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

[Frediano Ziglio]

> 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.
> 

No, once converted to indexes only indexes are used.

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

Do you mean test-codecs-parsing ?
 
> 
> >      if (video_codecs->len == 0) {
> >          spice_warning("Failed to set video codecs, input string: '%s'",
> >          codecs);

Frediano