OpenGL: only load extension procs if extension supported.

Only load extension entry points if the extension is supported.

From the eglGetProcAddress manpage:

"A non-NULL return value does not guarantee that an extension function
is actually supported at runtime. The client must also make a
corresponding query, such as glGetString(GL_EXTENSIONS) for OpenGL and
OpenGL ES extensions [...] to determine if a function is supported by
EGL or a specific client API context."

This required moving extension initialization from OpenGLFunctions
into OpenGLFunctionsBase.

Change-Id: Ib4e8360ba455818701990b4476689b651d097ca8
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/121760
Commit-Queue: Stephen White <senorblanco@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

generator/templates/opengl/OpenGLFunctionsBase.cpp

@@ -36,11 +36,15 @@ MaybeError OpenGLFunctionsBase::LoadOpenGLESProcs(GetProcAddress getProc, int ma
 
     {% endfor %}
 
+    InitializeSupportedGLExtensions();
+
     {% for block in extension_gles_blocks %}
         // {{block.extension}}
+        if (IsGLExtensionSupported("{{block.extension}}")) {
             {% for proc in block.procs %}
                 DAWN_TRY(LoadProc(getProc, &{{proc.ProcName()}}, "{{proc.glProcName()}}"));
         {% endfor %}
+        }
     {% endfor %}
 
     return {};
@@ -57,14 +61,33 @@ MaybeError OpenGLFunctionsBase::LoadDesktopGLProcs(GetProcAddress getProc, int m
 
     {% endfor %}
 
+    InitializeSupportedGLExtensions();
+
     {% for block in extension_desktop_gl_blocks %}
         // {{block.extension}}
+        if (IsGLExtensionSupported("{{block.extension}}")) {
             {% for proc in block.procs %}
                 DAWN_TRY(LoadProc(getProc, &{{proc.ProcName()}}, "{{proc.glProcName()}}"));
             {% endfor %}
+        }
     {% endfor %}
 
     return {};
 }
 
+void OpenGLFunctionsBase::InitializeSupportedGLExtensions() {
+    int32_t numExtensions;
+    GetIntegerv(GL_NUM_EXTENSIONS, &numExtensions);
+
+    for (int32_t i = 0; i < numExtensions; ++i) {
+        const char* extensionName = reinterpret_cast<const char*>(GetStringi(GL_EXTENSIONS, i));
+        mSupportedGLExtensionsSet.insert(extensionName);
+    }
+}
+
+bool OpenGLFunctionsBase::IsGLExtensionSupported(const char* extension) const {
+    ASSERT(extension != nullptr);
+    return mSupportedGLExtensionsSet.count(extension) != 0;
+}
+
 }  // namespace dawn::native::opengl

generator/templates/opengl/OpenGLFunctionsBase.h

@@ -15,6 +15,8 @@
 #ifndef DAWNNATIVE_OPENGL_OPENGLFUNCTIONSBASE_H_
 #define DAWNNATIVE_OPENGL_OPENGLFUNCTIONSBASE_H_
 
+#include <unordered_set>
+
 #include "dawn/native/Error.h"
 #include "dawn/native/opengl/opengl_platform.h"
 
@@ -30,6 +32,7 @@ namespace dawn::native::opengl {
             {% endfor %}
 
         {% endfor%}
+        bool IsGLExtensionSupported(const char* extension) const;
 
       protected:
         MaybeError LoadDesktopGLProcs(GetProcAddress getProc, int majorVersion, int minorVersion);
@@ -38,6 +41,9 @@ namespace dawn::native::opengl {
       private:
         template<typename T>
         MaybeError LoadProc(GetProcAddress getProc, T* memberProc, const char* name);
+        void InitializeSupportedGLExtensions();
+
+        std::unordered_set<std::string> mSupportedGLExtensionsSet;
     };
 
 }  // namespace dawn::native::opengl

src/dawn/native/opengl/OpenGLFunctions.cpp

@@ -26,26 +26,9 @@ MaybeError OpenGLFunctions::Initialize(GetProcAddress getProc) {
         DAWN_TRY(LoadDesktopGLProcs(getProc, mVersion.GetMajor(), mVersion.GetMinor()));
     }
 
-    InitializeSupportedGLExtensions();
-
     return {};
 }
 
-void OpenGLFunctions::InitializeSupportedGLExtensions() {
-    int32_t numExtensions;
-    GetIntegerv(GL_NUM_EXTENSIONS, &numExtensions);
-
-    for (int32_t i = 0; i < numExtensions; ++i) {
-        const char* extensionName = reinterpret_cast<const char*>(GetStringi(GL_EXTENSIONS, i));
-        mSupportedGLExtensionsSet.insert(extensionName);
-    }
-}
-
-bool OpenGLFunctions::IsGLExtensionSupported(const char* extension) const {
-    ASSERT(extension != nullptr);
-    return mSupportedGLExtensionsSet.count(extension) != 0;
-}
-
 const OpenGLVersion& OpenGLFunctions::GetVersion() const {
     return mVersion;
 }

src/dawn/native/opengl/OpenGLFunctions.h

@@ -16,7 +16,6 @@
 #define SRC_DAWN_NATIVE_OPENGL_OPENGLFUNCTIONS_H_
 
 #include <string>
-#include <unordered_set>
 
 #include "dawn/native/opengl/OpenGLFunctionsBase_autogen.h"
 #include "dawn/native/opengl/OpenGLVersion.h"
@@ -31,14 +30,8 @@ struct OpenGLFunctions : OpenGLFunctionsBase {
     bool IsAtLeastGL(uint32_t majorVersion, uint32_t minorVersion) const;
     bool IsAtLeastGLES(uint32_t majorVersion, uint32_t minorVersion) const;
 
-    bool IsGLExtensionSupported(const char* extension) const;
-
   private:
-    void InitializeSupportedGLExtensions();
-
     OpenGLVersion mVersion;
-
-    std::unordered_set<std::string> mSupportedGLExtensionsSet;
 };
 
 }  // namespace dawn::native::opengl