From 4dc7ce6fb3917958d1a6036d8acf2953b9c1b868 Mon Sep 17 00:00:00 2001
From: Martin Sebor <msebor@redhat.com>
Date: Fri, 1 Oct 2021 11:50:25 -0600
Subject: Enhance -Waddress to detect more suspicious expressions [PR102103].

Resolves:
PR c/102103 - missing warning comparing array address to null

gcc/ChangeLog:

	PR c/102103
	* doc/invoke.texi (-Waddress): Update.
	* gengtype.c (write_types): Avoid -Waddress.
	* poly-int.h (POLY_SET_COEFF): Avoid using null.

gcc/c-family/ChangeLog:

	PR c/102103
	* c-common.c (decl_with_nonnull_addr_p): Handle members.
	Check and perform warning suppression.
	(c_common_truthvalue_conversion): Enhance warning suppression.

gcc/c/ChangeLog:

	PR c/102103
	* c-typeck.c (maybe_warn_for_null_address): New function.
	(build_binary_op): Call it.

gcc/cp/ChangeLog:

	PR c/102103
	* typeck.c (warn_for_null_address): Enhance.
	(cp_build_binary_op): Call it also for member pointers.

gcc/fortran/ChangeLog:

	PR c/102103
	* array.c: Remove an unnecessary test.
	* trans-array.c: Same.

gcc/testsuite/ChangeLog:

	PR c/102103
	* g++.dg/cpp0x/constexpr-array-ptr10.C: Suppress a valid warning.
	* g++.dg/warn/Wreturn-local-addr-6.C: Correct a cast.
	* gcc.dg/Waddress.c: Expect a warning.
	* c-c++-common/Waddress-3.c: New test.
	* c-c++-common/Waddress-4.c: New test.
	* g++.dg/warn/Waddress-5.C: New test.
	* g++.dg/warn/Waddress-6.C: New test.
	* g++.dg/warn/pr101219.C: Expect a warning.
	* gcc.dg/Waddress-3.c: New test.
---
 gcc/c-family/c-common.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

(limited to 'gcc/c-family/c-common.c')

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 5845c67..9d19e35 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -3393,14 +3393,16 @@ c_wrap_maybe_const (tree expr, bool non_const)
   return expr;
 }
 
-/* Return whether EXPR is a declaration whose address can never be
-   NULL.  */
+/* Return whether EXPR is a declaration whose address can never be NULL.
+   The address of the first struct member could be NULL only if it were
+   accessed through a NULL pointer, and such an access would be invalid.  */
 
 bool
 decl_with_nonnull_addr_p (const_tree expr)
 {
   return (DECL_P (expr)
-	  && (TREE_CODE (expr) == PARM_DECL
+	  && (TREE_CODE (expr) == FIELD_DECL
+	      || TREE_CODE (expr) == PARM_DECL
 	      || TREE_CODE (expr) == LABEL_DECL
 	      || !DECL_WEAK (expr)));
 }
@@ -3488,13 +3490,17 @@ c_common_truthvalue_conversion (location_t location, tree expr)
     case ADDR_EXPR:
       {
  	tree inner = TREE_OPERAND (expr, 0);
-	if (decl_with_nonnull_addr_p (inner))
+	if (decl_with_nonnull_addr_p (inner)
+	    /* Check both EXPR and INNER for suppression.  */
+	    && !warning_suppressed_p (expr, OPT_Waddress)
+	    && !warning_suppressed_p (inner, OPT_Waddress))
 	  {
-	    /* Common Ada programmer's mistake.  */
+	    /* Common Ada programmer's mistake.	 */
 	    warning_at (location,
 			OPT_Waddress,
 			"the address of %qD will always evaluate as %<true%>",
 			inner);
+	    suppress_warning (inner, OPT_Waddress);
 	    return truthvalue_true_node;
 	  }
 	break;
@@ -3627,8 +3633,17 @@ c_common_truthvalue_conversion (location_t location, tree expr)
 	  break;
 	/* If this isn't narrowing the argument, we can ignore it.  */
 	if (TYPE_PRECISION (totype) >= TYPE_PRECISION (fromtype))
-	  return c_common_truthvalue_conversion (location,
-						 TREE_OPERAND (expr, 0));
+	  {
+	    tree op0 = TREE_OPERAND (expr, 0);
+	    if ((TREE_CODE (fromtype) == POINTER_TYPE
+		 && TREE_CODE (totype) == INTEGER_TYPE)
+		|| warning_suppressed_p (expr, OPT_Waddress))
+	      /* Suppress -Waddress for casts to intptr_t, propagating
+		 any suppression from the enclosing expression to its
+		 operand.  */
+	      suppress_warning (op0, OPT_Waddress);
+	    return c_common_truthvalue_conversion (location, op0);
+	  }
       }
       break;
 
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