sokol_gfx.h: improve warning message on vertex-attr/uniform-block/image-sampler not found in shader (fixes #1184)

sokol_gfx.h

@@ -3685,8 +3685,9 @@ typedef struct sg_frame_stats {
     _SG_LOGITEM_XMACRO(GL_ARRAY_TEXTURES_NOT_SUPPORTED, "array textures not supported (gl)") \
     _SG_LOGITEM_XMACRO(GL_SHADER_COMPILATION_FAILED, "shader compilation failed (gl)") \
     _SG_LOGITEM_XMACRO(GL_SHADER_LINKING_FAILED, "shader linking failed (gl)") \
-    _SG_LOGITEM_XMACRO(GL_VERTEX_ATTRIBUTE_NOT_FOUND_IN_SHADER, "vertex attribute not found in shader (gl)") \
-    _SG_LOGITEM_XMACRO(GL_IMAGE_SAMPLER_NAME_NOT_FOUND_IN_SHADER, "image-sampler name not found in shader (gl)") \
+    _SG_LOGITEM_XMACRO(GL_VERTEX_ATTRIBUTE_NOT_FOUND_IN_SHADER, "vertex attribute not found in shader; NOTE: may be caused by GL driver's GLSL compiler removing unused globals") \
+    _SG_LOGITEM_XMACRO(GL_UNIFORMBLOCK_NAME_NOT_FOUND_IN_SHADER, "uniform block name not found in shader; NOTE: may be caused by GL driver's GLSL compiler removing unused globals") \
+    _SG_LOGITEM_XMACRO(GL_IMAGE_SAMPLER_NAME_NOT_FOUND_IN_SHADER, "image-sampler name not found in shader; NOTE: may be caused by GL driver's GLSL compiler removing unused globals") \
     _SG_LOGITEM_XMACRO(GL_FRAMEBUFFER_STATUS_UNDEFINED, "framebuffer completeness check failed with GL_FRAMEBUFFER_UNDEFINED (gl)") \
     _SG_LOGITEM_XMACRO(GL_FRAMEBUFFER_STATUS_INCOMPLETE_ATTACHMENT, "framebuffer completeness check failed with GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT (gl)") \
     _SG_LOGITEM_XMACRO(GL_FRAMEBUFFER_STATUS_INCOMPLETE_MISSING_ATTACHMENT, "framebuffer completeness check failed with GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT (gl)") \
@@ -8768,6 +8769,10 @@ _SOKOL_PRIVATE sg_resource_state _sg_gl_create_shader(_sg_shader_t* shd, const s
             u->offset = (uint16_t) cur_uniform_offset;
             SOKOL_ASSERT(u_desc->glsl_name);
             u->gl_loc = glGetUniformLocation(gl_prog, u_desc->glsl_name);
+            if (u->gl_loc == -1) {
+                _SG_WARN(GL_UNIFORMBLOCK_NAME_NOT_FOUND_IN_SHADER);
+                _SG_LOGMSG(GL_UNIFORMBLOCK_NAME_NOT_FOUND_IN_SHADER, u_desc->glsl_name);
+            }
             cur_uniform_offset += u_size;
             ub->num_uniforms++;
         }
@@ -8806,7 +8811,7 @@ _SOKOL_PRIVATE sg_resource_state _sg_gl_create_shader(_sg_shader_t* shd, const s
             shd->gl.tex_slot[img_smp_index] = (int8_t)gl_tex_slot++;
         } else {
             shd->gl.tex_slot[img_smp_index] = -1;
-            _SG_ERROR(GL_IMAGE_SAMPLER_NAME_NOT_FOUND_IN_SHADER);
+            _SG_WARN(GL_IMAGE_SAMPLER_NAME_NOT_FOUND_IN_SHADER);
             _SG_LOGMSG(GL_IMAGE_SAMPLER_NAME_NOT_FOUND_IN_SHADER, img_smp_desc->glsl_name);
         }
     }