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[RFA] Close PR 150: division by zero
- To: gcc-patches at gcc dot gnu dot org
- Subject: [RFA] Close PR 150: division by zero
- From: Neil Booth <neil at daikokuya dot demon dot co dot uk>
- Date: Sun, 21 Oct 2001 21:28:45 +0100
This simple patch + testcase closes PR 150, which is a request to warn
about compile-time division by zero, which can appear in non-obvious
ways from e.g. macros.
Bootstrapped x86 Linux, no regressions. OK to commit?
Neil.
* c-typeck.c (build_binary_op): Warn about division by zero.
* testsuite/gcc.dg/divbyzero.c: New test.
* testsuite/gcc.dg/noncompile/20010524-1.c: Update.
Index: c-typeck.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-typeck.c,v
retrieving revision 1.141
diff -u -p -r1.141 c-typeck.c
--- c-typeck.c 2001/10/11 03:15:23 1.141
+++ c-typeck.c 2001/10/21 20:21:54
@@ -1973,6 +1973,9 @@ build_binary_op (code, orig_op0, orig_op
case FLOOR_DIV_EXPR:
case ROUND_DIV_EXPR:
case EXACT_DIV_EXPR:
+ if (integer_zerop (op1) || real_zerop (op1))
+ warning ("division by zero");
+
if ((code0 == INTEGER_TYPE || code0 == REAL_TYPE
|| code0 == COMPLEX_TYPE)
&& (code1 == INTEGER_TYPE || code1 == REAL_TYPE
@@ -2026,6 +2029,9 @@ build_binary_op (code, orig_op0, orig_op
case TRUNC_MOD_EXPR:
case FLOOR_MOD_EXPR:
+ if (integer_zerop (op1))
+ warning ("division by zero");
+
if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
{
/* Although it would be tempting to shorten always here, that loses
Index: testsuite/gcc.dg/divbyzero.c
===================================================================
RCS file: divbyzero.c
diff -N divbyzero.c
--- /dev/null Tue May 5 13:32:27 1998
+++ divbyzero.c Sun Oct 21 13:21:54 2001
@@ -0,0 +1,19 @@
+/* Copyright (C) 2001 Free Software Foundation, Inc. */
+
+/* { dg-do compile } */
+
+/* Source: Neil Booth, Oct 21 2001. PR 150 - warn about division by
+ zero. */
+
+#define ZERO (4 - 6 + 2)
+#define DZERO (2.0 - 2.0)
+
+int main (int argc, char *argv[])
+{
+ int w = argc % ZERO; /* { dg-warning "division by zero" } */
+ int x = argc / 0; /* { dg-warning "division by zero" } */
+ int y = argc / ZERO; /* { dg-warning "division by zero" } */
+ double z = argc / DZERO; /* { dg-warning "division by zero" } */
+
+ return 0;
+}
Index: testsuite/gcc.dg/noncompile/20010524-1.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/testsuite/gcc.dg/noncompile/20010524-1.c,v
retrieving revision 1.2
diff -u -p -r1.2 20010524-1.c
--- 20010524-1.c 2001/05/25 06:34:16 1.2
+++ 20010524-1.c 2001/10/21 20:21:54
@@ -1,2 +1,2 @@
int i = 7 / 0; /* { dg-error "not constant" } */
-
+ /* { dg-warning "division by zero" "div by zero" { target *-*-* } 1 } */