Hi! On the following testcase, the C FE decides to shorten the division because it has a guarantee that INT_MIN / -1 division won't be encountered, the first operand is widened from narrower unsigned and/or the second operand is a constant other than all ones (in this case both are true). The problem is that the narrower type in this case is _Bool and ubsan_instrument_division only instruments it if op0's type is INTEGER_TYPE or REAL_TYPE. Strangely this doesn't happen in C++ FE. Anyway, we only shorten divisions if the INT_MIN / -1 case is impossible, so I think we should be fine even with -fstrict-enums in C++ in case it shortened to ENUMERAL_TYPEs.
The following patch just instruments those on the ubsan_instrument_division side. Perhaps only the first hunk and testcase might be needed because we shouldn't shorten if the other case could be triggered. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk, or shall I omit the second hunk? 2023-03-17 Jakub Jelinek <ja...@redhat.com> PR c/109151 * c-ubsan.cc (ubsan_instrument_division): Handle all scalar integral types rather than just INTEGER_TYPE. * c-c++-common/ubsan/div-by-zero-8.c: New test. --- gcc/c-family/c-ubsan.cc.jj 2023-02-28 11:38:28.965868044 +0100 +++ gcc/c-family/c-ubsan.cc 2023-03-16 09:49:51.651126302 +0100 @@ -53,7 +53,7 @@ ubsan_instrument_division (location_t lo op0 = unshare_expr (op0); op1 = unshare_expr (op1); - if (TREE_CODE (type) == INTEGER_TYPE + if (INTEGRAL_TYPE_P (type) && sanitize_flags_p (SANITIZE_DIVIDE)) t = fold_build2 (EQ_EXPR, boolean_type_node, op1, build_int_cst (type, 0)); @@ -68,7 +68,7 @@ ubsan_instrument_division (location_t lo t = NULL_TREE; /* We check INT_MIN / -1 only for signed types. */ - if (TREE_CODE (type) == INTEGER_TYPE + if (INTEGRAL_TYPE_P (type) && sanitize_flags_p (SANITIZE_SI_OVERFLOW) && !TYPE_UNSIGNED (type)) { --- gcc/testsuite/c-c++-common/ubsan/div-by-zero-8.c.jj 2023-03-16 10:01:31.626824994 +0100 +++ gcc/testsuite/c-c++-common/ubsan/div-by-zero-8.c 2023-03-16 10:03:05.510443440 +0100 @@ -0,0 +1,14 @@ +/* PR c/109151 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=integer-divide-by-zero -Wno-div-by-zero -fno-sanitize-recover=integer-divide-by-zero" } */ +/* { dg-shouldfail "ubsan" } */ + +int d; + +int +main () +{ + d = ((short) (d == 1 | d > 9)) / 0; +} + +/* { dg-output "division by zero" } */ Jakub