s/_alloca/alloca/g; Windows doesn't need the former, at least not unless

__STDC__ is defined (or something like that ...).

Modules/posixmodule.c

@@ -3606,7 +3606,7 @@ _PyPopenCreateProcess(char *cmdstring,
 	if (i = GetEnvironmentVariable("COMSPEC",NULL,0)) {
 		char *comshell;
 
-		s1 = (char *)_alloca(i);
+		s1 = (char *)alloca(i);
 		if (!(x = GetEnvironmentVariable("COMSPEC", s1, i)))
 			return x;
 
@@ -3622,7 +3622,7 @@ _PyPopenCreateProcess(char *cmdstring,
 		    _stricmp(comshell, "command.com") != 0) {
 			/* NT/2000 and not using command.com. */
 			x = i + strlen(s3) + strlen(cmdstring) + 1;
-			s2 = (char *)_alloca(x);
+			s2 = (char *)alloca(x);
 			ZeroMemory(s2, x);
 			PyOS_snprintf(s2, x, "%s%s%s", s1, s3, cmdstring);
 		}
@@ -3675,7 +3675,7 @@ _PyPopenCreateProcess(char *cmdstring,
 				strlen(modulepath) +
 				strlen(szConsoleSpawn) + 1;
 
-			s2 = (char *)_alloca(x);
+			s2 = (char *)alloca(x);
 			ZeroMemory(s2, x);
 			/* To maintain correct argument passing semantics,
 			   we pass the command-line as it stands, and allow

Python/pythonrun.c

@@ -1450,9 +1450,9 @@ int
 PyOS_CheckStack(void)
 {
 	__try {
-		/* _alloca throws a stack overflow exception if there's
+		/* alloca throws a stack overflow exception if there's
 		   not enough space left on the stack */
-		_alloca(PYOS_STACK_MARGIN * sizeof(void*));
+		alloca(PYOS_STACK_MARGIN * sizeof(void*));
 		return 0;
 	} __except (EXCEPTION_EXECUTE_HANDLER) {
 		/* just ignore all errors */