public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/108395] New: [C2x] Bogus -Wunused-but-set-variable when returning constexpr variable
@ 2023-01-13 14:58 pexu@gcc-bugzilla.mail.kapsi.fi
2023-01-13 20:31 ` [Bug c/108395] " pinskia at gcc dot gnu.org
2023-01-13 22:26 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: pexu@gcc-bugzilla.mail.kapsi.fi @ 2023-01-13 14:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108395
Bug ID: 108395
Summary: [C2x] Bogus -Wunused-but-set-variable when returning
constexpr variable
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: pexu@gcc-bugzilla.mail.kapsi.fi
Target Milestone: ---
Hi.
It appears if constexpr variable, declared at block scope, is used verbatim as
a return value GCC emits a bogus -Wunused-but-set-variable.
Using version `13.0.0 20230113 (experimental)'.
# echo 'int f() { constexpr int v = 0; return v; }' | gcc -c -xc -std=c2x -Wall
-Wextra -
<stdin>: In function 'f':
<stdin>:1:25: warning: variable 'v' set but not used
[-Wunused-but-set-variable]
As a workaround any operation on v (cast, effectively-no-op arithmetics etc.)
or maybe_unused attribute (or file scope) can be used.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/108395] [C2x] Bogus -Wunused-but-set-variable when returning constexpr variable
2023-01-13 14:58 [Bug c/108395] New: [C2x] Bogus -Wunused-but-set-variable when returning constexpr variable pexu@gcc-bugzilla.mail.kapsi.fi
@ 2023-01-13 20:31 ` pinskia at gcc dot gnu.org
2023-01-13 22:26 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-13 20:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108395
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |89180
Ever confirmed|0 |1
Last reconfirmed| |2023-01-13
Status|UNCONFIRMED |NEW
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89180
[Bug 89180] [meta-bug] bogus/missing -Wunused warnings
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/108395] [C2x] Bogus -Wunused-but-set-variable when returning constexpr variable
2023-01-13 14:58 [Bug c/108395] New: [C2x] Bogus -Wunused-but-set-variable when returning constexpr variable pexu@gcc-bugzilla.mail.kapsi.fi
2023-01-13 20:31 ` [Bug c/108395] " pinskia at gcc dot gnu.org
@ 2023-01-13 22:26 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-13 22:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108395
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is will most likely fix it, but I am not 100% sure it fixes all of the
constexpr cases though:
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index e06f052eb46..3a169eceece 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -2154,7 +2154,10 @@ maybe_get_constexpr_init (tree expr)
&& C_DECL_DECLARED_CONSTEXPR (decl)
&& DECL_INITIAL (decl) != NULL_TREE
&& !error_operand_p (DECL_INITIAL (decl)))
- return DECL_INITIAL (decl);
+ {
+ mark_exp_read (decl);
+ return DECL_INITIAL (decl);
+ }
if (TREE_CODE (expr) != COMPONENT_REF)
return NULL_TREE;
tree inner = maybe_get_constexpr_init (TREE_OPERAND (expr, 0));
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-01-13 22:26 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-01-13 14:58 [Bug c/108395] New: [C2x] Bogus -Wunused-but-set-variable when returning constexpr variable pexu@gcc-bugzilla.mail.kapsi.fi
2023-01-13 20:31 ` [Bug c/108395] " pinskia at gcc dot gnu.org
2023-01-13 22:26 ` pinskia at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).