On Thu, Jul 25, 2013 at 10:40:22PM +0000, Joseph S. Myers wrote: > What happens if you bootstrap with this enabled - do whatever failures > appear look like genuine bugs? Running the testsuite with a compiler > built with this option? Running the testsuite with this option used when > compiling all these tests. I guess that initially a bootstrap with this > option may fail because of existing bugs, and so the other tests mentioned > can't yet be run - but using this option on GCC itself, and making sure > that as far as possible it doesn't break compiling things or change > diagnostics generated at compile time, seem like good goals.
The bootstrap with -fsanitize=undefined currently fails. One issue is http://gcc.gnu.org/ml/gcc-patches/2013-07/msg01480.html (-Wuninitialized needs fixing I'm afraid), and another is e.g.: switch (i) { case 0 * (1 / 0): ; } In the above, in C, we always fail (check_case_value issues "error: case label does not reduce to an integer constant"). But in C++, with -fsanitize=undefined, we get error: ‘__builtin___ubsan_handle_divrem_overflow((& *.Lubsan_data0), 1u, 0u)’ is not a constant expression and without sanitizing, there's no error (of course the behavior is undefined). I'm not sure how to deal with this, clang in both C/C++ says error: expression is not an integral constant expression It seems that this should be handled in semantics.c:verify_constant, but the function gets <integer_cst ... constant 0> as a tree parameter... Other than that, currently no other issues leap to mind; I ran gcc.dg/*const-expr* tests with -fsanitize=undefined and everything's fine, gcc.dg/overflow-warn* has some failures, all due to "case 0 * (1 / 0)" issue. Thanks, Marek
