Re: [PATCH] log: Avoid time_t/__syscall_slong_t format mismatch with long int on X32 ABI

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Mar 13, 2023 at 01:07:15PM +0100, Stefano Brivio wrote:
> On X32 (ILP32 using AMD64 system call ABI) and glibc,
> struct timespec::tv_nsec is __syscall_slong_t and not a long int, see
> also https://sourceware.org/bugzilla/show_bug.cgi?id=16437 and
> timespec(3type). Fine, we could cast that down to long and be done
> with it.
> 
> But it turns out that also time_t (not guaranteed to be equivalent to
> any type) is a long long int, and there we can't downcast.
> 
> To keep it simple, cast both to long long int, and change formats to
> %lli, to avoid format warnings from gcc.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  log.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/log.c b/log.c
> index d2f08fa..d7411ba 100644
> --- a/log.c
> +++ b/log.c
> @@ -53,9 +53,9 @@ void name(const char *format, ...) {					\
>  									\
>  	if (setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) {	\
>  		clock_gettime(CLOCK_REALTIME, &tp);			\
> -		fprintf(stderr, "%li.%04li: ",				\
> -			tp.tv_sec - log_start,				\
> -			tp.tv_nsec / (100L * 1000));			\
> +		fprintf(stderr, "%lli.%04lli: ",			\
> +			(long long int)tp.tv_sec - log_start,		\
> +			(long long int)tp.tv_nsec / (100L * 1000));	\
>  	}								\
>  									\
>  	if ((LOG_MASK(LOG_PRI(level)) & log_mask) || BEFORE_DAEMON) {	\
> @@ -225,8 +225,9 @@ static void logfile_rotate_fallocate(int fd, struct timespec *ts)
>  		return;
>  
>  	n = snprintf(buf, BUFSIZ,
> -		     "%s - log truncated at %li.%04li", log_header,
> -		     ts->tv_sec - log_start, ts->tv_nsec / (100L * 1000));
> +		     "%s - log truncated at %lli.%04lli", log_header,
> +		     (long long int)(ts->tv_sec - log_start),
> +		     (long long int)(ts->tv_nsec / (100L * 1000)));
>  
>  	/* Avoid partial lines by padding the header with spaces */
>  	nl = memchr(buf + n + 1, '\n', BUFSIZ - n - 1);
> @@ -256,9 +257,9 @@ static void logfile_rotate_move(int fd, struct timespec *ts)
>  	char buf[BUFSIZ], *nl;
>  
>  	header_len = snprintf(buf, BUFSIZ,
> -			      "%s - log truncated at %li.%04li\n", log_header,
> -			      ts->tv_sec - log_start,
> -			      ts->tv_nsec / (100L * 1000));
> +			      "%s - log truncated at %lli.%04lli\n", log_header,
> +			      (long long int)(ts->tv_sec - log_start),
> +			      (long long int)(ts->tv_nsec / (100L * 1000)));
>  	if (lseek(fd, 0, SEEK_SET) == -1)
>  		return;
>  	if (write(fd, buf, header_len) == -1)
> @@ -349,8 +350,9 @@ void logfile_write(int pri, const char *format, va_list ap)
>  	if (clock_gettime(CLOCK_REALTIME, &ts))
>  		return;
>  
> -	n = snprintf(buf, BUFSIZ, "%li.%04li: %s",
> -		     ts.tv_sec - log_start, ts.tv_nsec / (100L * 1000),
> +	n = snprintf(buf, BUFSIZ, "%lli.%04lli: %s",
> +		     (long long int)(ts.tv_sec - log_start),
> +		     (long long int)(ts.tv_nsec / (100L * 1000)),
>  		     logfile_prefix[pri]);
>  
>  	n += vsnprintf(buf + n, BUFSIZ - n, format, ap);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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