[Bug c/99588] variable set but not used warning on static _Atomic assignment
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Fri Mar 19 21:55:35 GMT 2021
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99588
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:3279a9a5a9a2e4e17175678cb7b15613495e306e
commit r11-7746-g3279a9a5a9a2e4e17175678cb7b15613495e306e
Author: Jakub Jelinek <jakub@redhat.com>
Date: Fri Mar 19 22:54:31 2021 +0100
c: Fix up -Wunused-but-set-* warnings for _Atomics [PR99588]
As the following testcases show, compared to -D_Atomic= case we have many
-Wunused-but-set-* warning false positives.
When an _Atomic variable/parameter is read, we call mark_exp_read on it in
convert_lvalue_to_rvalue, but build_atomic_assign does not.
For consistency with the non-_Atomic case where we mark_exp_read the lhs
for lhs op= ... but not for lhs = ..., this patch does that too.
But furthermore we need to pattern match the trees emitted by _Atomic
store,
so that _Atomic store itself is not marked as being a variable read, but
when the result of the store is used, we mark it.
2021-03-19 Jakub Jelinek <jakub@redhat.com>
PR c/99588
* c-typeck.c (mark_exp_read): Recognize what build_atomic_assign
with modifycode NOP_EXPR produces and mark the _Atomic var as read
if found.
(build_atomic_assign): For modifycode of NOP_EXPR, use
COMPOUND_EXPRs
rather than STATEMENT_LIST. Otherwise call mark_exp_read on lhs.
Set TREE_SIDE_EFFECTS on the TARGET_EXPR.
* gcc.dg/Wunused-var-5.c: New test.
* gcc.dg/Wunused-var-6.c: New test.
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