https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103881
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:4e8c32ecfb87e723229dc6c08df8ea602e947f1e commit r10-10666-g4e8c32ecfb87e723229dc6c08df8ea602e947f1e Author: Jakub Jelinek <ja...@redhat.com> Date: Tue Jan 11 19:11:51 2022 +0100 c-family: Fix up -W*conversion on bitwise &/|/^ [PR101537] The following testcases emit a bogus -Wconversion warning. This is because conversion_warning function doesn't handle BIT_*_EXPR (only unsafe_conversion_p that is called during the default: case, and that one doesn't handle SAVE_EXPRs added because the unsigned char & or | operands promoted to int have side-effects and =| or =& is used. The patch handles BIT_IOR_EXPR/BIT_XOR_EXPR like the last 2 operands of COND_EXPR by recursing on the two operands, if either of them doesn't fit into the narrower type, complain. BIT_AND_EXPR too, but first it needs to handle some special cases that unsafe_conversion_p does, namely when one of the two operands is a constant. This fixes completely the pr101537.c test and for C also pr103881.c and doesn't regress anything in the testsuite, for C++ pr103881.c still emits the bogus warnings. This is because while the C FE emits in that case a SAVE_EXPR that conversion_warning can handle already, C++ FE emits TARGET_EXPR <D.whatever, ...>, something | D.whatever etc. and conversion_warning handles COMPOUND_EXPR by "recursing" on the rhs. To handle that case, we'd need for TARGET_EXPR on the lhs remember in some hash map the mapping from D.whatever to the TARGET_EXPR and when we see D.whatever, use corresponding TARGET_EXPR initializer instead. 2022-01-11 Jakub Jelinek <ja...@redhat.com> PR c/101537 PR c/103881 gcc/c-family/ * c-warn.c (conversion_warning): Handle BIT_AND_EXPR, BIT_IOR_EXPR and BIT_XOR_EXPR. gcc/testsuite/ * c-c++-common/pr101537.c: New test. * c-c++-common/pr103881.c: New test. (cherry picked from commit 20e4a5e573e76f4379b353cc736215a5f10cdb84)
