[Mesa-dev] [PATCH shader-db 3/3] run: add extension_in_string() helper

[Matt Turner]

On Mon, Aug 21, 2017 at 3:27 AM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> From: Emil Velikov <emil.velikov at collabora.com>
>
> memmem() does not attribute what the character after the searched string
> is. Thus it will flag even when haystack is "foobar" while we're looking
> for "foo".
>
> Pull a small helper (based on piglit) that correctly handles this and use
> it.
>
> Note: when parsing through the shader we have a non-zero terminated
> needle, let's keep the memmem in there for now.
>
> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> ---
>  run.c | 43 +++++++++++++++++++++++++++++++++++--------
>  1 file changed, 35 insertions(+), 8 deletions(-)
>
> diff --git a/run.c b/run.c
> index d0d4598..0691d33 100644
> --- a/run.c
> +++ b/run.c
> @@ -69,6 +69,35 @@ struct shader {
>      int type;
>  };
>
> +static bool
> +extension_in_string(const char *haystack, const char *needle)
> +{
> +    const unsigned needle_len = strlen(needle);
> +
> +    if (needle_len == 0)
> +        return false;
> +
> +    while (true) {
> +        const char *const s = strstr(haystack, needle);
> +
> +        if (s == NULL)
> +            return false;
> +
> +        if (s[needle_len] == ' ' || s[needle_len] == '\0')
> +            return true;
> +
> +        /* strstr found an extension whose name begins with
> +         * needle, but whose name is not equal to needle.
> +         * Restart the search at s + needle_len so that we
> +         * don't just find the same extension again and go
> +         * into an infinite loop.
> +         */
> +        haystack = s + needle_len;
> +    }
> +
> +    return false;
> +}
> +
>  static struct shader *
>  get_shaders(const struct context_info *core, const struct context_info *compat,
>              const char *text, size_t text_size,
> @@ -141,8 +170,8 @@ get_shaders(const struct context_info *core, const struct context_info *compat,
>          extension_text += 1;
>          const char *newline = memchr(extension_text, '\n',
>                                       end_text - extension_text);
> -        if (memmem(info->extension_string, info->extension_string_len,
> -                   extension_text, newline - extension_text) == NULL) {
> +        if (memmem(info->extension_string, info->extension_string_len,
> +                   extension_text, newline - extension_text) == NULL) {
>              fprintf(stderr, "SKIP: %s requires unavailable extension %.*s\n",
>                      shader_name, (int)(newline - extension_text), extension_text);
>              return NULL;
> @@ -415,7 +444,7 @@ main(int argc, char **argv)
>          return -1;
>      }
>
> -    if (!strstr(client_extensions, "EGL_MESA_platform_gbm")) {
> +    if (!extension_in_string(client_extensions, "EGL_MESA_platform_gbm")) {
>          fprintf(stderr, "ERROR: Missing EGL_MESA_platform_gbm\n");
>          return -1;
>      }
> @@ -458,7 +487,7 @@ main(int argc, char **argv)
>      };
>      for (int i = 0; i < ARRAY_SIZE(egl_extension); i++) {
>          const char *extension_string = eglQueryString(egl_dpy, EGL_EXTENSIONS);
> -        if (strstr(extension_string, egl_extension[i]) == NULL) {
> +        if (!extension_in_string(extension_string, egl_extension[i])) {
>              fprintf(stderr, "ERROR: Missing %s\n", egl_extension[i]);
>              ret = -1;
>              goto egl_terminate;
> @@ -530,8 +559,7 @@ main(int argc, char **argv)
>
>          core.max_glsl_version = get_glsl_version();
>
> -        if (memmem(core.extension_string, core.extension_string_len,
> -                   "GL_KHR_debug", strlen("GL_KHR_debug")) == NULL) {
> +        if (!extension_in_string(core.extension_string, "GL_KHR_debug")) {

I don't know what happened between this patch and getting committed,
but what was committed contained a copy-and-paste mistake here (used
compat.extension_string, which is NULL rather than
core.extension_string) so run always segfaulted!

I pushed a fix. Kind of irritating that this wasn't fixed in the week
since it was reported.