typeck.c (build_binary_op): Issue warning if either operand of a comparison operator is a string literal...

	* typeck.c (build_binary_op): Issue warning if either operand of a
	comparison operator is a string literal, except for testing equality
	or inequality against NULL.

	* g++.dg/warn/Wstring-literal-comparison-1.C: New test case.
	* g++.dg/warn/Wstring-literal-comparison-2.C: Likewise.
	* g++.dg/warn/Wstring-literal-comparison-3.C: Likewise.
	* g++.dg/warn/Wstring-literal-comparison-4.C: Likewise.

From-SVN: r108120

7 files changed, 138 insertions, 0 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 82b99cb..d133d8b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,11 @@
 2005-12-06  Roger Sayle  <roger@eyesopen.com>
 
+	* typeck.c (build_binary_op): Issue warning if either operand of a
+	comparison operator is a string literal, except for testing equality
+	or inequality against NULL.
+
+2005-12-06  Roger Sayle  <roger@eyesopen.com>
+
 	PR c++/25263
 	* decl.c (compute_array_index_type): Check that itype is an
 	INTEGER_CST node before testing/clearing TREE_OVERFLOW.
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 0ee630a..0cae938 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -3089,6 +3089,10 @@ build_binary_op (enum tree_code code, tree orig_op0, tree orig_op1,
     case NE_EXPR:
       if (warn_float_equal && (code0 == REAL_TYPE || code1 == REAL_TYPE))
 	warning (0, "comparing floating point with == or != is unsafe");
+      if ((TREE_CODE (orig_op0) == STRING_CST && !integer_zerop (op1))
+	  || (TREE_CODE (orig_op1) == STRING_CST && !integer_zerop (op0)))
+	warning (OPT_Wstring_literal_comparison,
+		 "comparison with string literal");
 
       build_type = boolean_type_node;
       if ((code0 == INTEGER_TYPE || code0 == REAL_TYPE
@@ -3194,6 +3198,11 @@ build_binary_op (enum tree_code code, tree orig_op0, tree orig_op1,
     case GE_EXPR:
     case LT_EXPR:
     case GT_EXPR:
+      if (TREE_CODE (orig_op0) == STRING_CST
+	  || TREE_CODE (orig_op1) == STRING_CST)
+	warning (OPT_Wstring_literal_comparison,
+		 "comparison with string literal");
+
       build_type = boolean_type_node;
       if ((code0 == INTEGER_TYPE || code0 == REAL_TYPE)
 	   && (code1 == INTEGER_TYPE || code1 == REAL_TYPE))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 6c16c7d..35f45ea 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,12 @@
 2005-12-06  Roger Sayle  <roger@eyesopen.com>
 
+	* g++.dg/warn/Wstring-literal-comparison-1.C: New test case.
+	* g++.dg/warn/Wstring-literal-comparison-2.C: Likewise.
+	* g++.dg/warn/Wstring-literal-comparison-3.C: Likewise.
+	* g++.dg/warn/Wstring-literal-comparison-4.C: Likewise.
+
+2005-12-06  Roger Sayle  <roger@eyesopen.com>
+
 	PR c++/25263
 	* g++.dg/other/array2.C: New test case.
 
diff --git a/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-1.C b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-1.C
new file mode 100644
index 0000000..c5dea46
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-1.C
@@ -0,0 +1,29 @@
+/* PR c/7776 */
+/* { dg-do compile } */
+/* { dg-options "-Wstring-literal-comparison" } */
+
+int test1(char *ptr)
+{
+  return ptr == "foo";  /* { dg-warning "comparison with string" } */
+}
+
+int test2()
+{
+  return "foo" != (const char*)0;
+}
+
+int test3()
+{
+  return "foo" == (const char*)0;
+}
+
+int test4()
+{
+  return (const char*)0 != "foo";
+}
+
+int test5()
+{
+  return (const char*)0 == "foo";
+}
+
diff --git a/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-2.C b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-2.C
new file mode 100644
index 0000000..3eb91ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-2.C
@@ -0,0 +1,29 @@
+/* PR c/7776 */
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+int test1(char *ptr)
+{
+  return ptr == "foo";  /* { dg-warning "comparison with string" } */
+}
+
+int test2()
+{
+  return "foo" != (const char*)0;
+}
+
+int test3()
+{
+  return "foo" == (const char*)0;
+}
+
+int test4()
+{
+  return (const char*)0 != "foo";
+}
+
+int test5()
+{
+  return (const char*)0 == "foo";
+}
+
diff --git a/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-3.C b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-3.C
new file mode 100644
index 0000000..f700a51
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-3.C
@@ -0,0 +1,29 @@
+/* PR c/7776 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+int test1(char *ptr)
+{
+  return ptr == "foo";
+}
+
+int test2()
+{
+  return "foo" != (const char*)0;
+}
+
+int test3()
+{
+  return "foo" == (const char*)0;
+}
+
+int test4()
+{
+  return (const char*)0 != "foo";
+}
+
+int test5()
+{
+  return (const char*)0 == "foo";
+}
+
diff --git a/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-4.C b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-4.C
new file mode 100644
index 0000000..27f25f3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wstring-literal-comparison-4.C
@@ -0,0 +1,29 @@
+/* PR c/7776 */
+/* { dg-do compile } */
+/* { dg-options "-Wall -Wno-string-literal-comparison" } */
+
+int test1(char *ptr)
+{
+  return ptr == "foo";
+}
+
+int test2()
+{
+  return "foo" != (const char*)0;
+}
+
+int test3()
+{
+  return "foo" == (const char*)0;
+}
+
+int test4()
+{
+  return (const char*)0 != "foo";
+}
+
+int test5()
+{
+  return (const char*)0 == "foo";
+}
+