------- Comment #8 from dave at hiauly1 dot hia dot nrc dot ca 2006-12-04 01:29 ------- Subject: Re: Shared libstdc++ fails to link
> > > This problem was introduced by this change: > > That makes less sense really, because this just changes how to deal with > > TREE_NOTHROW. This sounds like a latent bug really. > > The change does affect the EH table (diff attached). Hacking the > assembler output for stdexcept, I find that it's the following > reference that causes the error: > > .word L$FB0940 The TREE_NOTHROW change exposes a problem in HP ld that only can be fixed by HP and that's not going to happen. The TREE_NOTHROW change has been applied to 4.1, so we have a regression. However, it probably would be possible to trigger this problem even without the TREE_NOTHROW change (e.g., setting flag_non_call_exceptions). So, I think the only fix is to revert DWARF2 EH support on this target on 4.1 and later ;) I've debugged HP ld sufficiently to determine the nature of the problem. Weak symbol support is implemented on this target using "COMDAT" subspaces. When duplicates occur in a link, the HP linker nullifies symbol references to the second and latter occurences of symbols in the "COMDAT" subspace. It does this by changing the symbol type to ST_NULL. As a result, the references to omitted subspaces change from ST_DATA to ST_NULL. This triggers the DATA_ONE_SYM_FOR_PLAB error from HP ld when we hit a reference in the DWARF2 EH table to an omitted subspace. The message is actually somewhat misleading as we nominally started with a ST_DATA symbol and not a ST_CODE code symbol. Well, actually the symbol is a code symbol but the default is to treat code labels as data symbols! I tried changing the absolute reference to a plabel reference but this results in another problem. Attached is a simplified bit of assembler output from stdexcept.cc and a small hack to HP ld which might work around the problem. To trigger the problem, the assembled output from pr29487.s needs to included twice in a shared link. Dave ------- Comment #9 from dave at hiauly1 dot hia dot nrc dot ca 2006-12-04 01:29 ------- Created an attachment (id=12737) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12737&action=view) ------- Comment #10 from dave at hiauly1 dot hia dot nrc dot ca 2006-12-04 01:29 ------- Created an attachment (id=12738) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12738&action=view) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29487
