On Fri, 2006-10-13 at 12:59 +0100, Catalin Marinas wrote:
> On 13/10/06, Pekka Enberg <[email protected]> wrote:
> > On 10/13/06, [email protected] <[email protected]> wrote:
> > > If anyone has a version of kmemleak that I can build with 4.1.1, or
> > > any other suggestions for instrumentation, I'd be happy to gather more
> > > data - the problem is very easy for me to reproduce.
> >
> > You should cc Catalin for that. Alternatively, you could try
> > CONFIG_DEBUG_SLAB_LEAK.
>
> Thanks for cc'ing me (I'm still on holiday and not following the
> mailing list). The problem is the __builtin_constant_p gcc function
> which doesn't work properly with 4.x versions. It was fixed in latest
> gcc versions though. Kmemleak relies on __builtin_constant_p to
> determine the pointer aliases and without it you would get plenty of
> false positives.
SuSE (for one?) doesn't appear to know about it. gcc version 4.1.2
20060920 (month old prerelease) still has the problem. After some
rummaging around, I found the fix (attached in case someone else wants
to try it).
2.6.19-rc1 + patch-2.6.19-rc1-kmemleak-0.11 compiles fine now (unless
CONFIG_DEBUG_KEEP_INIT is set), boots and runs too.. but axle grease
runs a lot faster ;-) I'll try a stripped down config sometime.
-Mike
2006-06-04 Mark Shinwell <shinwell codesourcery com>
* tree.h: Declare folding_initializer.
* builtins.c (fold_builtin_constant_p): Give definite answer
if folding inside an initializer.
* fold-const.c: Define folding_initializer.
(START_FOLD_INIT): Save and then set folding_initializer.
(END_FOLD_INIT): Restore folding_initializer.
* gcc.c-torture/compile/builtin_constant_p.c: New test.
--- gcc/tree.h (revision 114357)
+++ gcc/tree.h (revision 114359)
@@ -4142,6 +4142,10 @@ extern void using_eh_for_cleanups (void)
/* In fold-const.c */
+/* Non-zero if we are folding constants inside an initializer; zero
+ otherwise. */
+extern int folding_initializer;
+
/* Fold constants as much as possible in an expression.
Returns the simplified expression.
Acts only on the top level of the expression;
--- gcc/builtins.c (revision 114357)
+++ gcc/builtins.c (revision 114359)
@@ -6495,7 +6495,8 @@ fold_builtin_constant_p (tree arglist)
if (TREE_SIDE_EFFECTS (arglist)
|| AGGREGATE_TYPE_P (TREE_TYPE (arglist))
|| POINTER_TYPE_P (TREE_TYPE (arglist))
- || cfun == 0)
+ || cfun == 0
+ || folding_initializer)
return integer_zero_node;
return 0;
--- gcc/fold-const.c (revision 114357)
+++ gcc/fold-const.c (revision 114359)
@@ -59,6 +59,10 @@ Software Foundation, 51 Franklin Street,
#include "langhooks.h"
#include "md5.h"
+/* Non-zero if we are folding constants inside an initializer; zero
+ otherwise. */
+int folding_initializer = 0;
+
/* The following constants represent a bit based encoding of GCC's
comparison operators. This encoding simplifies transformations
on relational comparison operators, such as AND and OR. */
@@ -11708,16 +11712,19 @@ fold_build3_stat (enum tree_code code, t
int saved_trapping_math = flag_trapping_math;\
int saved_rounding_math = flag_rounding_math;\
int saved_trapv = flag_trapv;\
+ int saved_folding_initializer = folding_initializer;\
flag_signaling_nans = 0;\
flag_trapping_math = 0;\
flag_rounding_math = 0;\
- flag_trapv = 0
+ flag_trapv = 0;\
+ folding_initializer = 1;
#define END_FOLD_INIT \
flag_signaling_nans = saved_signaling_nans;\
flag_trapping_math = saved_trapping_math;\
flag_rounding_math = saved_rounding_math;\
- flag_trapv = saved_trapv
+ flag_trapv = saved_trapv;\
+ folding_initializer = saved_folding_initializer;
tree
fold_build1_initializer (enum tree_code code, tree type, tree op)
--- gcc/testsuite/gcc.c-torture/compile/builtin_constant_p.c (revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/builtin_constant_p.c (revision 114359)
@@ -0,0 +1,8 @@
+/* { dg-options "-O2" } */
+
+int main (int argc, char *argv[])
+{
+ static int a[] = { __builtin_constant_p (argc) ? 1 : 0 };
+ return a[0];
+}
+
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