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Subject[PATCH 10/36] driver core: Convert debug functions declared inline __attribute__((format (printf,x,y) to statement expression macros
Date
From: Joe Perches <joe@perches.com>

When DEBUG is not defined, pr_debug and dev_dbg and some
other local debugging functions are specified as:

"inline __attribute__((format (printf, x, y)))"

This is done to validate printk arguments when not debugging.

Converting these functions to macros or statement expressions
"do { if (0) printk(fmt, ##arg); } while (0)"
or
"({ if (0) printk(fmt, ##arg); 0; })
makes at least gcc 4.2.2 produce smaller objects.

This has the additional benefit of allowing the optimizer to
avoid calling functions like print_mac that might have been
arguments to the printk.

defconfig x86 current:

$ size vmlinux
text data bss dec hex filename
4716770 474560 618496 5809826 58a6a2 vmlinux

all converted: (More patches follow)

$ size vmlinux
text data bss dec hex filename
4716642 474560 618496 5809698 58a622 vmlinux

Even kernel/sched.o, which doesn't even use these
functions, becomes smaller.

It appears that merely having an indirect include
of <linux/device.h> can cause bigger objects.

$ size sched.inline.o sched.if0.o
text data bss dec hex filename
31385 2854 328 34567 8707 sched.inline.o
31366 2854 328 34548 86f4 sched.if0.o

The current preprocessed only kernel/sched.i file contains:

# 612 "include/linux/device.h"
static inline __attribute__((always_inline)) int __attribute__ ((format (printf, 2, 3)))
dev_dbg(struct device *dev, const char *fmt, ...)
{
return 0;
}
# 628 "include/linux/device.h"
static inline __attribute__((always_inline)) int __attribute__ ((format (printf, 2, 3)))
dev_vdbg(struct device *dev, const char *fmt, ...)
{
return 0;
}

Removing these unused inlines from sched.i shrinks sched.o

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
include/linux/device.h | 15 +++++----------
include/linux/kernel.h | 6 ++----
2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index 2258d89..d576611 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -608,21 +608,16 @@ extern const char *dev_driver_string(struct device *dev);
#define dev_dbg(dev, format, arg...) \
dev_printk(KERN_DEBUG , dev , format , ## arg)
#else
-static inline int __attribute__ ((format (printf, 2, 3)))
-dev_dbg(struct device *dev, const char *fmt, ...)
-{
- return 0;
-}
+#define dev_dbg(dev, format, arg...) \
+ ({ if (0) dev_printk(KERN_DEBUG, dev, format, ##arg); 0; })
#endif

#ifdef VERBOSE_DEBUG
#define dev_vdbg dev_dbg
#else
-static inline int __attribute__ ((format (printf, 2, 3)))
-dev_vdbg(struct device *dev, const char *fmt, ...)
-{
- return 0;
-}
+
+#define dev_vdbg(dev, format, arg...) \
+ ({ if (0) dev_printk(KERN_DEBUG, dev, format, ##arg); 0; })
#endif

/* Create alias, so I can be autoloaded. */
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2df44e7..cd6d02c 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -293,10 +293,8 @@ extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
#define pr_debug(fmt, arg...) \
printk(KERN_DEBUG fmt, ##arg)
#else
-static inline int __attribute__ ((format (printf, 1, 2))) pr_debug(const char * fmt, ...)
-{
- return 0;
-}
+#define pr_debug(fmt, arg...) \
+ ({ if (0) printk(KERN_DEBUG fmt, ##arg); 0; })
#endif

/*
--
1.5.4.5


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