Replace GCC's attribute optimize("Os") by the better supported and similar (cold).

Closes #2494.

CHANGES.rst

@@ -57,6 +57,10 @@ Bugs fixed
   exception stack traces.
   Patch by Jeroen Demeyer.  (Github issue #2492)
 
+* The discouraged usage of GCC's attribute ``optimize("Os")`` was replaced by the
+  similar attribute ``cold`` to reduce the code impact of the module init functions.
+  (Github issue #2494)
+
 Other changes
 -------------
 

Cython/Utility/ModuleSetupCode.c

@@ -677,9 +677,8 @@ static CYTHON_INLINE void * PyThread_tss_get(Py_tss_t *key) {
 #ifndef CYTHON_SMALL_CODE
 #if defined(__clang__)
     #define CYTHON_SMALL_CODE
-#elif defined(__GNUC__) && (!(defined(__cplusplus)) || (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 4)))
-    // At least g++ 4.4.7 can generate crashing code with this option. (GH #2235)
-    #define CYTHON_SMALL_CODE __attribute__((optimize("Os")))
+#elif defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
+    #define CYTHON_SMALL_CODE __attribute__((cold))
 #else
     #define CYTHON_SMALL_CODE
 #endif