From: Michal Jires <mjires@suse.cz>
Date: Fri, 30 Jan 2026 15:42:48 +0000 (+0100)
Subject: c,c++: Fix incorrect warning with asm defined symbols
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa20d1d7095122c7fc0e701b08ec383a60404bb0;p=thirdparty%2Fgcc.git

c,c++: Fix incorrect warning with asm defined symbols

Static symbols defined in assembly cause wrong "used but never defined"
warning.

static void asm_fn();
asm("%cc0:" :: ":"(&asm_fn));

This happens in C,C++ frontends before cgraph is created where the
relevant flags are located.

We can suppress these warnings with OPT_Wunused.
C,C++ frontends and cgraphunit suppressed OPT_Wunused and
OPT_Wunused_function interchangeably, so we unify suppression to
only OPT_Wunused.

	PR testsuite/123559

gcc/c/ChangeLog:

	* c-decl.cc (c_write_global_declarations_1): Check and suppress
	OPT_Wunused.
	* c-typeck.cc (build_asm_expr): Suppress OPT_Wunused.

gcc/ChangeLog:

	* cgraphunit.cc (check_global_declaration): Suppress OPT_Wunused.

gcc/cp/ChangeLog:

	* decl.cc (wrapup_namespace_globals): Check and suppress OPT_Wunused.
	* semantics.cc (finish_asm_stmt): Suppress OPT_Wunused.

gcc/testsuite/ChangeLog:

	* c-c++-common/toplevel-extended-asm-1.c: New test.
---

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 7dddc23b5e1..ea0eaec0bb5 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -13679,25 +13679,22 @@ c_write_global_declarations_1 (tree globals)
       if (TREE_CODE (decl) == FUNCTION_DECL
 	  && DECL_INITIAL (decl) == NULL_TREE
 	  && DECL_EXTERNAL (decl)
-	  && !TREE_PUBLIC (decl))
+	  && !TREE_PUBLIC (decl)
+	  && !warning_suppressed_p (decl, OPT_Wunused))
 	{
 	  if (C_DECL_USED (decl))
 	    {
-	      /* TODO: Add OPT_Wundefined-inline.  */
 	      if (pedwarn (input_location, 0, "%q+F used but never defined",
 			   decl))
-		suppress_warning (decl /* OPT_Wundefined-inline.  */);
+		suppress_warning (decl, OPT_Wunused);
 	    }
 	  /* For -Wunused-function warn about unused static prototypes.  */
 	  else if (warn_unused_function
 		   && ! DECL_ARTIFICIAL (decl)
-		   && ! warning_suppressed_p (decl, OPT_Wunused_function))
-	    {
-	      if (warning (OPT_Wunused_function,
-			   "%q+F declared %<static%> but never defined",
-			   decl))
-		suppress_warning (decl, OPT_Wunused_function);
-	    }
+		   && warning (OPT_Wunused_function,
+			       "%q+F declared %<static%> but never defined",
+			       decl))
+	    suppress_warning (decl, OPT_Wunused);
 	}
 
       wrapup_global_declaration_1 (decl);
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 098a4b55339..dc803dc6388 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -13170,6 +13170,8 @@ build_asm_expr (location_t loc, tree string, tree outputs, tree inputs,
 				 "of a function or non-automatic variable");
 		  input = error_mark_node;
 		}
+	      else if (TREE_CODE (TREE_OPERAND (t, 0)) == FUNCTION_DECL)
+		suppress_warning (TREE_OPERAND (t, 0), OPT_Wunused);
 	    }
 	}
       else
diff --git a/gcc/cgraphunit.cc b/gcc/cgraphunit.cc
index 88c1071c8de..b0a0061abb5 100644
--- a/gcc/cgraphunit.cc
+++ b/gcc/cgraphunit.cc
@@ -1111,10 +1111,13 @@ check_global_declaration (symtab_node *snode)
       if (warning_suppressed_p (decl, OPT_Wunused))
 	;
       else if (snode->referred_to_p (/*include_self=*/false))
-	pedwarn (input_location, 0, "%q+F used but never defined", decl);
-      else
-	warning (OPT_Wunused_function, "%q+F declared %<static%> but never "
-				       "defined", decl);
+	{
+	  if (pedwarn (input_location, 0, "%q+F used but never defined", decl))
+	    suppress_warning (decl, OPT_Wunused);
+	}
+      else if (warning (OPT_Wunused_function,
+			"%q+F declared %<static%> but never defined", decl))
+	suppress_warning (decl, OPT_Wunused);
     }
 
   /* Warn about static fns or vars defined but not used.  */
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 6dabf349bef..c6aac6a8779 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -1015,10 +1015,11 @@ wrapup_namespace_globals ()
 	      && !TREE_PUBLIC (decl)
 	      && !DECL_ARTIFICIAL (decl)
 	      && !DECL_FRIEND_PSEUDO_TEMPLATE_INSTANTIATION (decl)
-	      && !warning_suppressed_p (decl, OPT_Wunused_function))
-	    warning_at (DECL_SOURCE_LOCATION (decl),
-			OPT_Wunused_function,
-			"%qF declared %<static%> but never defined", decl);
+	      && !warning_suppressed_p (decl, OPT_Wunused)
+	      && warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wunused_function,
+			     "%qF declared %<static%> but never defined",
+			     decl))
+		suppress_warning (decl, OPT_Wunused);
 
 	  if (VAR_P (decl)
 	      && DECL_EXTERNAL (decl)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index fb1be25edf5..236bc625c25 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2495,6 +2495,8 @@ finish_asm_stmt (location_t loc, int volatile_p, tree string,
 				"of a function or non-automatic variable");
 		      operand = error_mark_node;
 		    }
+		  else if (TREE_CODE (TREE_OPERAND (t, 0)) == FUNCTION_DECL)
+		    suppress_warning (TREE_OPERAND (t, 0), OPT_Wunused);
 		}
 	    }
 	  else
diff --git a/gcc/testsuite/c-c++-common/toplevel-extended-asm-1.c b/gcc/testsuite/c-c++-common/toplevel-extended-asm-1.c
new file mode 100644
index 00000000000..531c9423165
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/toplevel-extended-asm-1.c
@@ -0,0 +1,5 @@
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+static void asm_fn(); /* { dg-bogus "but never defined" } */
+asm("%cc0:" :: ":"(&asm_fn));