https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80038
--- Comment #17 from Xi Ruoyao <ryxi at stu dot xidian.edu.cn> --- A simple test case for bisecting: extern "C" { int x(); int y(int); int z(); } int z() { int ret = _Cilk_spawn y(x()); return ret; } Compile with '-fcilkplus -S'. According to cilkplus spec, x() should be evaluated in the child (for the asm produced by GCC, in _cilk_spn_0). If you find "call x" in the asm of "z" instead of "_cilk_spn_0", that version of GCC is buggy.