re PR c/64610 (No -Wbool-compare warning on "(0 != a) >= 0")

	PR c/64610
	* c-common.c (maybe_warn_bool_compare): Warn when comparing a boolean
	with 0/1.

	* c-c++-common/Wbool-compare-1.c (fn1): Remove a few lines.
	* c-c++-common/Wbool-compare-2.c: New test.

From-SVN: r222587

gcc/c-family/ChangeLog

+2015-04-29  Marek Polacek  <polacek@redhat.com>
+
+	PR c/64610
+	* c-common.c (maybe_warn_bool_compare): Warn when comparing a boolean
+	with 0/1.
+
 2015-04-29  Jakub Jelinek  <jakub@redhat.com>
 
 	* c-common.h (omp_clause_mask): Unconditionally define as a class.

gcc/c-family/c-common.c

@@ -11910,8 +11910,8 @@ maybe_warn_bool_compare (location_t loc, enum tree_code code, tree op0,
 
   if (!integer_zerop (cst) && !integer_onep (cst))
     {
-      int sign = (TREE_CODE (op0) == INTEGER_CST)
-		 ? tree_int_cst_sgn (cst) : -tree_int_cst_sgn (cst);
+      int sign = (TREE_CODE (op0) == INTEGER_CST
+		 ? tree_int_cst_sgn (cst) : -tree_int_cst_sgn (cst));
       if (code == EQ_EXPR
 	  || ((code == GT_EXPR || code == GE_EXPR) && sign < 0)
 	  || ((code == LT_EXPR || code == LE_EXPR) && sign > 0))
@@ -11921,6 +11921,18 @@ maybe_warn_bool_compare (location_t loc, enum tree_code code, tree op0,
 	warning_at (loc, OPT_Wbool_compare, "comparison of constant %qE "
 		    "with boolean expression is always true", cst);
     }
+  else if (integer_zerop (cst) || integer_onep (cst))
+    {
+      /* Do some magic to get the right diagnostics.  */
+      bool flag = TREE_CODE (op0) == INTEGER_CST;
+      flag = integer_zerop (cst) ? flag : !flag;
+      if ((code == GE_EXPR && !flag) || (code == LE_EXPR && flag))
+	warning_at (loc, OPT_Wbool_compare, "comparison of constant %qE "
+		    "with boolean expression is always true", cst);
+      else if ((code == LT_EXPR && !flag) || (code == GT_EXPR && flag))
+	warning_at (loc, OPT_Wbool_compare, "comparison of constant %qE "
+		    "with boolean expression is always false", cst);
+    }
 }
 
 /* The C and C++ parsers both use vectors to hold function arguments.

gcc/testsuite/ChangeLog

+2015-04-29  Marek Polacek  <polacek@redhat.com>
+
+	PR c/64610
+	* c-c++-common/Wbool-compare-1.c (fn1): Remove a few lines.
+	* c-c++-common/Wbool-compare-2.c: New test.
+
 2015-04-29  Alan Lawrence  <alan.lawrence@arm.com>
 
 	PR target/65770

gcc/testsuite/c-c++-common/Wbool-compare-1.c

@@ -72,15 +72,10 @@ fn1 (bool b)
   r = b == true;
   r = b != true;
 
-  /* Some of these don't make much sense, but we don't warn.  */
-  r = b < false;
-  r = b >= false;
   r = b <= false;
   r = b > false;
   r = b < true;
   r = b >= true;
-  r = b <= true;
-  r = b > true;
 }
 
 void

gcc/testsuite/c-c++-common/Wbool-compare-2.c

+/* PR c/64610 */
+/* { dg-do compile } */
+/* { dg-options "-Wbool-compare" } */
+
+#ifndef __cplusplus
+# define bool _Bool
+# define true 1
+# define false 0
+#endif
+
+extern bool foo (void);
+
+enum { A, B };
+
+int
+fn1 (bool b)
+{
+  int r = 0;
+
+  r += b >= 0; /* { dg-warning "with boolean expression is always true" } */
+  r += b > 0;
+  r += b < 0; /* { dg-warning "with boolean expression is always false" } */
+  r += b <= 0;
+
+  r += b >= 1;
+  r += b > 1; /* { dg-warning "with boolean expression is always false" } */
+  r += b < 1;
+  r += b <= 1; /* { dg-warning "with boolean expression is always true" } */
+
+  r += foo () >= 0; /* { dg-warning "with boolean expression is always true" } */
+  r += foo () > 0;
+  r += foo () < 0; /* { dg-warning "with boolean expression is always false" } */
+  r += foo () <= 0;
+
+  r += foo () >= 1;
+  r += foo () > 1; /* { dg-warning "with boolean expression is always false" } */
+  r += foo () < 1;
+  r += foo () <= 1; /* { dg-warning "with boolean expression is always true" } */
+
+  r += b >= A; /* { dg-warning "with boolean expression is always true" } */
+  r += b > A;
+  r += b < A; /* { dg-warning "with boolean expression is always false" } */
+  r += b <= A;
+
+  r += b >= B;
+  r += b > B; /* { dg-warning "with boolean expression is always false" } */
+  r += b < B;
+  r += b <= B; /* { dg-warning "with boolean expression is always true" } */
+
+  /* Swap LHS and RHS.  */
+  r += 0 >= b;
+  r += 0 > b; /* { dg-warning "with boolean expression is always false" } */
+  r += 0 < b;
+  r += 0 <= b; /* { dg-warning "with boolean expression is always true" } */
+
+  r += 1 >= b; /* { dg-warning "with boolean expression is always true" } */
+  r += 1 > b;
+  r += 1 < b; /* { dg-warning "with boolean expression is always false" } */
+  r += 1 <= b;
+
+  r += 0 >= foo ();
+  r += 0 > foo (); /* { dg-warning "with boolean expression is always false" } */
+  r += 0 < foo ();
+  r += 0 <= foo (); /* { dg-warning "with boolean expression is always true" } */
+
+  r += 1 >= foo (); /* { dg-warning "with boolean expression is always true" } */
+  r += 1 > foo ();
+  r += 1 < foo (); /* { dg-warning "with boolean expression is always false" } */
+  r += 1 <= foo ();
+
+  r += A >= b;
+  r += A > b; /* { dg-warning "with boolean expression is always false" } */
+  r += A < b;
+  r += A <= b; /* { dg-warning "with boolean expression is always true" } */
+
+  r += B >= b; /* { dg-warning "with boolean expression is always true" } */
+  r += B > b;
+  r += B < b; /* { dg-warning "with boolean expression is always false" } */
+  r += B <= b;
+
+  return r;
+}
+
+int
+fn2 (int i, int j)
+{
+  int r = 0;
+
+  r += (i == j) >= 0; /* { dg-warning "with boolean expression is always true" } */
+  r += (i == j) > 0;
+  r += (i == j) < 0; /* { dg-warning "with boolean expression is always false" } */
+  r += (i == j) <= 0;
+
+  r += (i == j) >= 1;
+  r += (i == j) > 1; /* { dg-warning "with boolean expression is always false" } */
+  r += (i == j) < 1;
+  r += (i == j) <= 1; /* { dg-warning "with boolean expression is always true" } */
+
+  return r;
+}