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2                        GCC Frequently Asked Questions
3
4   The   latest   version   of  this  document  is  always  available  at
5   [1]http://www.gnu.org/software/gcc/faq.html.
6
7   This  FAQ  tries  to  answer  specific  questions  concerning GCC. For
8   general  information  regarding C, C++, resp. Fortran please check the
9   [2]comp.lang.c   FAQ,   [3]comp.std.c++   FAQ,   and   the  [4]Fortran
10   Information page.
11
12   Other GCC-related FAQs: [5]libstdc++-v3, and [6]GCJ.
13     _________________________________________________________________
14
15                                   Questions
16
17    1. [7]General information
18         1. [8]What is the relationship between GCC and EGCS?
19         2. [9]What is the relationship between GCC and Cygnus / Red Hat?
20         3. [10]What is an open development model?
21         4. [11]How do I report a bug?
22         5. [12]How do I get a bug fixed or a feature added?
23         6. [13]Does GCC work on my platform?
24    2. [14]Installation
25         1. [15]How to install multiple versions of GCC
26         2. [16]Dynamic linker is unable to find GCC libraries
27         3. [17]libstdc++/libio tests fail badly with --enable-shared
28         4. [18]GCC can not find GNU as/GNU ld
29         5. [19]cpp: Usage:... Error
30         6. [20]Optimizing the compiler itself
31    3. [21]Testsuite problems
32         1. [22]Unable to run the testsuite
33         2. [23]How do I pass flags like -fnew-abi to the testsuite?
34         3. [24]How can I run the test suite with multiple options?
35    4. [25]Older versions of GCC
36         1. [26]Is there a stringstream / sstream for GCC 2.95.2?
37    5. [27]Miscellaneous
38         1. [28]Virtual memory exhausted
39         2. [29]Friend Templates
40         3. [30]dynamic_cast,   throw,  typeid  don't  work  with  shared
41            libraries
42         4. [31]Why do I need autoconf, bison, xgettext, automake, etc?
43         5. [32]Why can't I build a shared library?
44         6. [33]How   to   work   around   too  long  C++  symbol  names?
45            (-fsquangle)
46         7. [34]When  building  C++,  the  linker  says  my constructors,
47            destructors  or  virtual  tables are undefined, but I defined
48            them
49         8. [35]Will GCC someday include an incremental linker?
50     _________________________________________________________________
51
52                              General information
53
54What is the relationship between GCC and EGCS?
55
56   In  1990/1991  gcc version 1 had reached a point of stability. For the
57   targets  it could support, it worked well. It had limitations inherent
58   in  its  design  that would be difficult to resolve, so a major effort
59   was  made  to  resolve  those  limitiations  and gcc version 2 was the
60   result.
61
62   When  we  had  gcc2  in  a  useful  state, development efforts on gcc1
63   stopped  and we all concentrated on making gcc2 better than gcc1 could
64   ever  be.  This is the kind of step forward we wanted to make with the
65   EGCS project when it was formed in 1997.
66
67   In   April   1999  the  Free  Software  Foundation  officially  halted
68   development on the gcc2 compiler and appointed the EGCS project as the
69   official  GCC  maintainers.  The net result was a single project which
70   carries  forward  GCC  development  under  the ultimate control of the
71   [36]GCC Steering Committee.
72     _________________________________________________________________
73
74What is the relationship between GCC and Cygnus / Red Hat?
75
76   It  is  a  common  mis-conception  that  Red  Hat  controls GCC either
77   directly or indirectly.
78
79   While  Red  Hat  does  donate  hardware, network connections, code and
80   developer time to GCC development, Red Hat does not control GCC.
81
82   Overall  control  of  GCC  is  in  the  hands  of the [37]GCC Steering
83   Committee   which   includes   people  from  a  variety  of  different
84   organizations  and  backgrounds. The purpose of the steering committee
85   is  to  make  decisions in the best interest of GCC and to help ensure
86   that no individual or company has control over the project.
87
88   To  summarize,  Red  Hat  contributes to the GCC project, but does not
89   exert a controlling influence over GCC.
90     _________________________________________________________________
91
92What is an open development model?
93
94   We  are  using  a bazaar style [38][1] approach to GCC development: we
95   make  snapshots publicly available to anyone who wants to try them; we
96   welcome  anyone  to  join  the  development  mailing  list. All of the
97   discussions on the development mailing list are available via the web.
98   We're  going  to  be making releases with a much higher frequency than
99   they have been made in the past.
100
101   In  addition  to  weekly  snapshots of the GCC development sources, we
102   have  the sources readable from a CVS server by anyone. Furthermore we
103   are  using  remote CVS to allow remote maintainers write access to the
104   sources.
105
106   There  have  been  many  potential GCC developers who were not able to
107   participate  in  GCC  development in the past. We want these people to
108   help  in  any  way  they  can;  we  ultimately want GCC to be the best
109   compiler in the world.
110
111   A  compiler  is  a  complicated piece of software, there will still be
112   strong  central  maintainers  who will reject patches, who will demand
113   documentation  of  implementations,  and  who  will  keep the level of
114   quality  as high as it is today. Code that could use wider testing may
115   be integrated--code that is simply ill-conceived won't be.
116
117   GCC  is  not  the first piece of software to use this open development
118   process;  FreeBSD, the Emacs lisp repository, and the Linux kernel are
119   a few examples of the bazaar style of development.
120
121   With  GCC, we are adding new features and optimizations at a rate that
122   has  not  been  done  since  the  creation  of  gcc2;  these additions
123   inevitably  have  a temporarily destabilizing effect. With the help of
124   developers  working  together  with this bazaar style development, the
125   resulting  stability  and quality levels will be better than we've had
126   before.
127
128     [1]  We've  been discussing different development models a lot over
129     the past few months. The paper which started all of this introduced
130     two   terms:   A   cathedral  development  model  versus  a  bazaar
131     development  model.  The paper is written by Eric S. Raymond, it is
132     called  ``[39]The Cathedral and the Bazaar''. The paper is a useful
133     starting point for discussions.
134     _________________________________________________________________
135
136How do I report a bug?
137
138   There are complete instructions [40]here.
139     _________________________________________________________________
140
141How do I get a bug fixed or a feature added?
142
143   There  are  lots of ways to get something fixed. The list below may be
144   incomplete,  but  it covers many of the common cases. These are listed
145   roughly  in  order  of increasing difficulty for the average GCC user,
146   meaning  someone who is not skilled in the internals of GCC, and where
147   difficulty  is  measured in terms of the time required to fix the bug.
148   No  alternative  is  better  than any other; each has its benefits and
149   disadvantages.
150     * Hire  someone  to  fix it for you. There are various companies and
151       individuals  providing  support  for  GCC.  This alternative costs
152       money, but is relatively likely to get results.
153     * [41]Report  the  problem  to the GCC GNATS bug tracking system and
154       hope  that  someone  will  be kind enough to fix it for you. While
155       this  is  certainly  possible,  and  often  happens,  there  is no
156       guarantee  that  it  will. You should not expect the same response
157       from  this  method  that  you  would see from a commercial support
158       organization  since  the  people who read GCC bug reports, if they
159       choose  to  help  you,  will  be  volunteering  their  time.  This
160       alternative  will  work  best  if  you  follow  the  directions on
161       [42]submitting bugreports.
162     * Fix  it yourself. This alternative will probably bring results, if
163       you  work  hard enough, but will probably take a lot of time, and,
164       depending  on  the quality of your work and the perceived benefits
165       of  your  changes,  your  code may or may not ever make it into an
166       official release of GCC.
167     _________________________________________________________________
168
169Does GCC work on my platform?
170
171   The   host/target   specific   installation   notes  for  GCC  include
172   information  about  known  problems  with  installing  or using GCC on
173   particular  platforms. These are included in the sources for a release
174   in   INSTALL/specific.html,  and  the  [43]latest  version  is  always
175   available  at  the  GCC web site. Reports of [44]successful builds for
176   several versions of GCC are also available at the web site.
177     _________________________________________________________________
178
179                                 Installation
180
181How to install multiple versions of GCC
182
183   It  may  be  desirable to install multiple versions of the compiler on
184   the  same  system. This can be done by using different prefix paths at
185   configure time and a few symlinks.
186
187   Basically,   configure  the  two  compilers  with  different  --prefix
188   options,  then  build and install each compiler. Assume you want "gcc"
189   to be the latest compiler and available in /usr/local/bin; also assume
190   that  you want "gcc2" to be the older gcc2 compiler and also available
191   in /usr/local/bin.
192
193   The  easiest  way  to  do  this  is  to  configure  the  new  GCC with
194   --prefix=/usr/local/gcc      and      the      older     gcc2     with
195   --prefix=/usr/local/gcc2.  Build and install both compilers. Then make
196   a  symlink  from /usr/local/bin/gcc to /usr/local/gcc/bin/gcc and from
197   /usr/local/bin/gcc2  to  /usr/local/gcc2/bin/gcc. Create similar links
198   for the "g++", "c++" and "g77" compiler drivers.
199
200   An   alternative   to   using   symlinks   is   to  configure  with  a
201   --program-transform-name  option.  This option specifies a sed command
202   to  process  installed  program  names  with.  Using  it  you can, for
203   instance, have all the new GCC programs installed as "new-gcc" and the
204   like.  You  will  still have to specify different --prefix options for
205   new  GCC  and old GCC, because it is only the executable program names
206   that are transformed. The difference is that you (as administrator) do
207   not  have  to set up symlinks, but must specify additional directories
208   in your (as a user) PATH. A complication with --program-transform-name
209   is  that the sed command invariably contains characters significant to
210   the  shell,  and  these  have  to be escaped correctly, also it is not
211   possible  to  use  "^"  or  "$"  in the command. Here is the option to
212   prefix "new-" to the new GCC installed programs:
213
214     --program-transform-name='s,\\\\(.*\\\\),new-\\\\1,'
215
216   With the above --prefix option, that will install the new GCC programs
217   into  /usr/local/gcc/bin  with  names  prefixed by "new-". You can use
218   --program-transform-name  if  you  have  multiple versions of GCC, and
219   wish to be sure about which version you are invoking.
220
221   If  you use --prefix, GCC may have difficulty locating a GNU assembler
222   or  linker on your system, [45]GCC can not find GNU as/GNU ld explains
223   how to deal with this.
224
225   Another  option  that may be easier is to use the --program-prefix= or
226   --program-suffix=  options  to  configure. So if you're installing GCC
227   2.95.2  and  don't  want  to  disturb  the  current  version of GCC in
228   /usr/local/bin/, you could do
229
230     configure --program-suffix=-2.95.2 <other configure options>
231
232   This should result in GCC being installed as /usr/local/bin/gcc-2.95.2
233   instead of /usr/local/bin/gcc.
234     _________________________________________________________________
235
236Dynamic linker is unable to find GCC libraries
237
238   This problem manifests itself by programs not finding shared libraries
239   they  depend on when the programs are started. Note this problem often
240   manifests  itself  with  failures  in  the libio/libstdc++ tests after
241   configuring with --enable-shared and building GCC.
242
243   GCC  does  not  specify  a runpath so that the dynamic linker can find
244   dynamic libraries at runtime.
245
246   The  short  explanation  is that if you always pass a -R option to the
247   linker,  then  your programs become dependent on directories which may
248   be NFS mounted, and programs may hang unnecessarily when an NFS server
249   goes down.
250
251   The  problem  is  not  programs that do require the directories; those
252   programs  are  going  to  hang  no  matter what you do. The problem is
253   programs that do not require the directories.
254
255   SunOS  effectively always passed a -R option for every -L option; this
256   was  a  bad  idea,  and  so  it was removed for Solaris. We should not
257   recreate it.
258
259   However,  if  you  feel  you  really  need such an option to be passed
260   automatically  to  the  linker,  you may add it to the GCC specs file.
261   This  file  can  be found in the same directory that contains cc1 (run
262   gcc -print-prog-name=cc1 to find it). You may add linker flags such as
263   -R  or  -rpath, depending on platform and linker, to the *link or *lib
264   specs.
265
266   Another  alternative is to install a wrapper script around gcc, g++ or
267   ld  that  adds  the  appropriate directory to the environment variable
268   LD_RUN_PATH or equivalent (again, it's platform-dependent).
269
270   Yet another option, that works on a few platforms, is to hard-code the
271   full  pathname  of  the  library  into  its  soname.  This can only be
272   accomplished   by   modifying   the   appropriate   .ml   file  within
273   libstdc++/config (and also libg++/config, if you are building libg++),
274   so  that $(libdir)/ appears just before the library name in -soname or
275   -h options.
276     _________________________________________________________________
277
278GCC can not find GNU as/GNU ld
279
280   GCC  searches the PATH for an assembler and a loader, but it only does
281   so after searching a directory list hard-coded in the GCC executables.
282   Since,  on most platforms, the hard-coded list includes directories in
283   which  the  system  asembler  and loader can be found, you may have to
284   take  one  of  the  following actions to arrange that GCC uses the GNU
285   versions of those programs.
286
287   To ensure that GCC finds the GNU assembler (the GNU loader), which are
288   required  by  [46]some configurations, you should configure these with
289   the same --prefix option as you used for GCC. Then build & install GNU
290   as (GNU ld) and proceed with building GCC.
291
292   Another  alternative is to create links to GNU as and ld in any of the
293   directories  printed  by  the  command  `gcc -print-search-dirs | grep
294   '^programs:''.  The  link  to  `ld'  should be named `real-ld' if `ld'
295   already exists. If such links do not exist while you're compiling GCC,
296   you  may  have to create them in the build directories too, within the
297   gcc directory and in all the gcc/stage* subdirectories.
298
299   GCC  2.95 allows you to specify the full pathname of the assembler and
300   the linker to use. The configure flags are `--with-as=/path/to/as' and
301   `--with-ld=/path/to/ld'.  GCC  will  try to use these pathnames before
302   looking  for  `as'  or `(real-)ld' in the standard search dirs. If, at
303   configure-time,  the specified programs are found to be GNU utilities,
304   `--with-gnu-as' and `--with-gnu-ld' need not be used; these flags will
305   be  auto-detected.  One drawback of this option is that it won't allow
306   you  to  override  the  search  path  for  assembler  and  linker with
307   command-line options -B/path/ if the specified filenames exist.
308     _________________________________________________________________
309
310cpp: Usage:... Error
311
312   If  you  get  an  error like this when building GCC (particularly when
313   building   __mulsi3),  then  you  likely  have  a  problem  with  your
314   environment variables.
315  cpp: Usage: /usr/lib/gcc-lib/i586-unknown-linux-gnulibc1/2.7.2.3/cpp
316  [switches] input output
317
318   First   look   for   an   explicit   '.'  in  either  LIBRARY_PATH  or
319   GCC_EXEC_PREFIX  from your environment. If you do not find an explicit
320   '.',  look  for an empty pathname in those variables. Note that ':' at
321   either the start or end of these variables is an implicit '.' and will
322   cause problems.
323
324   Also note '::' in these paths will also cause similar problems.
325     _________________________________________________________________
326
327Optimizing the compiler itself
328
329   If  you  want to test a particular optimization option, it's useful to
330   try  bootstrapping  the  compiler  with  that  option  turned  on. For
331   example, to test the -fssa option, you could bootstrap like this:
332make BOOT_CFLAGS="-O2 -fssa" bootstrap
333     _________________________________________________________________
334
335                              Testsuite problems
336
337Unable to run the testsuite
338
339   If  you  get a message about unable to find "standard.exp" when trying
340   to run the GCC testsuites, then your dejagnu is too old to run the GCC
341   tests.  You  will  need  to  get  a  newer  version  of  dejagnu  from
342   [47]http://www.gnu.org/software/dejagnu/dejagnu.html.
343     _________________________________________________________________
344
345How do I pass flags like -fnew-abi to the testsuite?
346
347   If  you  invoke  runtest directly, you can use the --tool_opts option,
348   e.g:
349  runtest --tool_opts "-fnew-abi -fno-honor-std" <other options>
350
351   Or,  if you use make check you can use the make variable RUNTESTFLAGS,
352   e.g:
353  make RUNTESTFLAGS="--tool_opts '-fnew-abi -fno-honor-std'" check-g++
354     _________________________________________________________________
355
356How can I run the test suite with multiple options?
357
358   If you invoke runtest directly, you can use the --target_board option,
359   e.g:
360  runtest --target_board "unix{-fPIC,-fpic,}" <other options>
361
362   Or,  if you use make check you can use the make variable RUNTESTFLAGS,
363   e.g:
364  make RUNTESTFLAGS="--target_board 'unix{-fPIC,-fpic,}'" check-gcc
365
366   Either  of  these  examples  will run the tests three times. Once with
367   -fPIC, once with -fpic, and once with no additional flags.
368
369   This technique is particularly useful on multilibbed targets.
370     _________________________________________________________________
371
372                        Older versions of GCC and EGCS
373
374Is there a stringstream / sstream for GCC 2.95.2?
375
376   Yes, it's at:
377   [48]http://gcc.gnu.org/ml/libstdc++/2000-q2/msg00700/sstream.
378     _________________________________________________________________
379
380                                 Miscellaneous
381
382Virtual memory exhausted error
383
384   This  error  means  your system ran out of memory; this can happen for
385   large  files,  particularly  when  optimizing.  If you're getting this
386   error  you  should  consider trying to simplify your files or reducing
387   the optimization level.
388
389   Note  that  using -pedantic or -Wreturn-type can cause an explosion in
390   the  amount of memory needed for template-heavy C++ code, such as code
391   that  uses STL. Also note that -Wall includes -Wreturn-type, so if you
392   use -Wall you will need to specify -Wno-return-type to turn it off.
393     _________________________________________________________________
394
395Friend Templates
396
397   In order to make a specialization of a template function a friend of a
398   (possibly  template)  class, you must explicitly state that the friend
399   function  is  a template, by appending angle brackets to its name, and
400   this  template  function  must  have  been declared already. Here's an
401   example:
402template <typename T> class foo {
403  friend void bar(foo<T>);
404}
405
406   The  above  declaration declares a non-template function named bar, so
407   it  must  be  explicitly  defined  for  each  specialization of foo. A
408   template  definition of bar won't do, because it is unrelated with the
409   non-template declaration above. So you'd have to end up writing:
410void bar(foo<int>) { /* ... */ }
411void bar(foo<void>) { /* ... */ }
412
413   If  you  meant  bar  to  be  a  template  function,  you  should  have
414   forward-declared it as follows. Note that, since the template function
415   declaration  refers  to the template class, the template class must be
416   forward-declared too:
417template <typename T>
418class foo;
419
420template <typename T>
421void bar(foo<T>);
422
423template <typename T>
424class foo {
425  friend void bar<>(foo<T>);
426};
427
428template <typename T>
429void bar(foo<T>) { /* ... */ }
430
431   In  this case, the template argument list could be left empty, because
432   it  can  be  implicitly  deduced  from the function arguments, but the
433   angle  brackets  must  be  present,  otherwise the declaration will be
434   taken  as a non-template function. Furthermore, in some cases, you may
435   have   to   explicitly  specify  the  template  arguments,  to  remove
436   ambiguity.
437
438   An error in the last public comment draft of the ANSI/ISO C++ Standard
439   and  the  fact  that previous releases of GCC would accept such friend
440   declarations  as  template declarations has led people to believe that
441   the forward declaration was not necessary, but, according to the final
442   version of the Standard, it is.
443     _________________________________________________________________
444
445dynamic_cast, throw, typeid don't work with shared libraries
446
447   The new C++ ABI in the GCC 3.0 series uses address comparisons, rather
448   than string compares, to determine type equality. This leads to better
449   performance.  Like  other objects that have to be present in the final
450   executable,  these  std::typeinfo_t  objects have what is called vague
451   linkage  because  they  are  not  tightly  bound to any one particular
452   translation  unit  (object file). The compiler has to emit them in any
453   translation  unit  that  requires their presence, and then rely on the
454   linking  and  loading  process  to  make sure that only one of them is
455   active  in  the  final  executable.  With  static linking all of these
456   symbols  are  resolved at link time, but with dynamic linking, further
457   resolution occurs at load time. You have to ensure that objects within
458   a  shared  library  are resolved against objects in the executable and
459   other shared libraries.
460     * For  a  program  which  is  linked  against  a  shared library, no
461       additional precautions need taking.
462     * You  cannot  create a shared library with the "-Bsymbolic" option,
463       as that prevents the resolution described above.
464     * If  you  use dlopen to explicitly load code from a shared library,
465       you  must do several things. First, export global symbols from the
466       executable  by  linking  it  with  the "-E" flag (you will have to
467       specify  this  as  "-Wl,-E"  if you are invoking the linker in the
468       usual  manner  from  the compiler driver, g++). You must also make
469       the   external   symbols  in  the  loaded  library  available  for
470       subsequent  libraries by providing the RTLD_GLOBAL flag to dlopen.
471       The symbol resolution can be immediate or lazy.
472
473   Template  instantiations  are  another,  user visible, case of objects
474   with vague linkage, which needs similar resolution. If you do not take
475   the  above precautions, you may discover that a template instantiation
476   with  the same argument list, but instantiated in multiple translation
477   units,  has several addresses, depending in which translation unit the
478   address  is  taken.  (This  is  not  an exhaustive list of the kind of
479   objects  which  have  vague  linkage  and  are expected to be resolved
480   during linking & loading.)
481
482   If  you  are  worried  about  different  objects  with  the  same name
483   colliding  during  the linking or loading process, then you should use
484   namespaces  to  disambiguate them. Giving distinct objects with global
485   linkage  the same name is a violation of the One Definition Rule (ODR)
486   [basic.def.odr].
487
488   For more details about the way that GCC implements these and other C++
489   features,   please   read   the   [49]ABI   specification.   Note  the
490   std::typeinfo_t  objects which must be resolved all begin with "_ZTS".
491   Refer   to  ld's  documentation  for  a  description  of  the  "-E"  &
492   "-Bsymbolic" flags.
493     _________________________________________________________________
494
495Why do I need autoconf, bison, xgettext, automake, etc?
496
497   If  you're  using  diffs up dated from one snapshot to the next, or if
498   you're  using  the  CVS  repository,  you  may need several additional
499   programs to build GCC.
500
501   These  include, but are not necessarily limited to autoconf, automake,
502   bison, and xgettext.
503
504   This  is  necessary  because  neither  diff  nor  cvs  keep timestamps
505   correct.  This causes problems for generated files as "make" may think
506   those generated files are out of date and try to regenerate them.
507
508   An  easy  way  to  work  around  this problem is to use the gcc_update
509   script  in  the  contrib  subdirectory  of  GCC,  which  handles  this
510   transparently  without requiring installation of any additional tools.
511   (Note: Up to and including GCC 2.95 this script was called egcs_update
512   .)
513
514   When  building  from diffs or CVS or if you modified some sources, you
515   may also need to obtain development versions of some GNU tools, as the
516   production  versions  do not necessarily handle all features needed to
517   rebuild GCC.
518
519   In    general,    the   current   versions   of   these   tools   from
520   [50]ftp://ftp.gnu.org/gnu/ will work. At present, Autoconf 2.50 is not
521   supported, and you will need to use Autoconf 2.13; work is in progress
522   to fix this problem. Also look at
523   [51]ftp://gcc.gnu.org/pub/gcc/infrastructure/ for any special versions
524   of packages.
525     _________________________________________________________________
526
527Why can't I build a shared library?
528
529   When  building  a shared library you may get an error message from the
530   linker like `assert pure-text failed:' or `DP relative code in file'.
531
532   This  kind  of error occurs when you've failed to provide proper flags
533   to gcc when linking the shared library.
534
535   You can get this error even if all the .o files for the shared library
536   were  compiled  with  the  proper  PIC  option. When building a shared
537   library,  gcc  will  compile  additional  code  to  be included in the
538   library.  That  additional  code must also be compiled with the proper
539   PIC option.
540
541   Adding  the  proper PIC option (-fpic or -fPIC) to the link line which
542   creates  the  shared  library  will  fix  this problem on targets that
543   support PIC in this manner. For example:
544        gcc -c -fPIC myfile.c
545        gcc -shared -o libmyfile.so -fPIC myfile.o
546     _________________________________________________________________
547
548How to work around too long C++ symbol names (-fsquangle)
549
550   This  question does not apply to GCC 3.0 or later versions, which have
551   a new C++ ABI with much shorter mangled names.
552
553   If  the  standard assembler of your platform can't cope with the large
554   symbol  names  that  the default g++ name mangling mechanism produces,
555   your best bet is to use GNU as, from the GNU binutils package.
556
557   Unfortunately, GNU as does not support all platforms supported by GCC,
558   so  you  may  have  to use an experimental work-around: the -fsquangle
559   option, that enables compression of symbol names.
560
561   Note  that  this  option  is  still  under development, and subject to
562   change.  Since it modifies the name mangling mechanism, you'll need to
563   build  libstdc++ and any other C++ libraries with this option enabled.
564   Furthermore, if this option changes its behavior in the future, you'll
565   have to rebuild them all again. :-(
566
567   This    option   can   be   enabled   by   default   by   initializing
568   `flag_do_squangling'   with   `1'   in  `gcc/cp/decl2.c'  (it  is  not
569   initialized by default), then rebuilding GCC and any C++ libraries.
570     _________________________________________________________________
571
572When building C++, the linker says my constructors, destructors or virtual
573tables are undefined, but I defined them
574
575   The  ISO  C++  Standard  specifies that all virtual methods of a class
576   that  are  not  pure-virtual must be defined, but does not require any
577   diagnostic  for  violations  of  this rule [class.virtual]/8. Based on
578   this   assumption,   GCC   will   only  emit  the  implicitly  defined
579   constructors,  the assignment operator, the destructor and the virtual
580   table  of  a class in the translation unit that defines its first such
581   non-inline method.
582
583   Therefore,  if  you  fail to define this particular method, the linker
584   may  complain  about  the lack of definitions for apparently unrelated
585   symbols.  Unfortunately,  in  order  to improve this error message, it
586   might  be  necessary  to  change  the linker, and this can't always be
587   done.
588
589   The  solution  is to ensure that all virtual methods that are not pure
590   are  defined.  Note  that  a  destructor must be defined even if it is
591   declared pure-virtual [class.dtor]/7.
592     _________________________________________________________________
593
594Will GCC someday include an incremental linker?
595
596   Incremental  linking is part of the linker, not the compiler. As such,
597   GCC doesn't have anything to do with incremental linking. Depending on
598   what  platform  you  use,  it  may  be possible to tell GCC to use the
599   platform's native linker (e.g., Solaris' ild(1)).
600
601References
602
603   1. http://www.gnu.org/software/gcc/faq.html
604   2. http://www.eskimo.com/~scs/C-faq/top.html
605   3. http://www.research.att.com/~austern/csc/faq.html
606   4. http://www.fortran.com/fortran/info.html
607   5. http://gcc.gnu.org/onlinedocs/libstdc++/faq/index.html
608   6. http://gcc.gnu.org/java/faq.html
609   7. http://gcc.gnu.org/faq.html#general
610   8. http://gcc.gnu.org/faq.html#gcc
611   9. http://gcc.gnu.org/faq.html#cygnus
612  10. http://gcc.gnu.org/faq.html#open-development
613  11. http://gcc.gnu.org/faq.html#bugreport
614  12. http://gcc.gnu.org/faq.html#support
615  13. http://gcc.gnu.org/faq.html#platforms
616  14. http://gcc.gnu.org/faq.html#installation
617  15. http://gcc.gnu.org/faq.html#multiple
618  16. http://gcc.gnu.org/faq.html#rpath
619  17. http://gcc.gnu.org/faq.html#rpath
620  18. http://gcc.gnu.org/faq.html#gas
621  19. http://gcc.gnu.org/faq.html#environ
622  20. http://gcc.gnu.org/faq.html#optimizing
623  21. http://gcc.gnu.org/faq.html#testsuite
624  22. http://gcc.gnu.org/faq.html#dejagnu
625  23. http://gcc.gnu.org/faq.html#testoptions
626  24. http://gcc.gnu.org/faq.html#multipletests
627  25. http://gcc.gnu.org/faq.html#old
628  26. http://gcc.gnu.org/faq.html#2.95sstream
629  27. http://gcc.gnu.org/faq.html#misc
630  28. http://gcc.gnu.org/faq.html#memexhausted
631  29. http://gcc.gnu.org/faq.html#friend
632  30. http://gcc.gnu.org/faq.html#dso
633  31. http://gcc.gnu.org/faq.html#generated_files
634  32. http://gcc.gnu.org/faq.html#picflag-needed
635  33. http://gcc.gnu.org/faq.html#squangle
636  34. http://gcc.gnu.org/faq.html#vtables
637  35. http://gcc.gnu.org/faq.html#incremental
638  36. http://gcc.gnu.org/steering.html
639  37. http://gcc.gnu.org/steering.html
640  38. http://gcc.gnu.org/faq.html#cathedral-vs-bazaar
641  39. http://www.tuxedo.org/~esr/writings/cathedral-bazaar/
642  40. http://gcc.gnu.org/bugs.html
643  41. http://gcc.gnu.org/bugs.html
644  42. http://gcc.gnu.org/bugs.html
645  43. http://gcc.gnu.org/install/specific.html
646  44. http://gcc.gnu.org/buildstat.html
647  45. http://gcc.gnu.org/faq.html#gas
648  46. http://gcc.gnu.org/install/specific.html
649  47. http://www.gnu.org/software/dejagnu/dejagnu.html
650  48. http://gcc.gnu.org/ml/libstdc++/2000-q2/msg00700/sstream
651  49. http://www.codesourcery.com/cxx-abi/
652  50. ftp://ftp.gnu.org/gnu/
653  51. ftp://gcc.gnu.org/pub/gcc/infrastructure/
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