https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41227
--- Comment #19 from rguenther at suse dot de <rguenther at suse dot de> --- On Mon, 14 Jul 2014, burnus at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41227 > > --- Comment #17 from Tobias Burnus <burnus at gcc dot gnu.org> --- > (In reply to Francois-Xavier Coudert from comment #12) > > I disagree with Tobias' reading: it seems to me that the single-variable > > common block should be interoperable with both the single-common C struct > > and C variable. > > Well, Bill Long of Cray seems to agree with my interpretation, cf. > http://mailman.j3-fortran.org/pipermail/j3/2010-February/003358.html But that answer suggests we get it wrong (currenty interoperating with the C struct { int i; } works and with the plain decl it doesn't). The answer specifically doesn't say that only (1) is valid. > > The Intel compiler makes both cases work: > > Well, it also works with gfortran - the question is only whether it works by > chance or by purpose. If it works by chance and is invalid LTO is not required > to support it. Currently it works "by chance" because without LTO the compiler doesn't see both sides. With LTO it notices there is an inconsistency that with a clever testcase will result in wrong code (make a fortran subroutine that assigns sth to the variable, call it from the C main after its assignment of 42, read the var again in main and see it optimized to '42' in case the fortran function call is inlined)
