From a533f857e7d319c6eff2b788bbad3a238468c4b2 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 10 Oct 2013 15:24:09 +0300
Subject: [PATCH] Get function pointers on OS X through weak symbols

---
 scripts/extgen.py | 50 +++++++++++++++++++++++------------------------
 source/gl.h       |  2 ++
 2 files changed, 27 insertions(+), 25 deletions(-)

diff --git a/scripts/extgen.py b/scripts/extgen.py
index 6c0ef8f1..7ab8abc3 100755
--- a/scripts/extgen.py
+++ b/scripts/extgen.py
@@ -252,26 +252,26 @@ out.write("""
 
 namespace Msp {
 namespace GL {
+
 """)
 
 if funcs or enums:
-	out.write("\n#ifndef GL_%s\n"%ext)
-	for f in funcs:
-		out.write("typedef %s (*%s)(%s);\n"%(f.return_type, f.typedef, ", ".join(f.params)))
-	if funcs and enums:
-		out.write("\n")
-	for e in enums:
-		out.write("#define %s 0x%04X\n"%(e.name, e.value))
-	out.write("#endif\n\n")
-
-	# Apple's OpenGL implementation doesn't have a GetProcAddress function; link
-	# directly to the OpenGL library
-	out.write("\n#if !defined(__APPLE__) || !defined(GL_%s)\n"%ext)
+	if funcs:
+		out.write("#if defined(__APPLE__) || !defined(GL_%s)\n"%ext)
+		for f in funcs:
+			out.write("typedef %s (*%s)(%s);\n"%(f.return_type, f.typedef, ", ".join(f.params)))
+		out.write("#endif\n\n")
+
+	if enums:
+		out.write("#ifndef GL_%s\n"%ext)
+		for e in enums:
+			out.write("#define %s 0x%04X\n"%(e.name, e.value))
+		out.write("#endif\n\n")
+
 	for f in funcs:
 		out.write("extern %s %s;\n"%(f.typedef, f.name))
-	out.write("#endif\n")
 
-out.write("\nextern Extension %s;\n"%ext)
+out.write("extern Extension %s;\n"%ext)
 
 out.write("""
 } // namespace GL
@@ -284,15 +284,19 @@ out = file(out_base+".cpp", "w")
 out.write("#include \"%s.h\"\n"%ext.lower())
 
 out.write("""
+#ifdef __APPLE__
+#define GET_PROC_ADDRESS(x) ::x
+#else
+#define GET_PROC_ADDRESS(x) get_proc_address(#x)
+#endif
+
 namespace Msp {
 namespace GL {
+
 """)
 
-if funcs:
-	out.write("\n#if !defined(__APPLE__) || !defined(GL_%s)\n"%ext)
-	for f in funcs:
-		out.write("%s %s = 0;\n"%(f.typedef, f.name))
-	out.write("\n#endif\n")
+for f in funcs:
+	out.write("%s %s = 0;\n"%(f.typedef, f.name))
 
 out.write("\nExtension::SupportLevel init_%s()\n{\n"%ext.lower())
 out.write("#ifdef GL_%s\n"%ext)
@@ -302,22 +306,18 @@ if ver:
 		out.write(" || is_supported(\"GL_%s\")"%backport_ext)
 	out.write(")\n\t{\n")
 	if funcs:
-		out.write("#ifndef __APPLE__\n")
 		for f in funcs:
-			out.write("\t\t%s = reinterpret_cast<%s>(get_proc_address(\"%s\"));\n"%(f.name, f.typedef, f.name))
-		out.write("#endif\n")
+			out.write("\t\t%s = reinterpret_cast<%s>(GET_PROC_ADDRESS(%s));\n"%(f.name, f.typedef, f.name))
 	out.write("\t\treturn Extension::CORE;\n")
 	out.write("\t}\n")
 if ext!=backport_ext:
 	out.write("\tif(is_supported(\"GL_%s\"))\n\t{\n"%(ext))
 	if funcs:
-		out.write("#ifndef __APPLE__\n")
 		for f in funcs:
 			n = f.name
 			if f.source:
 				n = f.source.name
-			out.write("\t\t%s = reinterpret_cast<%s>(get_proc_address(\"%s\"));\n"%(f.name, f.typedef, n))
-		out.write("#endif\n")
+			out.write("\t\t%s = reinterpret_cast<%s>(GET_PROC_ADDRESS(%s));\n"%(f.name, f.typedef, n))
 	out.write("\t\treturn Extension::EXTENSION;\n")
 	out.write("\t}\n")
 out.write("#endif\n")
diff --git a/source/gl.h b/source/gl.h
index 05844ba5..255242bf 100644
--- a/source/gl.h
+++ b/source/gl.h
@@ -5,8 +5,10 @@
 #include <windows.h>
 #endif
 #ifdef __APPLE__
+#define extern extern __attribute__((weak_import))
 #include <OpenGL/gl.h>
 #include <OpenGL/glext.h>
+#undef extern
 #else
 #include <GL/gl.h>
 #include <GL/glext.h>
-- 
2.43.0