https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95677
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to liusujian from comment #2) > (In reply to Richard Biener from comment #1) > > It's more likely the GENERIC / cgraph output by the C++ frontend is not > > correct > > and works by accident without LTO. Initial symbol table: > > > > Initial Symbol table: > > > > int {anonymous}::xx/3 (int {anonymous}::xx) @0x7f615d2d8180 > > Type: variable > > Visibility: external > > References: > > Referring: _ZN12_GLOBAL__N_13fooEv/0 (write) > > Availability: not-ready > > Varpool flags: > > main/2 (int main()) @0x7f615d421168 > > Type: function definition analyzed > > Visibility: force_output no_reorder public > > Aux: @0x37a5000 > > References: int {anonymous}::xx/1 (write) > > Referring: > > Function flags: body > > Called by: > > Calls: > > int {anonymous}::xx/1 (int {anonymous}::xx) @0x7f615d2d8100 > > Type: variable definition analyzed > > Visibility: force_output no_reorder > > Aux: @0x7f615d421168 > > References: > > Referring: main/2 (write) > > Availability: not-ready > > Varpool flags: initialized > > _ZN12_GLOBAL__N_13fooEv/0 (void {anonymous}::foo()) @0x7f615d421000 > > Type: function definition analyzed > > Visibility: force_output no_reorder > > Aux: @0x7f615d2d8100 > > References: int {anonymous}::xx/3 (write) > > Referring: > > Function flags: body > > Called by: > > Calls: > > > > where you can see there are actually two 'xx' objects and the C++ FE > > takes it up to the linker/assembler to resolve them. But the symtab > > code does not include such "resolving" step. > > > In other words, C++ is currently unable to deal with this scenario ? Or any > other problems cause the error? The C++ frontend creates two distinct objects for 'xx' (thus it does not know they refer to the same object). Not sure if it is possible to exploit this fact to create a testcase that shows this fact even without LTO. I guess using constexpr and fail to constexpr evaluate a function using constexpr 'xx'? Not sure if there can be a "extern" constexpr though ;) As said the testcase "works" without LTO because both instances mangle to the same symbol name so the assembler/linker figure they _are_ the same object. Just the C++ frontend doesn't know within this TU.