[PATCH] handle member references in -Waddress [PR96507]

[Martin Sebor via Gcc-patches]

While going through old -Waddress bug reports to close after
the recent improvements to the warning I came across PR 96507
that points out that member references aren't handled.  Since
testing the address of a reference for equality to null is
in general diagnosed, this seems like an oversight worth fixing.
 Attached is a change to the C++ front end to diagnose member
references as well.

Tested on x86_64-linux.

Martin

Issue -Waddress also for reference members [PR96507].

Resolves:
PR c++/96507 - missing -Waddress for member references

gcc/cp/ChangeLog:

	PR c++/96507
	* typeck.c (warn_for_null_address): Handle reference members.

gcc/testsuite/ChangeLog:

	PR c++/96507
	* g++.dg/warn/Waddress-8.C: New test.

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 58919aaf13e..694c53eef8a 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -4676,15 +4676,21 @@ warn_for_null_address (location_t location, tree op, tsubst_flags_t complain)
 		    "addition %qE and NULL", cop);
       return;
     }
-  else if (CONVERT_EXPR_P (op)
-      && TYPE_REF_P (TREE_TYPE (TREE_OPERAND (op, 0))))
+  else if (CONVERT_EXPR_P (op))
     {
-      STRIP_NOPS (op);
+      tree op0 = TREE_OPERAND (op, 0);
+      if (TYPE_REF_P (TREE_TYPE (op0)))
+	{
+	  STRIP_NOPS (op);
+
+	  if (TREE_CODE (op) == COMPONENT_REF)
+	    op = TREE_OPERAND (op, 1);
 
-      if (DECL_P (op))
-	warned = warning_at (location, OPT_Waddress,
-			     "the compiler can assume that the address of "
-			     "%qD will never be NULL", op);
+	  if (DECL_P (op))
+	    warned = warning_at (location, OPT_Waddress,
+				 "the compiler can assume that the address of "
+				 "%qD will never be NULL", op);
+	}
     }
 
   if (warned && DECL_P (op))
diff --git a/gcc/testsuite/g++.dg/warn/Waddress-8.C b/gcc/testsuite/g++.dg/warn/Waddress-8.C
new file mode 100644
index 00000000000..797102d6be4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Waddress-8.C
@@ -0,0 +1,85 @@
+/* PR c++/96507 - missing -Waddress for member references
+   { dg-do compile }
+   { dg-options "-Wall" } */
+
+typedef void F ();
+
+extern F 𝔢
+extern int &eir;
+
+bool warn_ext_rfun ()
+{
+  return &efr != 0;           // { dg-warning "-Waddress" }
+}
+
+bool warn_ext_rvar ()
+{
+  return &eir != 0;           // { dg-warning "-Waddress" }
+}
+
+
+bool warn_parm_rfun (F &rf)
+{
+  return &rf != 0;            // { dg-warning "-Waddress" }
+}
+
+bool warn_parm_rvar (int &ir)
+{
+  return &ir != 0;            // { dg-warning "-Waddress" }
+}
+
+// Comparing the address of a reference argument to null also triggers
+// a -Wnonnull-compare (that seems like a bug, hence PR 103363).
+// { dg-prune-output "-Wnonnull-compare" }
+
+
+struct S
+{
+  F &fr;
+  int &ir;
+};
+
+extern S es, esa[];
+
+bool warn_ext_mem_rfun ()
+{
+  return &es.fr != 0;         // { dg-warning "-Waddress" }
+}
+
+bool warn_ext_mem_rvar ()
+{
+  return &es.ir != 0;         // { dg-warning "-Waddress" }
+}
+
+
+bool warn_ext_arr_mem_rfun (int i)
+{
+  return &esa[i].fr != 0;     // { dg-warning "-Waddress" }
+}
+
+bool warn_ext_arr_mem_rvar (int i)
+{
+  return &esa[i].ir != 0;     // { dg-warning "-Waddress" }
+}
+
+
+bool warn_parm_mem_rfun (S &s)
+{
+  return &s.fr != 0;          // { dg-warning "-Waddress" }
+}
+
+bool warn_parm_mem_rvar (S &s)
+{
+  return &s.ir != 0;          // { dg-warning "-Waddress" }
+}
+
+
+bool warn_parm_arr_mem_rfun (S sa[], int i)
+{
+  return &sa[i].fr != 0;      // { dg-warning "-Waddress" }
+}
+
+bool warn_parm_arr_mem_rvar (S sa[], int i)
+{
+  return &sa[i].ir != 0;      // { dg-warning "-Waddress" }
+}