avconv.c:3317: error: Uninitialized Value
  The value read from sync_stream_idx was never initialized.

avconv.c:3317:21: 
3315.                 if (sync_file_idx >= 0) {
3316.                     m->sync_file_index   = sync_file_idx;
3317.                     m->sync_stream_index = sync_stream_idx;
                          ^
3318.                 } else {
3319.                     m->sync_file_index   = file_idx;

static int opt_map(OptionsContext *o, const char *opt, const char *arg)
{
    StreamMap *m = NULL;
    int i, negative = 0, file_idx;
    int sync_file_idx = -1, sync_stream_idx;
    char *p, *sync;
    char *map;
    if (*arg == '-') {
        negative = 1;
        arg++;
    }
    map = av_strdup(arg);
    if (sync = strchr(map, ',')) {
        *sync = 0;
        sync_file_idx = strtol(sync + 1, &sync, 0);
        if (sync_file_idx >= nb_input_files || sync_file_idx < 0) {
            av_log(NULL, AV_LOG_FATAL, "Invalid sync file index: %d.\n", sync_file_idx);
            exit_program(1);
        }
        if (*sync)
            sync++;
        for (i = 0; i < input_files[sync_file_idx]->nb_streams; i++)
            if (check_stream_specifier(input_files[sync_file_idx]->ctx,
                                       input_files[sync_file_idx]->ctx->streams[i], sync) == 1) {
                sync_stream_idx = i;
                break;
            }
        if (i == input_files[sync_file_idx]->nb_streams) {
            av_log(NULL, AV_LOG_FATAL, "Sync stream specification in map %s does not "
                                       "match any streams.\n", arg);
            exit_program(1);
        }
    }
    if (map[0] == '[') {
        const char *c = map + 1;
        o->stream_maps = grow_array(o->stream_maps, sizeof(*o->stream_maps),
                                    &o->nb_stream_maps, o->nb_stream_maps + 1);
        m = &o->stream_maps[o->nb_stream_maps - 1];
        m->linklabel = av_get_token(&c, "]");
        if (!m->linklabel) {
            av_log(NULL, AV_LOG_ERROR, "Invalid output link label: %s.\n", map);
            exit_program(1);
        }
    } else {
        file_idx = strtol(map, &p, 0);
        if (file_idx >= nb_input_files || file_idx < 0) {
            av_log(NULL, AV_LOG_FATAL, "Invalid input file index: %d.\n", file_idx);
            exit_program(1);
        }
        if (negative)
            for (i = 0; i < o->nb_stream_maps; i++) {
                m = &o->stream_maps[i];
                if (file_idx == m->file_index &&
                    check_stream_specifier(input_files[m->file_index]->ctx,
                                           input_files[m->file_index]->ctx->streams[m->stream_index],
                                           *p == ':' ? p + 1 : p) > 0)
                    m->disabled = 1;
            }
        else
            for (i = 0; i < input_files[file_idx]->nb_streams; i++) {
                if (check_stream_specifier(input_files[file_idx]->ctx, input_files[file_idx]->ctx->streams[i],
                            *p == ':' ? p + 1 : p) <= 0)
                    continue;
                o->stream_maps = grow_array(o->stream_maps, sizeof(*o->stream_maps),
                                            &o->nb_stream_maps, o->nb_stream_maps + 1);
                m = &o->stream_maps[o->nb_stream_maps - 1];
                m->file_index   = file_idx;
                m->stream_index = i;
                if (sync_file_idx >= 0) {
                    m->sync_file_index   = sync_file_idx;
                    m->sync_stream_index = sync_stream_idx;
                } else {
                    m->sync_file_index   = file_idx;
                    m->sync_stream_index = i;
                }
            }
    }
    if (!m) {
        av_log(NULL, AV_LOG_FATAL, "Stream map '%s' matches no streams.\n", arg);
        exit_program(1);
    }
    av_freep(&map);
    return 0;
}
['static int opt_map(OptionsContext *o, const char *opt, const char *arg)\n{\n    StreamMap *m = NULL;\n    int i, negative = 0, file_idx;\n    int sync_file_idx = -1, sync_stream_idx;\n    char *p, *sync;\n    char *map;\n    if (*arg == \'-\') {\n        negative = 1;\n        arg++;\n    }\n    map = av_strdup(arg);\n    if (sync = strchr(map, \',\')) {\n        *sync = 0;\n        sync_file_idx = strtol(sync + 1, &sync, 0);\n        if (sync_file_idx >= nb_input_files || sync_file_idx < 0) {\n            av_log(NULL, AV_LOG_FATAL, "Invalid sync file index: %d.\\n", sync_file_idx);\n            exit_program(1);\n        }\n        if (*sync)\n            sync++;\n        for (i = 0; i < input_files[sync_file_idx]->nb_streams; i++)\n            if (check_stream_specifier(input_files[sync_file_idx]->ctx,\n                                       input_files[sync_file_idx]->ctx->streams[i], sync) == 1) {\n                sync_stream_idx = i;\n                break;\n            }\n        if (i == input_files[sync_file_idx]->nb_streams) {\n            av_log(NULL, AV_LOG_FATAL, "Sync stream specification in map %s does not "\n                                       "match any streams.\\n", arg);\n            exit_program(1);\n        }\n    }\n    if (map[0] == \'[\') {\n        const char *c = map + 1;\n        o->stream_maps = grow_array(o->stream_maps, sizeof(*o->stream_maps),\n                                    &o->nb_stream_maps, o->nb_stream_maps + 1);\n        m = &o->stream_maps[o->nb_stream_maps - 1];\n        m->linklabel = av_get_token(&c, "]");\n        if (!m->linklabel) {\n            av_log(NULL, AV_LOG_ERROR, "Invalid output link label: %s.\\n", map);\n            exit_program(1);\n        }\n    } else {\n        file_idx = strtol(map, &p, 0);\n        if (file_idx >= nb_input_files || file_idx < 0) {\n            av_log(NULL, AV_LOG_FATAL, "Invalid input file index: %d.\\n", file_idx);\n            exit_program(1);\n        }\n        if (negative)\n            for (i = 0; i < o->nb_stream_maps; i++) {\n                m = &o->stream_maps[i];\n                if (file_idx == m->file_index &&\n                    check_stream_specifier(input_files[m->file_index]->ctx,\n                                           input_files[m->file_index]->ctx->streams[m->stream_index],\n                                           *p == \':\' ? p + 1 : p) > 0)\n                    m->disabled = 1;\n            }\n        else\n            for (i = 0; i < input_files[file_idx]->nb_streams; i++) {\n                if (check_stream_specifier(input_files[file_idx]->ctx, input_files[file_idx]->ctx->streams[i],\n                            *p == \':\' ? p + 1 : p) <= 0)\n                    continue;\n                o->stream_maps = grow_array(o->stream_maps, sizeof(*o->stream_maps),\n                                            &o->nb_stream_maps, o->nb_stream_maps + 1);\n                m = &o->stream_maps[o->nb_stream_maps - 1];\n                m->file_index   = file_idx;\n                m->stream_index = i;\n                if (sync_file_idx >= 0) {\n                    m->sync_file_index   = sync_file_idx;\n                    m->sync_stream_index = sync_stream_idx;\n                } else {\n                    m->sync_file_index   = file_idx;\n                    m->sync_stream_index = i;\n                }\n            }\n    }\n    if (!m) {\n        av_log(NULL, AV_LOG_FATAL, "Stream map \'%s\' matches no streams.\\n", arg);\n        exit_program(1);\n    }\n    av_freep(&map);\n    return 0;\n}']