https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68771
--- Comment #13 from Iain Sandoe <iains at gcc dot gnu.org> --- (In reply to Iain Sandoe from comment #12) > (In reply to Daniel Vollmer from comment #10) > > Created attachment 46036 [details] > > Example triggering "This was likely caused by different translation units > > being compiled with different visibility settings." > > > > Generates (w/ g++-7.4 on Darwin) > > > > ld: warning: direct access in function '__GLOBAL__sub_I_65535_0_test.cpp' > > from file > > '/var/folders/02/yl3m8d4d0397mk6dxn6dpcqw0000gp/T//ccuYv6qu.ltrans0.ltrans. > > o' to global weak symbol '__ZGVZ19BroadcastFromMasterImEvPT_mE4bufs' from > > file > > '/var/folders/02/yl3m8d4d0397mk6dxn6dpcqw0000gp/T//ccuYv6qu.ltrans0.ltrans. > > o' means the weak symbol cannot be overridden at runtime. This was likely > > caused by different translation units being compiled with different > > visibility settings. > > Thanks, I can reproduce this with my local gcc-7 branch, > interesting that it needs both -Ofast and -fprofile-generate to fire. OK (initial analysis). what we have is __ZGVZ19BroadcastFromMasterImEvPT_mE4bufs: .space 8 .... LPX0: .... and then a reference to LPX0 in __GLOBAL__sub_I_65535_0_test.cpp. So ld64 breaks the code and data into "atoms" where each atom begins with a linker-visible symbol. What it's saying is that the data pointed to by LPX0 is in the atom named __ZGVZ19BroadcastFromMasterImEvPT_mE4bufs (because LPX0 is not visible to the linker). right now, not sure if it's really a potential issue or just more linker warning noise - need to look at it fresh with plenty of coffee. FWIW, Linux generates pretty much identical code, but (of course) the BFD linker has different behaviour from Darwin's ld64. ===== So, we now have two different issues, neither of which is related to the current bug title :) Please pick one - and make a new PR for the second (probably ^^^^ this stuff is quite self-contained and could be split out) ... we can then retitle the existing bug to make it easier for folks to find things.
