GLShader: Fix buffer overflow caused by workaround uniform

In order to use a workaround builtin uniform, we need to count it
just like other uniforms and give it some space in the name buffer.

This also fixes extensions being added after the uniform declaration.
All `#extension` directives are now part of the gl backend.

6 files changed, 38 insertions, 18 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_shaders.c b/source/blender/draw/engines/eevee/eevee_shaders.c
index e56097df6b7..c4108969c99 100644
--- a/source/blender/draw/engines/eevee/eevee_shaders.c
+++ b/source/blender/draw/engines/eevee/eevee_shaders.c
@@ -887,10 +887,7 @@ struct GPUShader *EEVEE_shaders_volumes_integration_sh_get()
         datatoc_volumetric_geom_glsl,
         datatoc_volumetric_integration_frag_glsl,
         e_data.lib,
-        USE_VOLUME_OPTI ? "#extension GL_ARB_shader_image_load_store: enable\n"
-                          "#extension GL_ARB_shading_language_420pack: enable\n"
-                          "#define USE_VOLUME_OPTI\n" SHADER_DEFINES :
-                          SHADER_DEFINES);
+        USE_VOLUME_OPTI ? "#define USE_VOLUME_OPTI\n" SHADER_DEFINES : SHADER_DEFINES);
   }
   return e_data.volumetric_integration_sh;
 }
diff --git a/source/blender/draw/engines/overlay/overlay_shader.c b/source/blender/draw/engines/overlay/overlay_shader.c
index 9899dce5df6..4c09349c35d 100644
--- a/source/blender/draw/engines/overlay/overlay_shader.c
+++ b/source/blender/draw/engines/overlay/overlay_shader.c
@@ -385,7 +385,7 @@ GPUShader *OVERLAY_shader_armature_sphere(bool use_outline)
   const DRWContextState *draw_ctx = DRW_context_state_get();
   const GPUShaderConfigData *sh_cfg = &GPU_shader_cfg_data[draw_ctx->sh_cfg];
   OVERLAY_Shaders *sh_data = &e_data.sh_data[draw_ctx->sh_cfg];
-  const char extensions[] = "#extension GL_ARB_conservative_depth : enable\n";
+  const char extensions[] = "";
   if (use_outline && !sh_data->armature_sphere_outline) {
     sh_data->armature_sphere_outline = GPU_shader_create_from_arrays({
         .vert = (const char *[]){sh_cfg->lib,
diff --git a/source/blender/draw/engines/workbench/shaders/workbench_shadow_caps_geom.glsl b/source/blender/draw/engines/workbench/shaders/workbench_shadow_caps_geom.glsl
index 09bafb8ff11..1f172de1e12 100644
--- a/source/blender/draw/engines/workbench/shaders/workbench_shadow_caps_geom.glsl
+++ b/source/blender/draw/engines/workbench/shaders/workbench_shadow_caps_geom.glsl
@@ -1,5 +1,3 @@
-#extension GL_ARB_gpu_shader5 : enable
-
 #ifdef GL_ARB_gpu_shader5
 #  define USE_INVOC_EXT
 #endif
diff --git a/source/blender/draw/engines/workbench/shaders/workbench_shadow_geom.glsl b/source/blender/draw/engines/workbench/shaders/workbench_shadow_geom.glsl
index 2c9190bfcf4..b49ade13034 100644
--- a/source/blender/draw/engines/workbench/shaders/workbench_shadow_geom.glsl
+++ b/source/blender/draw/engines/workbench/shaders/workbench_shadow_geom.glsl
@@ -1,5 +1,3 @@
-#extension GL_ARB_gpu_shader5 : enable
-
 #ifdef GL_ARB_gpu_shader5
 #  define USE_INVOC_EXT
 #endif
diff --git a/source/blender/gpu/opengl/gl_shader.cc b/source/blender/gpu/opengl/gl_shader.cc
index 532065ed08f..ac9aec5af04 100644
--- a/source/blender/gpu/opengl/gl_shader.cc
+++ b/source/blender/gpu/opengl/gl_shader.cc
@@ -587,6 +587,18 @@ static char *glsl_patch_default_get()
     STR_CONCAT(patch, slen, "#extension GL_ARB_texture_cube_map_array : enable\n");
     STR_CONCAT(patch, slen, "#define GPU_ARB_texture_cube_map_array\n");
   }
+  if (GLEW_ARB_conservative_depth) {
+    STR_CONCAT(patch, slen, "#extension GL_ARB_conservative_depth : enable\n");
+  }
+  if (GPU_shader_image_load_store_support()) {
+    STR_CONCAT(patch, slen, "#extension GL_ARB_shader_image_load_store: enable\n");
+    STR_CONCAT(patch, slen, "#extension GL_ARB_shading_language_420pack: enable\n");
+  }
+
+  if (!GLContext::shader_draw_parameters_support) {
+    /* Fallback: Emulate base instance using a uniform. */
+    STR_CONCAT(patch, slen, "uniform int gpu_BaseInstance;\n");
+  }
 
   /* Fallbacks. */
   if (!GLContext::shader_draw_parameters_support) {
diff --git a/source/blender/gpu/opengl/gl_shader_interface.cc b/source/blender/gpu/opengl/gl_shader_interface.cc
index 4414ba0464b..299ea150408 100644
--- a/source/blender/gpu/opengl/gl_shader_interface.cc
+++ b/source/blender/gpu/opengl/gl_shader_interface.cc
@@ -355,13 +355,28 @@ GLShaderInterface::GLShaderInterface(GLuint program, const shader::ShaderCreateI
     }
   }
 
+  size_t workaround_names_size = 0;
+  Vector<StringRefNull> workaround_uniform_names;
+  auto check_enabled_uniform = [&](const char *uniform_name) {
+    if (glGetUniformLocation(program, uniform_name) != -1) {
+      workaround_uniform_names.append(uniform_name);
+      workaround_names_size += StringRefNull(uniform_name).size() + 1;
+      uniform_len_++;
+    }
+  };
+
+  if (!GLContext::shader_draw_parameters_support) {
+    check_enabled_uniform("gpu_BaseInstance");
+  }
+
   BLI_assert_msg(ubo_len_ <= 16, "enabled_ubo_mask_ is uint16_t");
 
   int input_tot_len = attr_len_ + ubo_len_ + uniform_len_ + ssbo_len_;
   inputs_ = (ShaderInput *)MEM_callocN(sizeof(ShaderInput) * input_tot_len, __func__);
   ShaderInput *input = inputs_;
 
-  name_buffer_ = (char *)MEM_mallocN(info.interface_names_size_, "name_buffer");
+  name_buffer_ = (char *)MEM_mallocN(info.interface_names_size_ + workaround_names_size,
+                                     "name_buffer");
   uint32_t name_buffer_offset = 0;
 
   /* Necessary to make #glUniform works. TODO(fclem) Remove. */
@@ -430,6 +445,14 @@ GLShaderInterface::GLShaderInterface(GLuint program, const shader::ShaderCreateI
     input++;
   }
 
+  /* Compatibility uniforms. */
+  for (auto &name : workaround_uniform_names) {
+    copy_input_name(input, name, name_buffer_, name_buffer_offset);
+    input->location = glGetUniformLocation(program, name_buffer_ + input->name_offset);
+    input->binding = -1;
+    input++;
+  }
+
   /* SSBOs */
   for (const ShaderCreateInfo::Resource &res : all_resources) {
     if (res.bind_type == ShaderCreateInfo::Resource::BindType::STORAGE_BUFFER) {
@@ -440,14 +463,6 @@ GLShaderInterface::GLShaderInterface(GLuint program, const shader::ShaderCreateI
     }
   }
 
-  /* Compatibility uniforms. */
-  if (!GLContext::shader_draw_parameters_support) {
-    input->location = glGetUniformLocation(program, "gpu_BaseInstance");
-    copy_input_name(input, "gpu_BaseInstance", name_buffer_, name_buffer_offset);
-    input->binding = -1;
-    input++;
-  }
-
   /* Builtin Uniforms */
   for (int32_t u_int = 0; u_int < GPU_NUM_UNIFORMS; u_int++) {
     GPUUniformBuiltin u = static_cast<GPUUniformBuiltin>(u_int);