From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2140) id 987563876053; Sun, 19 Nov 2023 07:02:17 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 987563876053 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1700377337; bh=t17FCZQnbUlC4fnC+BYzdmgruTwrhdEfWLpyx6Fjfrs=; h=From:To:Subject:Date:From; b=tbztZgy8OQsXORox8++ES1Fx69k1awKg8PTGUEo22lopyZsKutHt5Rwyp3yBQvbjP rvcwyEqyYPioR9KO37HsjxxG3i8RAVUuyRbLKAwrgT5SmXRjb23W2MrG2QIfbTTlYv U2uZTou2HKAdJA0mQbk1fdfONOjmxkHnq+VcesDo= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Alexandre Oliva To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/users/aoliva/heads/testme)] warn on cast of pointer to packed plus constant X-Act-Checkin: gcc X-Git-Author: Alexandre Oliva X-Git-Refname: refs/users/aoliva/heads/testme X-Git-Oldrev: 48dece46f1b5ea2fa7b3bf8c8165047484073a7c X-Git-Newrev: 9d7a231e7496533834e194131a0971a533534d3b Message-Id: <20231119070217.987563876053@sourceware.org> Date: Sun, 19 Nov 2023 07:02:17 +0000 (GMT) List-Id: https://gcc.gnu.org/g:9d7a231e7496533834e194131a0971a533534d3b commit 9d7a231e7496533834e194131a0971a533534d3b Author: Alexandre Oliva Date: Sun Nov 19 01:25:01 2023 -0300 warn on cast of pointer to packed plus constant 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. 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. Diff: --- gcc/c-family/c-warn.cc | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc index d2938b91043..39f5ddc577c 100644 --- a/gcc/c-family/c-warn.cc +++ b/gcc/c-family/c-warn.cc @@ -3108,9 +3108,17 @@ 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); nop_p |= orig_rhs != rhs; }