--- setup.py
+++ setup.py
@@ -655,7 +655,10 @@
             add_dir_to_list(self.compiler.include_dirs,
                             sysconfig.get_config_var("INCLUDEDIR"))
 
-        system_lib_dirs = ['/lib64', '/usr/lib64', '/lib', '/usr/lib']
+        if MACOS:
+            system_lib_dirs = ['/usr/lib', macosx_sdk_root()+'/usr/lib']
+        else:
+            system_lib_dirs = ['/lib64', '/usr/lib64', '/lib', '/usr/lib']
         system_include_dirs = ['/usr/include']
         # lib_dirs and inc_dirs are used to search for files;
         # if a file is found in one of those directories, it can
--- Modules/_posixsubprocess.c
+++ Modules/_posixsubprocess.c
@@ -30,6 +30,8 @@
 # define SYS_getdents64  __NR_getdents64
 #endif
 
+#include <limits.h>
+
 #if defined(__sun) && defined(__SVR4)
 /* readdir64 is used to work around Solaris 9 bug 6395699. */
 # define readdir readdir64
@@ -201,7 +203,7 @@
 #endif
 #ifdef _SC_OPEN_MAX
     local_max_fd = sysconf(_SC_OPEN_MAX);
-    if (local_max_fd == -1)
+    if (local_max_fd == -1 || local_max_fd == LONG_MAX)
 #endif
         local_max_fd = 256;  /* Matches legacy Lib/subprocess.py behavior. */
     return local_max_fd;