[Mesa-dev] [PATCH] shaderapi: don't generate not linked error on GetProgramStage in general

[Alejandro Piñeiro]

Both ARB_shader_subroutine and the GL core spec doesn't list any
error when the program is not linked.

We left a error generation for the uniform location, in order to be
consistent with other methods from the spec that generate them.
---

On 23/08/16 10:14, Tapani Pälli wrote:

> IMO it looks like GetProgramStageiv is currently not correct from this
> perspective as it does not follow these rules, it should not require
> linking either as GL_ARB_shader_subroutine spec does not specify such
> for the call.

This patch tries to put some coherence between both specs. Having said
so I found this to be tricky, as GetProgramStageiv also allow tos ask
for uniform locations. The rest of the methods at the subroutine spec
generates an error if asking for locations when the program is not linked.

So I went for the compromise of keep this method not generate errors
when the program is not linked in general, as the spec for the method
points, but still generates the error for uniform location, trying to be
coherent with other methods.

Or in other words: I tried to be as coherent as possible, but failing to
be be 100% coherent and follow the spec 100% at the same time.


 src/mesa/main/shaderapi.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/mesa/main/shaderapi.c b/src/mesa/main/shaderapi.c
index 4f29cd9..6806c02 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -2745,8 +2745,25 @@ _mesa_GetProgramStageiv(GLuint program, GLenum shadertype,
 
    stage = _mesa_shader_enum_to_shader_stage(shadertype);
    sh = shProg->_LinkedShaders[stage];
+
+   /* ARB_shader_subroutine doesn't ask the program to be linked, or list any
+    * INVALID_OPERATION in the case of not be linked.
+    *
+    * And for some pnames, like GL_ACTIVE_SUBROUTINE_UNIFORMS, you can ask the
+    * same info using other specs (ARB_program_interface_query), without the
+    * need of the program to be linked, being the value for that case 0.
+    *
+    * But at the same time, some other methods require the program to be
+    * linked for pname related to locations, so it would be inconsistent to
+    * not do the same here. So we are:
+    *   * Return GL_INVALID_OPERATION if not linked only for locations.
+    *   * Setting a default value of 0, to be returned if not linked.
+    */
    if (!sh) {
-      _mesa_error(ctx, GL_INVALID_OPERATION, "%s", api_name);
+      values[0] = 0;
+      if (pname == GL_ACTIVE_SUBROUTINE_UNIFORM_LOCATIONS) {
+         _mesa_error(ctx, GL_INVALID_OPERATION, "%s", api_name);
+      }
       return;
    }
 
-- 
2.7.4