Hi!
As discussed in the PR, on the following testcase we've regressed with the
introduction of c_fully_fold, when the C FE normally warns the argument
isn't folded yet. Fixed by also warning in c_fully_fold_internal, if before
that function the shift count wasn't INTEGER_CST and after it it is.
The testcase also revealed a regression on the C++ FE side, caused by
SIZEOF_EXPR folding deferral.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2013-01-08 Jakub Jelinek <ja...@redhat.com>
PR c/48418
* c-common.c (c_fully_fold_internal): Warn for LSHIFT_EXPR and
RSHIFT_EXPR, if orig_op1 isn't INTEGER_CST, op1 is INTEGER_CST
and is either negative or bigger or equal to type precision
of the first operand.
* typeck.c (cp_build_binary_op): For LSHIFT_EXPR and RSHIFT_EXPR,
call maybe_constant_value for the negative or too big shift
count warnings.
* c-c++-common/pr48418.c: New test.
--- gcc/c-family/c-common.c.jj 2012-12-31 15:05:45.000000000 +0100
+++ gcc/c-family/c-common.c 2013-01-08 15:15:47.019347593 +0100
@@ -1269,6 +1269,25 @@ c_fully_fold_internal (tree expr, bool i
&& !TREE_OVERFLOW_P (op0)
&& !TREE_OVERFLOW_P (op1))
overflow_warning (EXPR_LOCATION (expr), ret);
+ if ((code == LSHIFT_EXPR || code == RSHIFT_EXPR)
+ && TREE_CODE (orig_op1) != INTEGER_CST
+ && TREE_CODE (op1) == INTEGER_CST
+ && (TREE_CODE (TREE_TYPE (orig_op0)) == INTEGER_TYPE
+ || TREE_CODE (TREE_TYPE (orig_op0)) == FIXED_POINT_TYPE)
+ && TREE_CODE (TREE_TYPE (orig_op1)) == INTEGER_TYPE
+ && c_inhibit_evaluation_warnings == 0)
+ {
+ if (tree_int_cst_sgn (op1) < 0)
+ warning_at (loc, 0, (code == LSHIFT_EXPR
+ ? "left shift count is negative"
+ : "right shift count is negative"));
+ else if (compare_tree_int (op1,
+ TYPE_PRECISION (TREE_TYPE (orig_op0)))
+ >= 0)
+ warning_at (loc, 0, (code == LSHIFT_EXPR
+ ? "left shift count >= width of type"
+ : "right shift count >= width of type"));
+ }
goto out;
case INDIRECT_REF:
--- gcc/cp/typeck.c.jj 2013-01-07 14:14:44.000000000 +0100
+++ gcc/cp/typeck.c 2013-01-08 15:30:20.202388635 +0100
@@ -4095,10 +4095,13 @@ cp_build_binary_op (location_t location,
}
else if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
{
+ tree const_op1 = maybe_constant_value (op1);
+ if (TREE_CODE (const_op1) != INTEGER_CST)
+ const_op1 = op1;
result_type = type0;
- if (TREE_CODE (op1) == INTEGER_CST)
+ if (TREE_CODE (const_op1) == INTEGER_CST)
{
- if (tree_int_cst_lt (op1, integer_zero_node))
+ if (tree_int_cst_lt (const_op1, integer_zero_node))
{
if ((complain & tf_warning)
&& c_inhibit_evaluation_warnings == 0)
@@ -4106,7 +4109,7 @@ cp_build_binary_op (location_t location,
}
else
{
- if (compare_tree_int (op1, TYPE_PRECISION (type0)) >= 0
+ if (compare_tree_int (const_op1, TYPE_PRECISION (type0)) >= 0
&& (complain & tf_warning)
&& c_inhibit_evaluation_warnings == 0)
warning (0, "right shift count >= width of type");
@@ -4138,16 +4141,20 @@ cp_build_binary_op (location_t location,
}
else if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
{
+ tree const_op1 = maybe_constant_value (op1);
+ if (TREE_CODE (const_op1) != INTEGER_CST)
+ const_op1 = op1;
result_type = type0;
- if (TREE_CODE (op1) == INTEGER_CST)
+ if (TREE_CODE (const_op1) == INTEGER_CST)
{
- if (tree_int_cst_lt (op1, integer_zero_node))
+ if (tree_int_cst_lt (const_op1, integer_zero_node))
{
if ((complain & tf_warning)
&& c_inhibit_evaluation_warnings == 0)
warning (0, "left shift count is negative");
}
- else if (compare_tree_int (op1, TYPE_PRECISION (type0)) >= 0)
+ else if (compare_tree_int (const_op1,
+ TYPE_PRECISION (type0)) >= 0)
{
if ((complain & tf_warning)
&& c_inhibit_evaluation_warnings == 0)
--- gcc/testsuite/c-c++-common/pr48418.c.jj 2013-01-08 15:25:36.501003969
+0100
+++ gcc/testsuite/c-c++-common/pr48418.c 2013-01-08 15:21:54.000000000
+0100
@@ -0,0 +1,20 @@
+/* PR c/48418 */
+/* { dg-do compile } */
+/* { dg-options "-Wall -O2" } */
+
+int
+foo (int x)
+{
+ const int a = sizeof (int) * __CHAR_BIT__;
+ const int b = -7;
+ int c = 0;
+ c += x << a; /* { dg-warning "left shift count >=
width of type" } */
+ c += x << b; /* { dg-warning "left shift count is
negative" } */
+ c += x << (sizeof (int) * __CHAR_BIT__); /* { dg-warning "left shift count
>= width of type" } */
+ c += x << -7; /* { dg-warning "left shift
count is negative" } */
+ c += x >> a; /* { dg-warning "right shift count
>= width of type" } */
+ c += x >> b; /* { dg-warning "right shift count
is negative" } */
+ c += x >> (sizeof (int) * __CHAR_BIT__); /* { dg-warning "right shift count
>= width of type" } */
+ c += x >> -7; /* { dg-warning "right shift
count is negative" } */
+ return c;
+}
Jakub
