Fix linking of non-existent XFB varyings with gl_ prefix

src/libANGLE/VaryingPacking.cpp

@@ -259,39 +259,35 @@ bool VaryingPacking::packUserVaryings(gl::InfoLog &infoLog,
         }
     }
 
+    // Make sure transform feedback varyings aren't optimized out.
     for (const std::string &transformFeedbackVaryingName : transformFeedbackVaryings)
     {
-        if (transformFeedbackVaryingName.compare(0, 3, "gl_") == 0)
-        {
-            // do not pack builtin XFB varyings
-            continue;
-        }
+        size_t subscript              = GL_INVALID_INDEX;
+        std::string tfVaryingBaseName = ParseResourceName(transformFeedbackVaryingName, &subscript);
 
-        bool found = false;
-        for (const PackedVarying &packedVarying : packedVaryings)
-        {
-            const auto &varying = *packedVarying.varying;
-            size_t subscript     = GL_INVALID_INDEX;
-            std::string baseName = ParseResourceName(transformFeedbackVaryingName, &subscript);
+        bool found = (uniqueVaryingNames.count(transformFeedbackVaryingName) > 0 ||
+                      uniqueVaryingNames.count(tfVaryingBaseName) > 0);
 
-            // Make sure transform feedback varyings aren't optimized out.
-            if (uniqueVaryingNames.count(transformFeedbackVaryingName) > 0 ||
-                uniqueVaryingNames.count(baseName) > 0)
-            {
-                found = true;
-                break;
-            }
-
-            if (baseName == varying.name)
+        if (!found)
+        {
+            for (const PackedVarying &packedVarying : packedVaryings)
             {
-                if (!packVarying(packedVarying))
+                const auto &varying = *packedVarying.varying;
+                if (tfVaryingBaseName == varying.name)
                 {
-                    infoLog << "Could not pack varying " << varying.name;
-                    return false;
+                    // only pack varyings that are not builtins.
+                    if (transformFeedbackVaryingName.compare(0, 3, "gl_") != 0)
+                    {
+                        if (!packVarying(packedVarying))
+                        {
+                            infoLog << "Could not pack varying " << varying.name;
+                            return false;
+                        }
+                        uniqueVaryingNames.insert(packedVarying.nameWithArrayIndex());
+                    }
+                    found = true;
+                    break;
                 }
-                uniqueVaryingNames.insert(packedVarying.nameWithArrayIndex());
-                found = true;
-                break;
             }
         }
 

src/tests/gl_tests/TransformFeedbackTest.cpp

@@ -1213,21 +1213,18 @@ TEST_P(TransformFeedbackTest, NonExistentTransformFeedbackVarying)
     const std::string &vertexShaderSource =
         "#version 300 es\n"
         "in vec4 a_position;\n"
-        "out vec4 v_position;\n"
         "void main()\n"
         "{\n"
-        "    v_position = a_position;\n"
         "    gl_Position = a_position;\n"
         "}\n";
 
     const std::string &fragmentShaderSource =
         "#version 300 es\n"
         "precision mediump float;\n"
-        "in vec4 v_position;\n"
         "out vec4 fragColor;\n"
         "void main()\n"
         "{\n"
-        "    fragColor = v_position;\n"
+        "    fragColor = vec4(0);\n"
         "}\n";
 
     std::vector<std::string> tfVaryings;
@@ -1238,6 +1235,35 @@ TEST_P(TransformFeedbackTest, NonExistentTransformFeedbackVarying)
     ASSERT_EQ(0u, mProgram);
 }
 
+// Test that nonexistent transform feedback varyings don't assert when linking. In this test the
+// nonexistent varying is prefixed with "gl_".
+TEST_P(TransformFeedbackTest, NonExistentTransformFeedbackVaryingWithGLPrefix)
+{
+    const std::string &vertexShaderSource =
+        "#version 300 es\n"
+        "in vec4 a_position;\n"
+        "void main()\n"
+        "{\n"
+        "    gl_Position = a_position;\n"
+        "}\n";
+
+    const std::string &fragmentShaderSource =
+        "#version 300 es\n"
+        "precision mediump float;\n"
+        "out vec4 fragColor;\n"
+        "void main()\n"
+        "{\n"
+        "    fragColor = vec4(0);\n"
+        "}\n";
+
+    std::vector<std::string> tfVaryings;
+    tfVaryings.push_back("gl_Bogus");
+
+    mProgram = CompileProgramWithTransformFeedback(vertexShaderSource, fragmentShaderSource,
+                                                   tfVaryings, GL_INTERLEAVED_ATTRIBS);
+    ASSERT_EQ(0u, mProgram);
+}
+
 // Test transform feedback names can be reserved names in GLSL, as long as they're not reserved in
 // GLSL ES.
 TEST_P(TransformFeedbackTest, VaryingReservedOpenGLName)