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c, c++, cgraphunit: Prevent duplicated -Wunused-value warnings [PR108079]

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On the following testcase, we warn with -Wunused-value twice, once
in the FEs and later on cgraphunit again with slightly different
wording.

The following patch fixes that by registering a warning suppression in the
FEs when we warn and not warning in cgraphunit anymore if that happened.

2023-03-10  Jakub Jelinek  <jakub@redhat.com>

	PR c/108079
gcc/
	* cgraphunit.cc (check_global_declaration): Don't warn for unused
	variables which have OPT_Wunused_variable warning suppressed.
gcc/c/
	* c-decl.cc (pop_scope): Suppress OPT_Wunused_variable warning
	after diagnosing it.
gcc/cp/
	* decl.cc (poplevel): Suppress OPT_Wunused_variable warning
	after diagnosing it.
gcc/testsuite/
	* c-c++-common/Wunused-var-18.c: New test.
This commit is contained in:
Jakub Jelinek 2023-03-10 10:10:24 +01:00
parent a1d5c729ce
commit 2c63cc7268
4 changed files with 16 additions and 1 deletions
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5
gcc/c/c-decl.cc
View file

@ -1310,7 +1310,10 @@ pop_scope (void)
&& scope != external_scope)
{
if (!TREE_USED (p))
warning (OPT_Wunused_variable, "unused variable %q+D", p);
{
warning (OPT_Wunused_variable, "unused variable %q+D", p);
suppress_warning (p, OPT_Wunused_variable);
}
else if (DECL_CONTEXT (p) == current_function_decl)
warning_at (DECL_SOURCE_LOCATION (p),
OPT_Wunused_but_set_variable,

1
gcc/cgraphunit.cc
View file

@ -1120,6 +1120,7 @@ check_global_declaration (symtab_node *snode)
&& (TREE_CODE (decl) != FUNCTION_DECL
|| (!DECL_STATIC_CONSTRUCTOR (decl)
&& !DECL_STATIC_DESTRUCTOR (decl)))
&& (! VAR_P (decl) || !warning_suppressed_p (decl, OPT_Wunused_variable))
/* Otherwise, ask the language. */
&& lang_hooks.decls.warn_unused_global (decl))
warning_at (DECL_SOURCE_LOCATION (decl),

1
gcc/cp/decl.cc
View file

@ -693,6 +693,7 @@ poplevel (int keep, int reverse, int functionbody)
else
warning_at (DECL_SOURCE_LOCATION (decl),
OPT_Wunused_variable, "unused variable %qD", decl);
suppress_warning (decl, OPT_Wunused_variable);
}
else if (DECL_CONTEXT (decl) == current_function_decl
// For -Wunused-but-set-variable leave references alone.

10
gcc/testsuite/c-c++-common/Wunused-var-18.c Normal file
View file

@ -0,0 +1,10 @@
/* PR c/108079 */
/* { dg-do compile } */
/* { dg-options "-Wunused-variable" } */
int
main ()
{
static int x; /* { dg-warning "unused variable 'x'" } */
/* { dg-bogus "'x' defined but not used" "" { target *-*-* } .-1 } */
}