[core] check GL errors in loop

As recommended in https://www.opengl.org/wiki/GLAPI/glGetError

char* -> std::string

include/mbgl/gl/gl.hpp

@@ -59,9 +59,8 @@ namespace gl {
     void mbx_trapExtension(const char *name, GLuint array);
 #endif
 
-struct Error : ::std::runtime_error {
-    Error(GLenum err, const std::string &msg) : ::std::runtime_error(msg), code(err) {};
-    const GLenum code;
+struct Error : std::runtime_error {
+    using std::runtime_error::runtime_error;
 };
 
 void checkError(const char *cmd, const char *file, int line);

src/mbgl/gl/gl.cpp

@@ -61,31 +61,67 @@ void InitializeExtensions(glProc (*getProcAddress)(const char *)) {
     });
 }
 
-void checkError(const char *cmd, const char *file, int line) {
-    const GLenum err = glGetError();
-    if (err != GL_NO_ERROR) {
-        const char *error = nullptr;
-        switch (err) {
-            case GL_INVALID_ENUM: error = "INVALID_ENUM"; break;
-            case GL_INVALID_VALUE: error = "INVALID_VALUE"; break;
-            case GL_INVALID_OPERATION: error = "INVALID_OPERATION"; break;
-#ifdef GL_STACK_OVERFLOW
-            case GL_STACK_OVERFLOW:  error = "STACK_OVERFLOW";  break;
-#endif
-#ifdef GL_STACK_UNDERFLOW
-            case GL_STACK_UNDERFLOW:  error = "STACK_UNDERFLOW";  break;
-#endif
-            case GL_OUT_OF_MEMORY: error = "OUT_OF_MEMORY"; break;
-            case GL_INVALID_FRAMEBUFFER_OPERATION:  error = "INVALID_FRAMEBUFFER_OPERATION";  break;
-#ifdef GL_CONTEXT_LOST
-            case GL_CONTEXT_LOST:  error = "CONTEXT_LOST";  break;
-#endif
-            default: error = "(unknown)"; break;
-        }
+namespace {
 
-        throw ::mbgl::gl::Error(err, std::string(cmd) + ": Error GL_" + error + " - " + file + ":" + util::toString(line));
+constexpr const char* stringFromError(GLenum err) {
+    switch (err) {
+    case GL_INVALID_ENUM:
+        return "GL_INVALID_ENUM";
+
+    case GL_INVALID_VALUE:
+        return "GL_INVALID_VALUE";
+
+    case GL_INVALID_OPERATION:
+        return "GL_INVALID_OPERATION";
+
+    case GL_INVALID_FRAMEBUFFER_OPERATION:
+        return "GL_INVALID_FRAMEBUFFER_OPERATION";
+
+    case GL_OUT_OF_MEMORY:
+        return "GL_OUT_OF_MEMORY";
+
+#ifdef GL_TABLE_TOO_LARGE
+    case GL_TABLE_TOO_LARGE:
+        return "GL_TABLE_TOO_LARGE";
+#endif
+
+#ifdef GL_STACK_OVERFLOW
+    case GL_STACK_OVERFLOW:
+        return "GL_STACK_OVERFLOW";
+#endif
+
+#ifdef GL_STACK_UNDERFLOW
+    case GL_STACK_UNDERFLOW:
+        return "GL_STACK_UNDERFLOW";
+#endif
+
+#ifdef GL_CONTEXT_LOST
+    case GL_CONTEXT_LOST:
+        return "GL_CONTEXT_LOST";
+#endif
+
+    default:
+        return "GL_UNKNOWN";
     }
 }
+
+} // namespace
+
+void checkError(const char* cmd, const char* file, int line) {
+    GLenum err = GL_NO_ERROR;
+    if ((err = glGetError()) != GL_NO_ERROR) {
+        std::string message = std::string(cmd) + ": Error " + stringFromError(err);
+
+        // Check for further errors
+        while ((err = glGetError()) != GL_NO_ERROR) {
+            message += ", ";
+            message += stringFromError(err);
+        }
+
+        throw Error(message + " at " + file + ":" + util::toString(line));
+    }
+}
+
 } // namespace gl
 } // namespace mbgl