C++ PATCH to abate shift warnings (PR c++/68979)

[Marek Polacek]

On Tue, Jan 12, 2016 at 09:09:38AM -0500, Jason Merrill wrote:
> In that case, we need to return (!flag_permissive || ctx->quiet).

Thanks.  So is this one ok once it passes testing?

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2016-01-12  Marek Polacek  <polacek@redhat.com>

	PR c++/68979
	* constexpr.c (cxx_eval_check_shift_p): Use permerror rather than
	error_at and adjust the return value.

	* g++.dg/warn/permissive-1.C: New test.

diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index e60180e..36a1e42 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -1512,17 +1512,17 @@ cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx,
   if (tree_int_cst_sgn (rhs) == -1)
     {
       if (!ctx->quiet)
-	error_at (loc, "right operand of shift expression %q+E is negative",
-		  build2_loc (loc, code, type, lhs, rhs));
-      return true;
+	permerror (loc, "right operand of shift expression %q+E is negative",
+		   build2_loc (loc, code, type, lhs, rhs));
+      return (!flag_permissive || ctx->quiet);
     }
   if (compare_tree_int (rhs, uprec) >= 0)
     {
       if (!ctx->quiet)
-	error_at (loc, "right operand of shift expression %q+E is >= than "
-		  "the precision of the left operand",
-		  build2_loc (loc, code, type, lhs, rhs));
-      return true;
+	permerror (loc, "right operand of shift expression %q+E is >= than "
+		   "the precision of the left operand",
+		   build2_loc (loc, code, type, lhs, rhs));
+      return (!flag_permissive || ctx->quiet);
     }
 
   /* The value of E1 << E2 is E1 left-shifted E2 bit positions; [...]
@@ -1536,9 +1536,10 @@ cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx,
       if (tree_int_cst_sgn (lhs) == -1)
 	{
 	  if (!ctx->quiet)
-	    error_at (loc, "left operand of shift expression %q+E is negative",
-		      build2_loc (loc, code, type, lhs, rhs));
-	  return true;
+	    permerror (loc,
+		       "left operand of shift expression %q+E is negative",
+		       build2_loc (loc, code, type, lhs, rhs));
+	  return (!flag_permissive || ctx->quiet);
 	}
       /* For signed x << y the following:
 	 (unsigned) x >> ((prec (lhs) - 1) - y)
@@ -1555,9 +1556,9 @@ cxx_eval_check_shift_p (location_t loc, const constexpr_ctx *ctx,
       if (tree_int_cst_lt (integer_one_node, t))
 	{
 	  if (!ctx->quiet)
-	    error_at (loc, "shift expression %q+E overflows",
-		      build2_loc (loc, code, type, lhs, rhs));
-	  return true;
+	    permerror (loc, "shift expression %q+E overflows",
+		       build2_loc (loc, code, type, lhs, rhs));
+	  return (!flag_permissive || ctx->quiet);
 	}
     }
   return false;
diff --git gcc/testsuite/g++.dg/warn/permissive-1.C gcc/testsuite/g++.dg/warn/permissive-1.C
index e69de29..bfaca76 100644
--- gcc/testsuite/g++.dg/warn/permissive-1.C
+++ gcc/testsuite/g++.dg/warn/permissive-1.C
@@ -0,0 +1,8 @@
+// PR c++/68979
+// { dg-do compile { target int32 } }
+// { dg-options "-fpermissive -Wno-shift-overflow -Wno-shift-count-overflow -Wno-shift-count-negative" }
+
+enum A { AA = -1 << 4 }; // { dg-warning "operand of shift expression" "" { target c++11 } }
+enum B { BB = 1 << -4 }; // { dg-warning "operand of shift expression" }
+enum C { CC = 1 << __SIZEOF_INT__ * 4 * __CHAR_BIT__ - 4 }; // { dg-warning "operand of shift expression" }
+enum D { DD = 10 << __SIZEOF_INT__ * __CHAR_BIT__ - 2 }; // { dg-warning "shift expression" "" { target c++11 } }

	Marek