Re: [Qemu-devel] [PATCH v2 3/5] raw-posix: DPRINTF instead of DEBUG_BLOCK_PRINT

[Eric Blake]

On 05/08/2015 11:47 AM, Dimitris Aragiorgis wrote:
> Building the QEMU tools fails if we #define DEBUG_BLOCK inside
> block/raw-posix.c. Here instead of adding qemu-log.o in block-obj-y
> so that DEBUG_BLOCK_PRINT can be used, we substitute the latter with
> a simple DPRINTF().
> 
> Signed-off-by: Dimitris Aragiorgis <address@hidden>
> ---
>  block/raw-posix.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 24b061f..fbccca8 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -97,11 +97,11 @@
>  //#define DEBUG_FLOPPY
>  
>  //#define DEBUG_BLOCK
> -#if defined(DEBUG_BLOCK)
> -#define DEBUG_BLOCK_PRINT(formatCstr, ...) do { if (qemu_log_enabled()) \
> -    { qemu_log(formatCstr, ## __VA_ARGS__); qemu_log_flush(); } } while (0)
> +
> +#ifdef DEBUG_BLOCK
> +#define DPRINTF(fmt, ...) do { printf(fmt, ## __VA_ARGS__); } while (0)
>  #else
> -#define DEBUG_BLOCK_PRINT(formatCstr, ...)
> +#define DPRINTF(fmt, ...) do { } while (0)

Please fix this to ensure that we avoid bit-rot even when debugging is
not turned on.  Something like:

#ifdef DEBUG_BLOCK
# define DEBUG_BLOCK_PRINT 1
#else
# define DEBUG_BLOCK_PRINT 0
#endif
#define DPRINTF(fmt, ...) \
do \
    if (DEBUG_BLOCK_PRINT) { \
        printf(fmt, ## __VA_ARGS__); \
while (0)

that way, the compiler checks that the printf format arguments are valid
while still optimizing out the if(0) code.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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