Set and test no-warning bit to avoid -Wnonnull for synthesized expressions.

Resolves:
PR c++/96003 spurious -Wnonnull calling a member on the result of static_cast

gcc/c-family/ChangeLog:

	PR c++/96003
	* c-common.c (check_function_arguments_recurse): Return early when
	no-warning bit is set.

gcc/cp/ChangeLog:

	PR c++/96003
	* class.c (build_base_path): Set no-warning bit on the synthesized
	conditional expression in static_cast.

gcc/testsuite/ChangeLog:

	PR c++/96003
	* g++.dg/warn/Wnonnull7.C: New test.

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index b97539c0c2aa88c9743108b4b5e34cfab5cafaf3..96ed2334863cb21fcf02f02c7afcd68e3151ea6f 100644 (file)
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -5822,6 +5822,9 @@ check_function_arguments_recurse (void (*callback)
                                  void *ctx, tree param,
                                  unsigned HOST_WIDE_INT param_num)
 {
+  if (TREE_NO_WARNING (param))
+    return;
+
   if (CONVERT_EXPR_P (param)
       && (TYPE_PRECISION (TREE_TYPE (param))
          == TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (param, 0)))))

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 7a25d8fc76c381ddfd3ae0f6bd551c6b36f1faff..b39bdaaa3ab7b0379b891b79bd8383ad0871ecd0 100644 (file)
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -516,8 +516,14 @@ build_base_path (enum tree_code code,
 
  out:
   if (null_test)
-    expr = fold_build3_loc (input_location, COND_EXPR, target_type, null_test, expr,
-                           build_zero_cst (target_type));
+    {
+      expr = fold_build3_loc (input_location, COND_EXPR, target_type, null_test,
+                             expr, build_zero_cst (target_type));
+      /* Avoid warning for the whole conditional expression (in addition
+        to NULL_TEST itself -- see above) in case the result is used in
+        a nonnull context that the front end -Wnonnull checks.  */
+      TREE_NO_WARNING (expr) = 1;
+    }
 
   return expr;
 }

diff --git a/gcc/testsuite/g++.dg/warn/Wnonnull7.C b/gcc/testsuite/g++.dg/warn/Wnonnull7.C
new file mode 100644 (file)
index 0000000..7611c18
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wnonnull7.C
@@ -0,0 +1,36 @@
+/* PR c++/96003 - spurious -Wnonnull calling a member on the result
+   of static_cast
+   { dg-do compile }
+   { dg-options "-Wall" } */
+
+struct D;
+struct B
+{
+  B* next;
+  D* Next ();
+};
+
+struct D: B
+{
+  virtual ~D ();
+};
+
+struct Iterator
+{
+  D* p;
+  void advance ()
+  {
+    p = static_cast<B*>(p)->Next ();    // { dg-bogus "\\\[-Wnonnull" }
+  }
+};
+
+// Test case from comment #11.
+
+struct S1 { virtual ~S1 (); };
+struct S2 { virtual ~S2 (); };
+struct S3: S1, S2 { void f (); };
+
+void f (S2 *p)
+{
+  static_cast<S3 *>(p)->f ();           // { dg-bogus "\\\[-Wnonnull" }
+}