https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46476
--- Comment #25 from Richard Biener <rguenth at gcc dot gnu.org> --- Created attachment 51878 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51878&action=edit -Wunreachable-code-return at GIMPLE lowering time This is an alternative change only implementing -Wunreachable-code-return (-Wunreachable-code-throw should be doable within this framework as well). It does so during GIMPLE lowering where we still have return stmts using the can_fallthru logic already present. The approach has the same issues with premature optimization by the C++ frontend eliding if (0) and if (1) as shown during bootstrap so the relevant hunk is included here, too, likewise the double return in main(). It also warns for void baz(); void foo (int b) { if (b) __builtin_abort (); else return; baz (); } but not for void baz(); void foo (int b) { if (b) return; else __builtin_abort (); baz (); } as the previous stmt here is not the return but the abort() but in both cases baz () is not really "after return" but after an if, but that part of the IL structure is not easily visible. For the same reason implementing -Wunreachable-code-break as supported by clang is difficult (break is just a goto in GIMPLE). At least this patch passes bootstrap and would have found one real issue but not the problematic dead "looping" stmts.
