           libraries, this option forces the use of the static version.
122
123       "-fm2-g"
124           improve the debugging experience for new programmers at the expense
125           of generating "nop" instructions if necessary to ensure single
126           stepping precision over all code related keywords.  An example of
127           this is in termination of a list of nested "IF" statements where
128           multiple "END" keywords are mapped onto a sequence of "nop"
129           instructions.
130
131       "-fm2-lower-case"
132           render keywords in error messages using lower case.
133
134       "-fm2-pathname="
135           specify the module mangled prefix name for all modules in the
136           following include paths.
137
138       "-fm2-pathnameI"
139           for internal use only: used by the driver to copy the user facing
140           -I option.
141
142       "-fm2-plugin"
143           insert plugin to identify run time errors at compile time (default
144           on).
145
146       "-fm2-prefix="
147           specify the module mangled prefix name.  All exported symbols from
148           a definition module will have the prefix name.
149
150       "-fm2-statistics"
151           generates quadruple information: number of quadruples generated,
152           number of quadruples remaining after optimization and number of
153           source lines compiled.
154
155       "-fm2-strict-type"
156           experimental flag to turn on the new strict type checker.
157
158       "-fm2-whole-program"
159           compile all implementation modules and program module at once.
160           Notice that you need to take care if you are compiling different
161           dialect modules (particularly with the negative operands to
162           modulus).  But this option, when coupled together with "-O3", can
163           deliver huge performance improvements.
164
165       "-fmod="
166           recognize the specified suffix as implementation and module
167           filenames.  The default implementation and module filename suffix
168           is .mod.  If this option is used GNU Modula-2 will still fall back
169           to this default if it needs to read an implementation module and
170           the specified suffixed filename does not exist.
171
172       "-fnil"
173           generate code to detect accessing data through a "NIL" value
174           pointer.  Dereferencing checking through a "NIL" pointer can be
175           disabled by -fno-nil.
176
177       "-fpim"
178           turn on PIM standard features.  Currently this enables the PIM
179           "SYSTEM" module and determines which identifiers are pervasive
180           (declared in the base module).  If no other -fpim[234] switch is
181           used then division and modulus operators behave as defined in PIM4.
182
183       "-fpim2"
184           turn on PIM-2 standard features.  Currently this removes "SIZE"
185           from being a pervasive identifier (declared in the base module).
186           It places "SIZE" in the "SYSTEM" module.  It also effects the
187           behavior of "DIV" and "MOD" operators.
188
189       "-fpim3"
190           turn on PIM-3 standard features.  Currently this only effects the
191           behavior of "DIV" and "MOD" operators.
192
193       "-fpim4"
194           turn on PIM-4 standard features.  Currently this only effects the
195           behavior of "DIV" and "MOD" operators.
196
197       "-fpositive-mod-floor-div"
198           forces the "DIV" and "MOD" operators to behave as defined by PIM4.
199           All modulus results are positive and the results from the division
200           are rounded to the floor.
201
202       "-fpthread"
203           link against the pthread library.  By default this option is on.
204           It can be disabled by -fno-pthread.  GNU Modula-2 uses the GCC
205           pthread libraries to implement coroutines (see the SYSTEM
206           implementation module).
207
208       "-frange"
209           generate code to check the assignment range, return value range set
210           range and constructor range.  Range checking can be disabled via
211           -fno-range.
212
213       "-freturn"
214           generate code to check that functions always exit with a "RETURN"
215           and do not fall out at the end.  Return checking can be disabled
216           via -fno-return.
217
218       "-fruntime-modules="
219           specify, using a comma separated list, the run time modules and
220           their order.  These modules will initialized first before any other
221           modules in the application dependency.  By default the run time
222           modules list is set to "m2iso:RTentity,m2iso:Storage,m2iso:SYSTEM,"
223           "m2iso:M2RTS,m2iso:RTExceptions,m2iso:IOLink".  Note that these
224           modules will only be linked into your executable if they are
225           required.  Adding a long list of dependent modules will not effect
226           the size of the executable it merely states the initialization
227           order should they be required.
228
229       "-fscaffold-dynamic"
230           the option ensures that gm2 will generate a dynamic scaffold
231           infrastructure when compiling implementation and program modules.
232           By default this option is on.  Use -fno-scaffold-dynamic to turn it
233           off or select -fno-scaffold-static.
234
235       "-fscaffold-c"
236           generate a C source scaffold for the current module being compiled.
237
238       "-fscaffold-c++"
239           generate a C++ source scaffold for the current module being
240           compiled.
241
242       "-fscaffold-main"
243           force the generation of the main function.  This is not necessary
244           if the -c is omitted.
245
246       "-fscaffold-static"
247           the option ensures that gm2 will generate a static scaffold within
248           the program module.  The static scaffold consists of sequences of
249           calls to all dependent module initialization and finalization
250           procedures.  The static scaffold is useful for debugging and single
251           stepping the initialization blocks of implementation modules.
252
253       "-fshared"
254           generate a shared library from the module.
255
256       "-fsoft-check-all"
257           turns on all run time checks.  This is the same as invoking GNU
258           Modula-2 using the command options "-fnil" "-frange" "-findex"
259           "-fwholevalue" "-fwholediv" "-fcase" "-freturn".
260
261       "-fsources"
262           displays the path to the source of each module.  This option can be
263           used at compile time to check the correct definition module is
264           being used.
265
266       "-fswig"
267           generate a swig interface file.
268
269       "-funbounded-by-reference"
270           enable optimization of unbounded parameters by attempting to pass
271           non "VAR" unbounded parameters by reference.  This optimization
272           avoids the implicit copy inside the callee procedure.  GNU Modula-2
273           will only allow unbounded parameters to be passed by reference if,
274           inside the callee procedure, they are not written to, no address is
275           calculated on the array and it is not passed as a "VAR" parameter.
276           Note that it is possible to write code to break this optimization,
277           therefore this option should be used carefully.  For example it
278           would be possible to take the address of an array, pass the address
279           and the array to a procedure, read from the array in the procedure
280           and write to the location using the address parameter.
281
282           Due to the dangerous nature of this option it is not enabled when
283           the -O option is specified.
284
285       "-fuse-list=filename"
286           if -fscaffold-static is enabled then use the file filename for the
287           initialization order of modules.  Whereas if -fscaffold-dynamic is
288           enabled then use this file to force linking of all module ctors.
289           This option cannot be used if -fgen-module-list= is enabled.
290
291       "-fwholediv"
292           generate code to detect whole number division by zero or modulus by
293           zero.
294
295       "-fwholevalue"
296           generate code to detect whole number overflow and underflow.
297
298       "-Wcase-enum"
299           generate a warning if a "CASE" statement selects on an enumerated
300           type expression and the statement is missing one or more "CASE"
301           labels.  No warning is issued if the "CASE" statement has a default
302           "ELSE" clause.  The option -Wall will turn on this flag.
303
304       "-Wuninit-variable-checking"
305           issue a warning if a variable is used before it is initialized.
306           The checking only occurs in the first basic block in each
307           procedure.  It does not check parameters, array types or set types.
308
309       "-Wuninit-variable-checking=all,known,cond"
310           issue a warning if a variable is used before it is initialized.
311           The checking will only occur in the first basic block in each
312           procedure if known is specified.  If cond or all is specified then
313           checking continues into conditional branches of the flow graph.
314           All checking will stop when a procedure call is invoked or the top
315           of a loop is encountered.  The option -Wall will turn on this flag
316           with -Wuninit-variable-checking=known.  The
317           -Wuninit-variable-checking=all will increase compile time.
318

SEE ALSO

320       gpl(7), gfdl(7), fsf-funding(7), gcc(1) and the Info entries for gm2
321       and gcc.
322
324       Copyright (c) 1999-2023 Free Software Foundation, Inc.
325
326       Permission is granted to copy, distribute and/or modify this document
327       under the terms of the GNU Free Documentation License, Version 1.3 or
328       any later version published by the Free Software Foundation; with no
329       Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
330       copy of the license is included in the man page gfdl(7).
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334gcc-13                            2023-10-11                             M2(1)
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