On Sun, 13 Jun 2010, Dave Korn wrote: > On 13/06/2010 20:55, Ian Lance Taylor wrote: > > David Brown <da...@westcontrol.com> writes: > > > >> If -flto were to activate the -fno-common flag, would that then catch > >> these potential problems with a linker error? > > > > We could perhaps do that for C/C++ code, but Fortran relies on common > > symbols. > > Well we shouldn't do it for plain C either, or at the very least should make > it depend on the -std= option in effect, but since the code is entirely valid > and legitimate C, I think we should acknowledge this is a weakness in our > compiler. The original testcase is a perfectly straightforward bit of C89; > there are two compatible tentative declarations of a variable of type int > called "v". We don't want to have to argue that one is in fact a variable of
This is not valid standard C; you can have two tentative definitions in the same translation unit, but not in different translation units. Allowing commons is listed as a common extension in C90 G.5.11. -- Joseph S. Myers jos...@codesourcery.com
