[NaCl SDK] nacl_io: handle null irt function pointers

native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc

Index: native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
index a264eebd71796437b8cf1800086d0d5e8e1ba609..308a0929ba48e93a4a40e436112b47eedf4a2922 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
@@ -524,14 +524,12 @@ static void assign_real_pointers() {
   }
 }
 
-#define CHECK_REAL(func) \
-  if (!REAL(func))       \
-    assign_real_pointers();
-
-#define CHECK_REAL_NOSYS(func)  \
-  CHECK_REAL(func)              \
-  if (!REAL(func))              \
-    return ENOSYS;
+#define CHECK_REAL(func)    \
+  if (!REAL(func)) {        \
+    assign_real_pointers(); \
+    if (!REAL(func))        \
+      return ENOSYS;        \
+  }
 
 // "real" functions, i.e. the unwrapped original functions.
 
@@ -541,7 +539,8 @@ int _real_close(int fd) {
 }
 
 void _real_exit(int status) {
-  CHECK_REAL(exit);
+  if (!REAL(exit))
+    assign_real_pointers();
   REAL(exit)(status);
 }
 
@@ -639,7 +638,7 @@ int _real_write(int fd, const void* buf, size_t count, size_t* nwrote) {
 }
 
 int _real_getcwd(char* pathname, size_t len) {
-  CHECK_REAL_NOSYS(getcwd);
+  CHECK_REAL(getcwd);
   return REAL(getcwd)(pathname, len);
 }