Re: [PATCH v2 09/13] util/hexdump: Replace sprintf() by g_string_append_printf()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 11/4/24 12:15, Philippe Mathieu-Daudé wrote:
> sprintf() is deprecated on Darwin since macOS 13.0 / XCode 14.1,
> resulting in painful developper experience.
> 
> Replace sprintf() by GString API in order to avoid:
> 
>    [426/1310] Compiling C object libqemuutil.a.p/util_hexdump.c.o
>    util/hexdump.c:35:21: warning: 'sprintf' is deprecated:
>      This function is provided for compatibility reasons only.
>      Due to security concerns inherent in the design of sprintf(3),
>      it is highly recommended that you use snprintf(3) instead.
>      [-Wdeprecated-declarations]
>              line += sprintf(line, " %02x", (unsigned char)buf[b + i]);
>                      ^
>    util/hexdump.c:37:21: warning: 'sprintf' is deprecated:
>              line += sprintf(line, "   ");
>                      ^
>    2 warnings generated.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   util/hexdump.c | 17 ++++++++---------
>   1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/util/hexdump.c b/util/hexdump.c
> index b6f70e93bb..2ec1171de3 100644
> --- a/util/hexdump.c
> +++ b/util/hexdump.c
> @@ -19,7 +19,7 @@
>   char *qemu_hexdump_line(const void *bufptr, unsigned offset,
>                           unsigned int len, bool ascii)
>   {
> -    char linebuf[QEMU_HEXDUMP_LINE_BYTES], *line = linebuf;
> +    g_autoptr(GString) gs = g_string_sized_new(QEMU_HEXDUMP_LINE_BYTES);
>       const char *buf = bufptr;
>       int i, c;
>   
> @@ -27,30 +27,29 @@ char *qemu_hexdump_line(const void *bufptr, unsigned offset,
>           len = QEMU_HEXDUMP_LINE_BYTES;
>       }
>   
> -    line += snprintf(line, 6, "%04x:", offset);
> +    g_string_append_printf(gs, "%04x:", offset);
>       for (i = 0; i < QEMU_HEXDUMP_LINE_BYTES; i++) {
>           if ((i % 4) == 0) {
> -            *line++ = ' ';
> +            g_string_append_c(gs, ' ');
>           }
>           if (i < len) {
> -            line += sprintf(line, " %02x", (unsigned char)buf[offset + i]);
> +            g_string_append_printf(gs, " %02x", (unsigned char)buf[offset + i]);

I find using g_string_append_printf() simpler than checking snprintf()
return value, and don't expect this function to be in hot path, but if
preferred I can try to not use the GString API.

>           } else {
> -            line += sprintf(line, "   ");
> +            g_string_append(gs, "   ");
>           }
>       }