GPU: Allow printing full shader source on compilation error

Add a define (DEBUG_LOG_SHADER_SRC_ON_ERROR ) in gpu_shader_private.h
to print the full source code of shaders that fail to compile.

Pull Request: https://projects.blender.org/blender/blender/pulls/116470

source/blender/gpu/intern/gpu_shader_log.cc

@@ -245,19 +245,21 @@ void Shader::print_log(Span<const char *> sources,
     log_line = line_end + 1;
     previous_location = log_item.cursor;
   }
-  // printf("%s", sources_combined);
-  MEM_freeN(sources_combined);
 
   CLG_Severity severity = error ? CLG_SEVERITY_ERROR : CLG_SEVERITY_WARN;
 
   if (((LOG.type->flag & CLG_FLAG_USE) && (LOG.type->level >= 0)) ||
       (severity >= CLG_SEVERITY_WARN))
   {
+    if (DEBUG_LOG_SHADER_SRC_ON_ERROR && error) {
+      CLG_log_str(LOG.type, severity, this->name, stage, sources_combined);
+    }
     const char *_str = BLI_dynstr_get_cstring(dynstr);
     CLG_log_str(LOG.type, severity, this->name, stage, _str);
     MEM_freeN((void *)_str);
   }
 
+  MEM_freeN(sources_combined);
   BLI_dynstr_free(dynstr);
 }
 

source/blender/gpu/intern/gpu_shader_private.hh

@@ -25,6 +25,9 @@ namespace gpu {
 
 class GPULogParser;
 
+/* Set to 1 to log the full source of shaders that fail to compile. */
+#define DEBUG_LOG_SHADER_SRC_ON_ERROR 0
+
 /**
  * Compilation is done on a list of GLSL sources. This list contains placeholders that should be
  * provided by the backend shader. These defines contains the locations where the backend can patch

source/blender/gpu/opengl/gl_shader.cc

@@ -1173,6 +1173,30 @@ GLuint GLShader::create_shader_stage(GLenum gl_stage,
   sources[SOURCES_INDEX_VERSION] = glsl_patch_get(gl_stage);
   sources[SOURCES_INDEX_SPECIALIZATION_CONSTANTS] = constants_source.c_str();
 
+  if (DEBUG_LOG_SHADER_SRC_ON_ERROR) {
+    /* Store the generated source for printing in case the link fails. */
+    StringRefNull source_type;
+    switch (gl_stage) {
+      case GL_VERTEX_SHADER:
+        source_type = "VertShader";
+        break;
+      case GL_GEOMETRY_SHADER:
+        source_type = "GeomShader";
+        break;
+      case GL_FRAGMENT_SHADER:
+        source_type = "FragShader";
+        break;
+      case GL_COMPUTE_SHADER:
+        source_type = "ComputeShader";
+        break;
+    }
+
+    debug_source += "\n\n----------" + source_type + "----------\n\n";
+    for (const char *source : sources) {
+      debug_source.append(source);
+    }
+  }
+
   glShaderSource(shader, sources.size(), sources.data(), nullptr);
   glCompileShader(shader);
 
@@ -1510,7 +1534,7 @@ bool GLShader::program_link()
   if (!status) {
     char log[5000];
     glGetProgramInfoLog(program_id, sizeof(log), nullptr, log);
-    Span<const char *> sources;
+    Span<const char *> sources = {debug_source.c_str()};
     GLLogParser parser;
     print_log(sources, log, "Linking", true, &parser);
   }

source/blender/gpu/opengl/gl_shader.hh

@@ -139,6 +139,8 @@ class GLShader : public Shader {
 
   eGPUShaderTFBType transform_feedback_type_ = GPU_SHADER_TFB_NONE;
 
+  std::string debug_source;
+
  public:
   GLShader(const char *name);
   ~GLShader();