linux-kernel - [PATCH] FRV: Work around a possible compiler bug

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Date:	Wed, 18 Jul 2007 14:02:33 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...l.org
Cc:	linux-kernel@...r.kernel.org, dhowells@...hat.com
Subject: [PATCH] FRV: Work around a possible compiler bug

From: David Howells <dhowells@...hat.com>

Work around a possible bug in the FRV compiler.

What appears to be happening is that gcc resolves the __builtin_constant_p()
in kmalloc() to true, but then fails to reduce the therefore constant
conditions in the if-statements it guards to constant results.

When compiling with -O2 or -Os, one single spurious error crops up in
cpuup_callback() in mm/slab.c.  This can be avoided by making the memsize
variable const.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 arch/frv/Makefile |    2 +-
 mm/slab.c         |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/frv/Makefile b/arch/frv/Makefile
index 038e3a8..9bf7345 100644
--- a/arch/frv/Makefile
+++ b/arch/frv/Makefile
@@ -88,7 +88,7 @@ ASFLAGS		+= -mno-fdpic
 # make sure the .S files get compiled with debug info
 # and disable optimisations that are unhelpful whilst debugging
 ifdef CONFIG_DEBUG_INFO
-CFLAGS		+= -O1
+#CFLAGS		+= -O1
 AFLAGS		+= -Wa,--gdwarf2
 ASFLAGS		+= -Wa,--gdwarf2
 endif
diff --git a/mm/slab.c b/mm/slab.c
index 96d30ee..88bc633 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1163,7 +1163,7 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
 	struct kmem_cache *cachep;
 	struct kmem_list3 *l3 = NULL;
 	int node = cpu_to_node(cpu);
-	int memsize = sizeof(struct kmem_list3);
+	const int memsize = sizeof(struct kmem_list3);
 
 	switch (action) {
 	case CPU_LOCK_ACQUIRE:

-
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