[Mesa-dev] [PATCH] mesa: if MESA_DEBUG=context, create a debug context

[Nicolai Hähnle]

On 16.11.2016 00:05, Brian Paul wrote:
> A number of drivers report useful debug/perf information accessible
> through GL_ARB_debug_output and with debug contexts (i.e. setting the
> GLX_CONTEXT_DEBUG_BIT_ARB flag).  But few applications actually use
> the GL_ARB_debug_output extension.
>
> This change lets one set the MESA_DEBUG env var to "context" to force-set
> a debug context and report debug/perf messages to stderr (or whatever
> file MESA_LOG_FILE is set to).  This is a useful debugging tool.
>
> The small change in st_api_create_context() is needed so that
> st_update_debug_callback() gets called to hook up the driver debug
> callbacks when ST_CONTEXT_FLAG_DEBUG was not set, but MESA_DEBUG=context.
> ---
>  src/mesa/main/debug.c               |  3 ++-
>  src/mesa/main/debug_output.c        | 28 ++++++++++++++++++++++++++++
>  src/mesa/main/mtypes.h              |  3 ++-
>  src/mesa/state_tracker/st_manager.c |  2 ++
>  4 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/main/debug.c b/src/mesa/main/debug.c
> index 5ca7d5c..3471b26 100644
> --- a/src/mesa/main/debug.c
> +++ b/src/mesa/main/debug.c
> @@ -189,7 +189,8 @@ set_debug_flags(const char *str)
>        { "silent", DEBUG_SILENT }, /* turn off debug messages */
>        { "flush", DEBUG_ALWAYS_FLUSH }, /* flush after each drawing command */
>        { "incomplete_tex", DEBUG_INCOMPLETE_TEXTURE },
> -      { "incomplete_fbo", DEBUG_INCOMPLETE_FBO }
> +      { "incomplete_fbo", DEBUG_INCOMPLETE_FBO },
> +      { "context", DEBUG_CONTEXT } /* force set GL_CONTEXT_FLAG_DEBUG_BIT flag */
>     };
>     GLuint i;
>
> diff --git a/src/mesa/main/debug_output.c b/src/mesa/main/debug_output.c
> index 85f64bd..290d626 100644
> --- a/src/mesa/main/debug_output.c
> +++ b/src/mesa/main/debug_output.c
> @@ -99,6 +99,7 @@ struct gl_debug_state
>     const void *CallbackData;
>     GLboolean SyncOutput;
>     GLboolean DebugOutput;
> +   GLboolean LogToStderr;
>
>     struct gl_debug_group *Groups[MAX_DEBUG_GROUP_STACK_DEPTH];
>     struct gl_debug_message GroupMessages[MAX_DEBUG_GROUP_STACK_DEPTH];
> @@ -617,6 +618,17 @@ debug_log_message(struct gl_debug_state *debug,
>     GLint nextEmpty;
>     struct gl_debug_message *emptySlot;
>
> +   if (debug->LogToStderr) {
> +      /* since 'buf' is not null terminated, make a copy and add \0 */
> +      char *buf2 = malloc(len + 1);
> +      if (buf2) {
> +         memcpy(buf2, buf, len);
> +         buf2[len] = 0;
> +         _mesa_log("Mesa debug output: %s\n", buf2);
> +         free(buf2);
> +      }

Using

    _mesa_log("Mesa debug output: %.*s\n", len, buf);

should have the same effect without the additional allocation and copy.

Apart from that, this patch looks like a very good idea and is

Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>

> +   }
> +
>     assert(len < MAX_DEBUG_MESSAGE_LENGTH);
>
>     if (log->NumMessages == MAX_DEBUG_LOGGED_MESSAGES)
> @@ -845,6 +857,7 @@ log_msg_locked_and_unlock(struct gl_context *ctx,
>     }
>
>     if (ctx->Debug->Callback) {
> +      /* Call the user's callback function */
>        GLenum gl_source = debug_source_enums[source];
>        GLenum gl_type = debug_type_enums[type];
>        GLenum gl_severity = debug_severity_enums[severity];
> @@ -860,6 +873,7 @@ log_msg_locked_and_unlock(struct gl_context *ctx,
>        callback(gl_source, gl_type, id, gl_severity, len, buf, data);
>     }
>     else {
> +      /* add debug message to queue */
>        debug_log_message(ctx->Debug, source, type, id, severity, len, buf);
>        _mesa_unlock_debug_state(ctx);
>     }
> @@ -1267,6 +1281,20 @@ void
>  _mesa_init_debug_output(struct gl_context *ctx)
>  {
>     mtx_init(&ctx->DebugMutex, mtx_plain);
> +
> +   if (MESA_DEBUG_FLAGS & DEBUG_CONTEXT) {
> +      /* If the MESA_DEBUG env is set to "context", we'll turn on the
> +       * GL_CONTEXT_FLAG_DEBUG_BIT context flag and log debug output
> +       * messages to stderr (or whatever MESA_LOG_FILE points at).
> +       */
> +      struct gl_debug_state *debug = _mesa_lock_debug_state(ctx);
> +      if (!debug) {
> +         return;
> +      }
> +      debug->DebugOutput = GL_TRUE;
> +      debug->LogToStderr = GL_TRUE;
> +      ctx->Const.ContextFlags |= GL_CONTEXT_FLAG_DEBUG_BIT;
> +   }
>  }
>
>
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 5e98040..66bc07e 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -4679,7 +4679,8 @@ enum _debug
>     DEBUG_SILENT                 = (1 << 0),
>     DEBUG_ALWAYS_FLUSH		= (1 << 1),
>     DEBUG_INCOMPLETE_TEXTURE     = (1 << 2),
> -   DEBUG_INCOMPLETE_FBO         = (1 << 3)
> +   DEBUG_INCOMPLETE_FBO         = (1 << 3),
> +   DEBUG_CONTEXT                = (1 << 4)
>  };
>
>  #ifdef __cplusplus
> diff --git a/src/mesa/state_tracker/st_manager.c b/src/mesa/state_tracker/st_manager.c
> index 0f71e63..c3d8286 100644
> --- a/src/mesa/state_tracker/st_manager.c
> +++ b/src/mesa/state_tracker/st_manager.c
> @@ -680,7 +680,9 @@ st_api_create_context(struct st_api *stapi, struct st_manager *smapi,
>        }
>
>        st->ctx->Const.ContextFlags |= GL_CONTEXT_FLAG_DEBUG_BIT;
> +   }
>
> +   if (st->ctx->Const.ContextFlags & GL_CONTEXT_FLAG_DEBUG_BIT) {
>        st_update_debug_callback(st);
>     }
>
>