Re: c++/6771: no code emitted for locally unused class with dllexport attribute

["Raoul Gough" <RaoulGough at yahoo dot co dot uk>]

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&p
r=6771

I have some more information regarding this dllexport problem (and
a quick and dirty fix for my system). I hope this is the right way to
submit additional information...

I've determined that the problematic member function (foofunction) is
having comdat_flag set (I believe erroneously) in decl2.c via the
import_export_decl function (called from finish_file in the first
deferred_fns loop). According the the comments in tree.h, comdat_flag
should be set for entities "guaranteed to be generated by any
translation unit that needs them, and therefore need not be put out
anywhere where they are not needed", which is clearly not the case
here (member function of a class with attribute dllexport). So I just
hacked the comdat_linkage function as follows, and the problem went
away :-)

/cygdrive/d/gcc/CVS/gcc/gcc/cp $ diff decl2.c~ decl2.c
2183c2183
<   if (DECL_LANG_SPECIFIC (decl))
---
>   if (DECL_LANG_SPECIFIC (decl) && !i386_pe_dllexport_p (decl))

(diff with decl2.c CVS:1.520.2.5)

This generates an "implicit declaration" warning, and is only suitable
for systems that use config/i386/winnt.c. I'm sure this is not the
right way to fix it, because comdat_linkage should probably never get
called on a dllexport'd member function - maybe a better fix would be
to clear DECL_DECLARED_INLINE_P at some stage?

I'm willing to spend some more time on this (and possibly any other
open bugs within my abilities), but would need a bit of advice on
producing a legitimate fix.

Regards,
Raoul Gough.


PS: I've upgraded via CVS to gcc_latest_snapshot (gcc_ss_20020521) and
the problem is unchanged. Also, setting the -fno-default-inline flag
fixes the problem for the export case, but crashes the compiler for
the import case:

/cygdrive/f/Users/Raoul/cxx $ /usr/local/bin/g++ -c
dllexport.cc -fno-default-inline -save-temps
dllexport.cc: In member function `void bar::barfunction()':
dllexport.cc:26: Internal compiler error in rest_of_compilation, at
toplev.c:
   3478
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.

This would otherwise be a temporary work-around for the original problem.



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