linux-kernel - RE: [PATCH] [ACPI] utilities/: Compliment va_start() with va

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Date:	Mon, 26 Nov 2007 14:14:47 -0800
From:	"Moore, Robert" <robert.moore@...el.com>
To:	"Len Brown" <lenb@...nel.org>
Cc:	<ricknu-0@...dent.ltu.se>, <linux-kernel@...r.kernel.org>,
	<linux-acpi@...r.kernel.org>
Subject: RE: [PATCH] [ACPI] utilities/: Compliment va_start() with va_end().

This is an interesting one to me.

>From various documentation:

After all arguments have been retrieved, va_end resets the pointer to
NULL.

va_end
Each invocation of va_start must be matched by a corresponding
invocation of va_end in the same function. After the call va_end(ap) the
variable ap is undefined. Multiple transversals of the list, each
bracketed by va_start and va_end are possible. va_end may be a macro or
a function.   

Now, I'm all for defensive programming, but I don't really see the point
of va_end when the list will be only traversed once.



We don't set all local pointers to NULL at function exit, what is the
point of doing it here?

I suppose some implementation could allocate memory at va_start, but in
practice, does this happen?

Bob


>-----Original Message-----
>From: Len Brown [mailto:lenb@...nel.org]
>Sent: Saturday, November 24, 2007 11:06 PM
>To: Moore, Robert
>Subject: Fwd: [PATCH] [ACPI] utilities/: Compliment va_start() with
>va_end().
>
>
>
>----------  Forwarded Message  ----------
>
>Subject: [PATCH] [ACPI] utilities/: Compliment va_start() with
va_end().
>Date: Saturday 24 November 2007 15:43
>From: Richard Knutsson <ricknu-0@...dent.ltu.se>
>To: len.brown@...el.com
>Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, Richard
>Knutsson <ricknu-0@...dent.ltu.se>
>
>Compliment va_start() with va_end().
>
>Signed-off-by: Richard Knutsson <ricknu-0@...dent.ltu.se>
>---
>Compile-tested on i386 with allyesconfig & allmodconfig.
>
> utdebug.c |    2 ++
> utmisc.c  |    4 ++++
> 2 files changed, 6 insertions(+)
>
>
>diff --git a/drivers/acpi/utilities/utdebug.c
>b/drivers/acpi/utilities/utdebug.c
>index c7e128e..f45e3d5 100644
>--- a/drivers/acpi/utilities/utdebug.c
>+++ b/drivers/acpi/utilities/utdebug.c
>@@ -203,6 +203,7 @@ acpi_ut_debug_print(u32 requested_debug_level,
>
> 	va_start(args, format);
> 	acpi_os_vprintf(format, args);
>+	va_end(args);
> }
>
> ACPI_EXPORT_SYMBOL(acpi_ut_debug_print)
>@@ -240,6 +241,7 @@ acpi_ut_debug_print_raw(u32 requested_debug_level,
>
> 	va_start(args, format);
> 	acpi_os_vprintf(format, args);
>+	va_end(args);
> }
>
> ACPI_EXPORT_SYMBOL(acpi_ut_debug_print_raw)
>diff --git a/drivers/acpi/utilities/utmisc.c
>b/drivers/acpi/utilities/utmisc.c
>index 2d19f71..ca4904c 100644
>--- a/drivers/acpi/utilities/utmisc.c
>+++ b/drivers/acpi/utilities/utmisc.c
>@@ -1032,6 +1032,7 @@ acpi_ut_error(char *module_name, u32 line_number,
>char *format, ...)
>
> 	va_start(args, format);
> 	acpi_os_vprintf(format, args);
>+	va_end(args);
> 	acpi_os_printf(" [%X]\n", ACPI_CA_VERSION);
> }
>
>@@ -1046,6 +1047,7 @@ acpi_ut_exception(char *module_name,
>
> 	va_start(args, format);
> 	acpi_os_vprintf(format, args);
>+	va_end(args);
> 	acpi_os_printf(" [%X]\n", ACPI_CA_VERSION);
> }
>
>@@ -1060,6 +1062,7 @@ acpi_ut_warning(char *module_name, u32
line_number,
>char *format, ...)
>
> 	va_start(args, format);
> 	acpi_os_vprintf(format, args);
>+	va_end(args);
> 	acpi_os_printf(" [%X]\n", ACPI_CA_VERSION);
> }
>
>@@ -1076,5 +1079,6 @@ acpi_ut_info(char *module_name, u32 line_number,
char
>*format, ...)
>
> 	va_start(args, format);
> 	acpi_os_vprintf(format, args);
>+	va_end(args);
> 	acpi_os_printf("\n");
> }
>-
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