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
type "int compiled with LTO" in order to back-justify some argument that they
are not the same and this example violates some (vague and not
standard-specified) C equivalent of the ODR.
cheers,
DaveK
