https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114872
--- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Dmitrii Pasechnik from comment #12) > A colleague disassembled, using ghidra (https://ghidra-sre.org/), the > results of the compilations with, respectively, -O2 and with -O0 flags. > Comparing the results, in the broken (built with -O2) case one sees a > miscompilation of a call to GAP_CallFunc3Args - it is called with one > argument less than it should, three instead of four! > > broken (-O2): > > > plVar9 = (long *)GAP_CallFunc3Args(*(undefined8 *)(param_1 + > > 0x20),local_a0[4], > > local_a8[4]); > > vs. good (-O0): > > < LAB_0013cbd9: > < plVar10 = (long *)GAP_CallFunc3Args(*(undefined8 *)(param_1 + > 0x20),local_a8[4], > < local_a0[4],plVar16[4]); > > And this is despite the prototype for calling GAP_CallFunc3Args() is > found in "gap/libgap-api.h", which is included in example.c as #include > "gap/libgap-api.h", meant to be respected during the compilation. > > I hope this helps in chasing down the obvious compiler bug. Perhaps it can > be also seen without disassembling, simply on the intermediate data > generated by the compiler. Both calls pass 4 arguments, both in optimized -O2 -fPIC GCC 13.2.1 dump and in assembly: movq -88(%rbp), %rdx movq %r12, %rcx movq %r13, %rsi movq %rax, %rdi call GAP_CallFunc3Args@PLT ... movq -88(%rbp), %rdx movq %r12, %rcx movq %r13, %rsi movq %rax, %rdi call GAP_CallFunc3Args@PLT and GAP_CallFunc3Args (_53, _47, __pyx_v_func_54(D), _49); ... _441 = GAP_CallFunc3Args (_98, _97, _96, _95);
