Currently the C FE's -Wdiv-by-zero warns only for INTEGER_CSTs,
unlike C++, which can also handle const ints (yes, different
constant expression rules). But since it's easy to warn for
consts in the C FE as well, and we already warn for shifts
with const ints, I think we can go with the following. The PR
is a request for this.
Bootstrapped/regtested on {x86_64,ppc64}-linux, ok for trunk?
2015-01-06 Marek Polacek pola...@redhat.com
PR c/64440
* c-common.c (c_fully_fold_internal): Warn for division and modulo
if orig_op1 isn't INTEGER_CST, op1 is INTEGER_CST and is zero.
* gcc.dg/pr64440.c: New test.
* c-c++-common/pr56607.c: Don't limit dg-warnings to C++.
diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index 4d9dd4d..df4fddd 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -1364,6 +1364,17 @@ c_fully_fold_internal (tree expr, bool in_init, bool
*maybe_const_operands,
? G_(left shift count = width of type)
: G_(right shift count = width of type)));
}
+ if ((code == TRUNC_DIV_EXPR
+ || code == CEIL_DIV_EXPR
+ || code == FLOOR_DIV_EXPR
+ || code == EXACT_DIV_EXPR
+ || code == TRUNC_MOD_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)
+ warn_for_div_by_zero (loc, op1);
goto out;
case INDIRECT_REF:
diff --git gcc/testsuite/c-c++-common/pr56607.c
gcc/testsuite/c-c++-common/pr56607.c
index d7faa81..ba13956 100644
--- gcc/testsuite/c-c++-common/pr56607.c
+++ gcc/testsuite/c-c++-common/pr56607.c
@@ -12,7 +12,7 @@ int
f2 (void)
{
const int x = sizeof (char) - 1;
- return 1 / x;/* { dg-warning division by
zero { target c++ } } */
+ return 1 / x;/* { dg-warning division by
zero } */
}
int
@@ -25,5 +25,5 @@ int
f4 (void)
{
const int x = sizeof (int) / 3 - 1;
- return 1 / x;/* { dg-warning division by
zero { target c++ } } */
+ return 1 / x;/* { dg-warning division by
zero } */
}
diff --git gcc/testsuite/gcc.dg/pr64440.c gcc/testsuite/gcc.dg/pr64440.c
index e69de29..f9cc46d 100644
--- gcc/testsuite/gcc.dg/pr64440.c
+++ gcc/testsuite/gcc.dg/pr64440.c
@@ -0,0 +1,15 @@
+/* PR c/64440 */
+/* { dg-do compile } */
+/* { dg-options -Wall -O2 } */
+
+int
+foo (int x)
+{
+ const int y = 0;
+ int r = 0;
+ r += x / y; /* { dg-warning division by zero } */
+ r += x / 0; /* { dg-warning division by zero } */
+ r += x % y; /* { dg-warning division by zero } */
+ r += x % 0; /* { dg-warning division by zero } */
+ return r;
+}
Marek
