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1 perry 1 G++
2 !!!G++
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 OPTIONS
7 PRAGMAS
8 FILES
9 SEE ALSO
10 BUGS
11 COPYING
12 AUTHORS
13 ----
14 !!NAME
15
16
17 g++ - GNU project C++ Compiler
18 !!SYNOPSIS
19
20
21 g++ __[[__''option'' | ''filename''
22 ]...
23 !!DESCRIPTION
24
25
26 The C and C++ compilers are integrated; __g++__ is a
27 script to call __gcc with options to recognize C++. gcc__
28 processes input files through one or more of four stages:
29 preprocessing, compilation, assembly, and linking. This man
30 page contains full descriptions for ''only'' C++ specific
31 aspects of the compiler, though it also contains summaries
32 of some general-purpose options. For a fuller explanation of
33 the compiler, see __gcc__(__1__).
34
35
36 C++ source files use one of the suffixes `__.C__',
37 `__.cc__', `__.cxx__', `__.cpp__', or
38 `__.c++__'; preprocessed C++ files use the suffix
39 `__.ii__'.
40 !!OPTIONS
41
42
43 There are many command-line options, including options to
44 control details of optimization, warnings, and code
45 generation, which are common to both __gcc__ and
46 __g++__. For full information on all options, see
47 __gcc__(__1__).
48
49
50 Options must be separate: `__-dr__' is quite different
51 from `__-d -r__ '.
52
53
54 Most `__-f__' and `__-W__' options have two contrary
55 forms: __-f__''name'' and __-fno-__''name'' (or
56 __-W__''name'' and __-Wno-__''name''). Only the
57 non-default forms are shown here.
58
59
60 __-c__
61
62
63 Compile or assemble the source files, but do not link. The
64 compiler output is an object file corresponding to each
65 source file.
66
67
68 __-D__''macro''
69
70
71 Define macro ''macro'' with the string `__1__' as its
72 definition.
73
74
75 __-D__''macro''__=__''defn''
76
77
78 Define macro ''macro'' as ''defn''.
79
80
81 __-E__
82
83
84 Stop after the preprocessing stage; do not run the compiler
85 proper. The output is preprocessed source code, which is
86 sent to the standard output.
87
88
89 __-fall-virtual__
90
91
92 Treat all possible member functions as virtual, implicitly.
93 All member functions (except for constructor functions and
94 __new__ or __delete__ member operators) are treated as
95 virtual functions of the class where they
96 appear.
97
98
99 This does not mean that all calls to these member functions
100 will be made through the internal table of virtual
101 functions. Under some circumstances, the compiler can
102 determine that a call to a given virtual function can be
103 made directly; in these cases the calls are direct in any
104 case.
105
106
107 __-fdollars-in-identifiers__
108
109
110 Permit the use of `__$__' in identifiers. Traditional C
111 allowed the character `__$__' to form part of
112 identifiers; by default, GNU C also allows this. However,
113 ANSI C forbids `__$__' in identifiers, and GNU C++ also
114 forbids it by default on most platforms (though on some
115 platforms it's enabled by default for GNU C++ as
116 well).
117
118
119 __-felide-constructors__
120
121
122 Use this option to instruct the compiler to be smarter about
123 when it can elide constructors. Without this flag, GNU C++
124 and cfront both generate effectively the same code
125 for:
126
127
128 A foo ();
129 A x (foo ()); // x initialized by `foo ()', no ctor
130 called
131 A y = foo (); // call to `foo ()' heads to temporary,
132 // y is initialized from the temporary.
133
134
135 Note the difference! With this flag, GNU C++ initializes
136 `__y__' directly from the call to __foo ()__ without
137 going through a temporary.
138
139
140 __-fenum-int-equiv__
141
142
143 Normally GNU C++ allows conversion of __enum__ to
144 __int__, but not the other way around. Use this option if
145 you want GNU C++ to allow conversion of __int__ to
146 __enum__ as well.
147
148
149 __-fexternal-templates__
150
151
152 Produce smaller code for template declarations, by
153 generating only a single copy of each template function
154 where it is defined. To use this option successfully, you
155 must also mark all files that use templates with either
156 `__#pragma implementation__' (the definition) or
157 `__#pragma interface__' (declarations).
158
159
160 When your code is compiled with
161 `__-fexternal-templates__', all template instantiations
162 are external. You must arrange for all necessary
163 instantiations to appear in the implementation file; you can
164 do this with a __typedef__ that references each
165 instantiation needed. Conversely, when you compile using the
166 default option `__-fno-external-templates__', all
167 template instantiations are explicitly
168 internal.
169
170
171 __-fno-gnu-linker__
172
173
174 Do not output global initializations (such as C++
175 constructors and destructors) in the form used by the GNU
176 linker (on systems where the GNU linker is the standard
177 method of handling them). Use this option when you want to
178 use a non-GNU linker, which also requires using the
179 __collect2__ program to make sure the system linker
180 includes constructors and destructors. (__collect2__ is
181 included in the GNU CC distribution.) For systems which
182 ''must'' use __collect2__, the compiler driver
183 __gcc__ is configured to do this
184 automatically.
185
186
187 __-fmemoize-lookups__
188
189
190 __-fsave-memoized__
191
192
193 These flags are used to get the compiler to compile programs
194 faster using heuristics. They are not on by default since
195 they are only effective about half the time. The other half
196 of the time programs compile more slowly (and take more
197 memory).
198
199
200 The first time the compiler must build a call to a member
201 function (or reference to a data member), it must (1)
202 determine whether the class implements member functions of
203 that name; (2) resolve which member function to call (which
204 involves figuring out what sorts of type conversions need to
205 be made); and (3) check the visibility of the member
206 function to the caller. All of this adds up to slower
207 compilation. Normally, the second time a call is made to
208 that member function (or reference to that data member), it
209 must go through the same lengthy process again. This means
210 that code like this
211
212
213 cout
214
215
216 makes six passes through all three steps. By using a
217 software cache, a ``hit'' significantly reduces this cost.
218 Unfortunately, using the cache introduces another layer of
219 mechanisms which must be implemented, and so incurs its own
220 overhead. `__-fmemoize-lookups__' enables the software
221 cache.
222
223
224 Because access privileges (visibility) to members and member
225 functions may differ from one function context to the next,
226 __g++__ may need to flush the cache. With the
227 `__-fmemoize-lookups__' flag, the cache is flushed after
228 every function that is compiled. The `-fsave-memoized' flag
229 enables the same software cache, but when the compiler
230 determines that the context of the last function compiled
231 would yield the same access privileges of the next function
232 to compile, it preserves the cache. This is most helpful
233 when defining many member functions for the same class: with
234 the exception of member functions which are friends of other
235 classes, each member function has exactly the same access
236 privileges as every other, and the cache need not be
237 flushed.
238
239
240 __-fno-default-inline__
241
242
243 Do not make member functions inline by default merely
244 because they are defined inside the class scope. Otherwise,
245 when you specify __-O__, member functions defined inside
246 class scope are compiled inline by default; i.e., you don't
247 need to add `__inline__' in front of the member function
248 name.
249
250
251 __-fno-strict-prototype__
252
253
254 Consider the declaration __int foo ();__. In C++, this
255 means that the function __foo__ takes no arguments. In
256 ANSI C, this is declared __int foo(void);__. With the
257 flag `__-fno-strict-prototype__', declaring functions
258 with no arguments is equivalent to declaring its argument
259 list to be untyped, i.e., __int foo ();__ is equivalent
260 to saying __int foo (...);__.
261
262
263 __-fnonnull-objects__
264
265
266 Normally, GNU C++ makes conservative assumptions about
267 objects reached through references. For example, the
268 compiler must check that `__a__' is not null in code like
269 the following:
270 obj
271 a.f (2);
272 Checking that references of this sort have non-null values
273 requires extra code, however, and it is unnecessary for many
274 programs. You can use `__-fnonnull-objects__' to omit the
275 checks for null, if your program doesn't require the default
276 checking.
277
278
279 __-fhandle-signatures__
280
281
282 __-fno-handle-signatures__
283
284
285 These options control the recognition of the
286 __signature__ and __sigof__ constructs for specifying
287 abstract types. By default, these constructs are not
288 recognized.
289
290
291 __-fthis-is-variable__
292
293
294 The incorporation of user-defined free store management into
295 C++ has made assignment to __this__ an anachronism.
296 Therefore, by default GNU C++ treats the type of __this__
297 in a member function of __class X__ to be __X
298 *const__. In other words, it is illegal to assign to
299 __this__ within a class member function. However, for
300 backwards compatibility, you can invoke the old behavior by
301 using `__-fthis-is-variable__'.
302
303
304 __-g__
305
306
307 Produce debugging information in the operating system's
308 native format (for DBX or SDB or DWARF). GDB also can work
309 with this debugging information. On most systems that use
310 DBX format, `__-g__' enables use of extra debugging
311 information that only GDB can use.
312
313
314 Unlike most other C compilers, GNU CC allows you to use
315 `__-g__' with `__-O__'. The shortcuts taken by
316 optimized code may occasionally produce surprising results:
317 some variables you declared may not exist at all; flow of
318 control may briefly move where you did not expect it; some
319 statements may not be executed because they compute constant
320 results or their values were already at hand; some
321 statements may execute in different places because they were
322 moved out of loops.
323
324
325 Nevertheless it proves possible to debug optimized output.
326 This makes it reasonable to use the optimizer for programs
327 that might have bugs.
328
329
330 __-I__''dir''
331
332
333 Append directory ''dir'' to the list of directories
334 searched for include files.
335
336
337 __-L__''dir''
338
339
340 Add directory ''dir'' to the list of directories to be
341 searched for `__-l__'.
342
343
344 __-l__''library''
345
346
347 Use the library named ''library'' when linking. (C++
348 programs often require `-lg++' for successful
349 linking.)
350
351
352 __-nostdinc__
353
354
355 Do not search the standard system directories for header
356 files. Only the directories you have specified with
357 __-I__ options (and the current directory, if
358 appropriate) are searched.
359
360
361 __-nostdinc++__
362
363
364 Do not search for header files in the standard directories
365 specific to C++, but do still search the other standard
366 directories. (This option is used when building
367 libg++.)
368
369
370 __-O__
371
372
373 Optimize. Optimizing compilation takes somewhat more time,
374 and a lot more memory for a large function.
375
376
377 __-o__ ''file''
378
379
380 Place output in file ''file''.
381
382
383 __-S__
384
385
386 Stop after the stage of compilation proper; do not assemble.
387 The output is an assembler code file for each non-assembler
388 input file specified.
389
390
391 __-traditional__
392
393
394 Attempt to support some aspects of traditional C
395 compilers.
396
397
398 Specifically, for both C and C++ programs:
399
400
401 In the preprocessor, comments convert to nothing at all,
402 rather than to a space. This allows traditional token
403 concatenation.
404
405
406 In the preprocessor, macro arguments are recognized within
407 string constants in a macro definition (and their values are
408 stringified, though without additional quote marks, when
409 they appear in such a context). The preprocessor always
410 considers a string constant to end at a
411 newline.
412
413
414 The preprocessor does not predefine the macro
415 ____STDC____ when you use `__-traditional__', but
416 still predefines____GNUC____ (since the GNU extensions
417 indicated by ____GNUC____ are not affected by
418 `__-traditional__'). If you need to write header files
419 that work differently depending on whether
420 `__-traditional__' is in use, by testing both of these
421 predefined macros you can distinguish four situations: GNU
422 C, traditional GNU C, other ANSI C compilers, and other old
423 C compilers.
424
425
426 String ``constants'' are not necessarily constant; they are
427 stored in writable space, and identical looking constants
428 are allocated separately.
429
430
431 For C++ programs only (not C), `__-traditional__' has one
432 additional effect: assignment to __this__ is permitted.
433 This is the same as the effect of
434 `__-fthis-is-variable__'.
435
436
437 __-U__''macro''
438
439
440 Undefine macro ''macro''.
441
442
443 __-Wall__
444
445
446 Issue warnings for conditions which pertain to usage that we
447 recommend avoiding and that we believe is easy to avoid,
448 even in conjunction with macros.
449
450
451 __-Wenum-clash__
452
453
454 Warn when converting between different enumeration
455 types.
456
457
458 __-Woverloaded-virtual__
459
460
461 In a derived class, the definitions of virtual functions
462 must match the type signature of a virtual function declared
463 in the base class. Use this option to request warnings when
464 a derived class declares a function that may be an erroneous
465 attempt to define a virtual function: that is, warn when a
466 function with the same name as a virtual function in the
467 base class, but with a type signature that doesn't match any
468 virtual functions from the base class.
469
470
471 __-Wtemplate-debugging__
472
473
474 When using templates in a C++ program, warn if debugging is
475 not yet fully available.
476
477
478 __-w__
479
480
481 Inhibit all warning messages.
482
483
484 __+e__''N''
485
486
487 Control how virtual function definitions are used, in a
488 fashion compatible with __cfront__ 1.x.
489 !!PRAGMAS
490
491
492 Two `__#pragma__' directives are supported for GNU C++,
493 to permit using the same header file for two purposes: as a
494 definition of interfaces to a given object class, and as the
495 full definition of the contents of that object
496 class.
497
498
499 __#pragma interface__
500
501
502 Use this directive in header files that define object
503 classes, to save space in most of the object files that use
504 those classes. Normally, local copies of certain information
505 (backup copies of inline member functions, debugging
506 information, and the internal tables that implement virtual
507 functions) must be kept in each object file that includes
508 class definitions. You can use this pragma to avoid such
509 duplication. When a header file containing `__#pragma
510 interface__' is included in a compilation, this auxiliary
511 information will not be generated (unless the main input
512 source file itself uses `__#pragma implementation__').
513 Instead, the object files will contain references to be
514 resolved at link time.
515
516
517 __#pragma implementation__
518
519
520 __#pragma implementation
521 __''objects''__.h__
522
523
524 Use this pragma in a main input file, when you want full
525 output from included header files to be generated (and made
526 globally visible). The included header file, in turn, should
527 use `__#pragma interface__'. Backup copies of inline
528 member functions, debugging information, and the internal
529 tables used to implement virtual functions are all generated
530 in implementation files.
531
532
533 If you use `__#pragma implementation__' with no argument,
534 it applies to an include file with the same basename as your
535 source file; for example, in `__allclass.cc__',
536 `__#pragma implementation__' by itself is equivalent to
537 `__#pragma implementation __'. Use
538 the string argument if you want a single implementation file
539 to include code from multiple header files.
540
541
542 There is no way to split up the contents of a single header
543 file into multiple implementation files.
544 !!FILES
545
546
547 file.h C header (preprocessor) file
548 file.i preprocessed C source file
549 file.C C++ source file
550 file.cc C++ source file
551 file.cxx C++ source file
552 file.s assembly language file
553 file.o object file
554 a.out link edited output''
555 TMPDIR''/cc temporary files''
556 LIBDIR''/cpp preprocessor''
557 LIBDIR''/cc1plus compiler''
558 LIBDIR''/collect linker front end needed on some
559 machines''
560 LIBDIR''/libgcc.a GCC subroutine library
561 /lib/crt[[01n].o start-up routine''
562 LIBDIR''/ccrt0 additional start-up routine for C++
563 /lib/libc.a standard C library, see intro(3)
564 /usr/include standard directory for __#include__
565 files''
566 LIBDIR''/include standard gcc directory for
567 __#include__ files''
568 LIBDIR''/g++-include additional g++ directory for
569 __#include__
570
571
572 ''LIBDIR'' is usually
573 __/usr/local/lib/__''machine''/''version''.''
574 TMPDIR'' comes from the environment variable __TMPDIR__
575 (default __/usr/tmp__ if available, else
576 __/tmp__).
577 !!SEE ALSO
578
579
580 gcc(1), cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1),
581 sdb(1).
582 `__gcc__', `__cpp__', `__as__',__`__ld__',__
583 and `__gdb__' entries in __info__.''
584 Using and Porting GNU CC (for version 2.0)'', Richard M.
585 Stallman; ''The C Preprocessor'', Richard M. Stallman;
586 ''Debugging with GDB: the GNU Source-Level Debugger'',
587 Richard M. Stallman and Roland H. Pesch; ''Using as: the
588 GNU Assembler'', Dean Elsner, Jay Fenlason
589 ''gld: the GNU linker'', Steve Chamberlain and Roland
590 Pesch.
591 !!BUGS
592
593
594 For instructions on how to report bugs, see the GCC
595 manual.
596 !!COPYING
597
598
599 Copyright (c) 1991, 1992, 1993 Free Software Foundation,
600 Inc.
601
602
603 Permission is granted to make and distribute verbatim copies
604 of this manual provided the copyright notice and this
605 permission notice are preserved on all copies.
606
607
608 Permission is granted to copy and distribute modified
609 versions of this manual under the conditions for verbatim
610 copying, provided that the entire resulting derived work is
611 distributed under the terms of a permission notice identical
612 to this one.
613
614
615 Permission is granted to copy and distribute translations of
616 this manual into another language, under the above
617 conditions for modified versions, except that this
618 permission notice may be included in translations approved
619 by the Free Software Foundation instead of in the original
620 English.
621 !!AUTHORS
622
623
624 See the GNU CC Manual for the contributors to GNU
625 CC.
626 ----
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