c-c++-common/analyzer/null-deref-pr108251-smp-fetch_ssl_fc_has_early.c gets an unaligned pointer value warning on -fshort-enums targets in C, but not in C++. The former simplifies the offset-and-cast expression enough that check_and_warn_address_or_pointer_of_packed_member finds no more than a type cast of the base pointer, but in C++, the entire expression, with cast, constant offsetting, and cast again, is retained, and that's too much for the warning code.
Or rather it was. It's easy enough to take the base pointer from PLUS_POINTER_EXPR, and a constant offset can't possibly increase alignment for just any pointer of laxer alignment, so we can safely disregard the offset. This should improve the warning even in C, if the packed enum is at a nonzero offset into the containing struct. Regstrapped on x86_64-linux-gnu, also tested on arm-eabi with default cpu on trunk, and with tms570 on gcc-13. Ok to install? for gcc/c-family/ChangeLog * c-warn.cc (check_and_warn_address_or_pointer_of_packed_member): Take the base pointer from PLUS_POINTER_EXPR when the addend is constant. --- gcc/c-family/c-warn.cc | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc index d2938b91043d3..2ef73d7088f22 100644 --- a/gcc/c-family/c-warn.cc +++ b/gcc/c-family/c-warn.cc @@ -3108,10 +3108,20 @@ check_and_warn_address_or_pointer_of_packed_member (tree type, tree rhs) do { - while (TREE_CODE (rhs) == COMPOUND_EXPR) - rhs = TREE_OPERAND (rhs, 1); - orig_rhs = rhs; + do + { + orig_rhs = rhs; + while (TREE_CODE (rhs) == COMPOUND_EXPR) + rhs = TREE_OPERAND (rhs, 1); + /* Constants can't increase the alignment. */ + while (TREE_CODE (rhs) == POINTER_PLUS_EXPR + && TREE_CONSTANT (TREE_OPERAND (rhs, 1))) + rhs = TREE_OPERAND (rhs, 0); + } + while (orig_rhs != rhs); STRIP_NOPS (rhs); + while (TREE_CODE (rhs) == VIEW_CONVERT_EXPR) + rhs = TREE_OPERAND (rhs, 0); nop_p |= orig_rhs != rhs; } while (orig_rhs != rhs); -- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer More tolerance and less prejudice are key for inclusion and diversity Excluding neuro-others for not behaving ""normal"" is *not* inclusive