Manual Leopard SDK Fixes

Leopard's SDK has a couple bugs which were never fixed in an update of Xcode or the OS. While some ports used to work around these bugs in the past, Leopard is past EndOfLife and encountering code that does not work around these issues is common. You should make these changes to the relevant files in both / and /Developer/SDKs/MacOSX10.5.sdk

Missing symbols in /usr/lib/libgcc_s.10.5.dylib

Update /usr/lib/libgcc_s.10.5.dylib from a newer OS (to get the missing stubs for __udivti3 and others):

sudo cp /usr/lib/libgcc_s.10.5.dylib{,.bak}
sudo scp <snow leopard or newer machine>:/usr/lib/libgcc_s.10.5.dylib /usr/lib/libgcc_s.10.5.dylib

You will know that this worked successfully if you can compile this with clang-mp-3.4:

int main() {
   __uint128_t a = 100;
   __uint128_t b = 200;
   __uint128_t c = a / b;

  return 0;
}

Incorrect __MAC_OS_X_VERSION_MAX_ALLOWED

Edit /usr/include/AvailabilityInternal.h, so ports don't try to use API that were added in Snow Leopard:

--- /usr/include/AvailabilityInternal.h.orig    2015-01-11 17:31:10.000000000 -0800
+++ /usr/include/AvailabilityInternal.h 2015-01-05 04:15:01.000000000 -0800
@@ -60,7 +60,7 @@
     #define __MAC_OS_X_VERSION_MIN_REQUIRED __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
     // make sure a default max version is set
     #ifndef __MAC_OS_X_VERSION_MAX_ALLOWED
-        #define __MAC_OS_X_VERSION_MAX_ALLOWED __MAC_10_6
+        #define __MAC_OS_X_VERSION_MAX_ALLOWED 1058
     #endif
 
     // set up internal macros

You may be tempted to use __MAC_10_5 instead of 1058 there to match what is done on Snow Leopard and later SDKs, but that will fail with Leopard's default toolchain because it sets the deployment target to the full OS version (eg 10.5.8), and that needs to be less than or equal to __MAC_OS_X_VERSION_MAX_ALLOWED.