c/2618: gcc crashes when doing _Bool = (unsigned char & 0x1) ?1 : 0

[Joseph S. Myers]

On 23 Apr 2001 cesarb@nitnet.com.br wrote:

> _Bool x;
> unsigned char y;
> 
> void fn(void)
> {
>         x = y & 0x1 ? 1 : 0;
> }

Fixed thus.  Bootstrapped against branch with no regressions on
i686-pc-linux-gnu; installed on mainline and branch.  (Note: the
included testcase shows that the bug is a regression from 2.95.)

2001-04-23  Joseph S. Myers  <jsm28@cam.ac.uk>

	* c-convert.c (convert): When converting to a BOOLEAN_TYPE, avoid
	passing nested NOP_EXPRs to fold.

2001-04-23  Joseph S. Myers  <jsm28@cam.ac.uk>

	* gcc.c-torture/compile/20010423-1.c: New test.

--- c-convert.c.orig	Mon Nov 13 14:10:46 2000
+++ c-convert.c	Mon Apr 23 22:07:52 2001
@@ -89,7 +89,15 @@ convert (type, expr)
   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
     return fold (convert_to_integer (type, e));
   if (code == BOOLEAN_TYPE)
-    return fold (build1 (NOP_EXPR, type, truthvalue_conversion (expr)));
+    {
+      tree t = truthvalue_conversion (expr);
+      /* If truthvalue_conversion returns a NOP_EXPR, we must fold it here
+	 to avoid infinite recursion between fold () and convert ().  */
+      if (TREE_CODE (t) == NOP_EXPR)
+	return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0)));
+      else
+	return fold (build1 (NOP_EXPR, type, t));
+    }
   if (code == POINTER_TYPE || code == REFERENCE_TYPE)
     return fold (convert_to_pointer (type, e));
   if (code == REAL_TYPE)
--- testsuite/gcc.c-torture/compile/20010423-1.c	Mon Mar 26 23:57:02 2001
+++ testsuite/gcc.c-torture/compile/20010423-1.c	Mon Apr 23 22:01:56 2001
@@ -0,0 +1,16 @@
+/* Origin: PR c/2618 from Cesar Eduardo Barros <cesarb@nitnet.com.br>,
+   adapted to a testcase by Joseph Myers <jsm28@cam.ac.uk>.
+
+   Boolean conversions were causing infinite recursion between convert
+   and fold in certain cases.  */
+
+#include <stdbool.h>
+
+bool x;
+unsigned char y;
+
+void
+fn (void)
+{
+  x = y & 0x1 ? 1 : 0;
+}

-- 
Joseph S. Myers
jsm28@cam.ac.uk