[Spice-devel] [PATCH spice-server v4 03/20] Avoids %m in formatting for Windows

[Marc-André Lureau]

Hi

On Wed, Feb 6, 2019 at 2:59 PM Frediano Ziglio <fziglio at redhat.com> wrote:
>
> Not supported, %m is a GNU extension of sscanf.
>
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> ---
>  server/reds.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/server/reds.c b/server/reds.c
> index d3f73d8e..8c1c10dc 100644
> --- a/server/reds.c
> +++ b/server/reds.c
> @@ -3698,8 +3698,7 @@ static const int video_codec_caps[] = {
>   * @codec: a location to return the parsed codec
>   * @return the position of the next codec in the string
>   */
> -static const char* parse_next_video_codec(const char *codecs, char **encoder,
> -                                          char **codec)
> +static char* parse_next_video_codec(char *codecs, char **encoder, char **codec)
>  {
>      if (!codecs) {
>          return NULL;
> @@ -3708,14 +3707,15 @@ static const char* parse_next_video_codec(const char *codecs, char **encoder,
>      if (!*codecs) {
>          return NULL;
>      }
> -    int n;
> +    int end_encoder, end_codec = -1;
>      *encoder = *codec = NULL;
> -    if (sscanf(codecs, "%m[0-9a-zA-Z_]:%m[0-9a-zA-Z_]%n", encoder, codec, &n) == 2) {
> -        // this avoids accepting "encoder:codec" followed by garbage like "$%*"
> -        if (codecs[n] != ';' && codecs[n] != '\0') {
> -            free(*codec);
> -            *codec = NULL;
> -        }
> +    if (sscanf(codecs, "%*[0-9a-zA-Z_]:%n%*[0-9a-zA-Z_];%n", &end_encoder, &end_codec) == 0
> +        && end_codec > 0) {
> +        codecs[end_encoder - 1] = '\0';
> +        codecs[end_codec - 1] = '\0';
> +        *encoder = codecs;
> +        *codec = codecs + end_encoder;
> +        return codecs + end_codec;
>      }
>      return codecs + strcspn(codecs, ";");
>  }
> @@ -3732,7 +3732,8 @@ static void reds_set_video_codecs_from_string(RedsState *reds, const char *codec
>      }
>
>      video_codecs = g_array_new(FALSE, FALSE, sizeof(RedVideoCodec));
> -    const char *c = codecs;
> +    char *codecs_copy = g_strdup_printf("%s;", codecs);
> +    char *c = codecs_copy;
>      while ( (c = parse_next_video_codec(c, &encoder_name, &codec_name)) ) {
>          uint32_t encoder_index, codec_index;
>          if (!encoder_name || !codec_name) {
> @@ -3755,11 +3756,9 @@ static void reds_set_video_codecs_from_string(RedsState *reds, const char *codec
>              g_array_append_val(video_codecs, new_codec);
>          }
>
> -        /* these are allocated by sscanf, do not use g_free */
> -        free(encoder_name);
> -        free(codec_name);
>          codecs = c;
>      }
> +    g_free(codecs_copy);
>

codecs may refer to free memory after this, I believe.

Would be nice to factor this parsing code out of RedsState and make
some unit tests.


>      if (video_codecs->len == 0) {
>          spice_warning("Failed to set video codecs, input string: '%s'", codecs);
> --
> 2.20.1
>
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-- 
Marc-André Lureau