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

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.

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 91599658be9650a887e88774a5dc0c5502bb2301..e537d33f3986083c039f671bcf5eb4c6f0408300 100644 (file)
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -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,

diff --git a/gcc/cgraphunit.cc b/gcc/cgraphunit.cc
index a972900900b71bfe48db39783f0b17a3fb2d6ec7..e12764f2f906ec3f605ca43d9d1870d68179def9 100644 (file)
--- a/gcc/cgraphunit.cc
+++ b/gcc/cgraphunit.cc
@@ -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),

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index b1603859644fe40a989bbfebacb9aa29584847ff..51199bb311a89d2ab1805faf168499f61a49dbc3 100644 (file)
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -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.

diff --git a/gcc/testsuite/c-c++-common/Wunused-var-18.c b/gcc/testsuite/c-c++-common/Wunused-var-18.c
new file mode 100644 (file)
index 0000000..5ff772b
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wunused-var-18.c
@@ -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 } */
+}