https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62063
--- Comment #2 from Ferenc Géczi <ferenc.geczi at ericsson dot com> --- (In reply to Jonathan Wakely from comment #1) > (In reply to Ferenc Géczi from comment #0) > > Created attachment 33276 [details] > > Source code for reproducing the reported issue > > > > g++ disregards that template specialization might happen in a different > > compilation unit. > > How is the compiler supposed to know that? > > If you don't declare a specialization before it would be needed the compiler > will not use it, and the program has undefined behaviour. > > > For comparison, clang++ works as expected with -O0, without the > > -fnon-callexceptions. > > Although it has the same the behavior with higher optimization levels. > > That should tell you your expectation is wrong. Indeed. (In reply to Jonathan Wakely from comment #1) > (In reply to Ferenc Géczi from comment #0) > > Created attachment 33276 [details] > > Source code for reproducing the reported issue > > > > g++ disregards that template specialization might happen in a different > > compilation unit. > > How is the compiler supposed to know that? > > If you don't declare a specialization before it would be needed the compiler > will not use it, and the program has undefined behaviour. > > > For comparison, clang++ works as expected with -O0, without the > > -fnon-callexceptions. > > Although it has the same the behavior with higher optimization levels. > > That should tell you your expectation is wrong. Thank you for the quick reply, and I apologize for the false alarm. Now I found it in the standard. You are absolutely right.
