bpo-37415: Fix stdatomic.h header check for ICC compiler (GH-16717)

Fix stdatomic.h header check for ICC compiler: the ICC implementation
lacks atomic_uintptr_t type which is needed by Python.

Test:

* atomic_int and atomic_uintptr_t types
* atomic_load_explicit() and atomic_store_explicit()
* memory_order_relaxed and memory_order_seq_cst constants

But don't test ATOMIC_VAR_INIT(): it's not used in Python.
(cherry picked from commit 028f734)

Co-authored-by: Victor Stinner <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/Build/2019-10-11-15-32-58.bpo-37415.D9RXrq.rst

@@ -0,0 +1,2 @@
+Fix stdatomic.h header check for ICC compiler: the ICC implementation lacks
+atomic_uintptr_t type which is needed by Python.

configure

@@ -16849,9 +16849,12 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 
 
     #include <stdatomic.h>
-    atomic_int value = ATOMIC_VAR_INIT(1);
+    atomic_int int_var;
+    atomic_uintptr_t uintptr_var;
     int main() {
-      int loaded_value = atomic_load(&value);
+      atomic_store_explicit(&int_var, 5, memory_order_relaxed);
+      atomic_store_explicit(&uintptr_var, 0, memory_order_relaxed);
+      int loaded_value = atomic_load_explicit(&int_var, memory_order_seq_cst);
       return 0;
     }
 

configure.ac

@@ -5492,9 +5492,12 @@ AC_LINK_IFELSE(
 [
   AC_LANG_SOURCE([[
     #include <stdatomic.h>
-    atomic_int value = ATOMIC_VAR_INIT(1);
+    atomic_int int_var;
+    atomic_uintptr_t uintptr_var;
     int main() {
-      int loaded_value = atomic_load(&value);
+      atomic_store_explicit(&int_var, 5, memory_order_relaxed);
+      atomic_store_explicit(&uintptr_var, 0, memory_order_relaxed);
+      int loaded_value = atomic_load_explicit(&int_var, memory_order_seq_cst);
       return 0;
     }
   ]])
@@ -5504,7 +5507,7 @@ AC_MSG_RESULT($have_stdatomic_h)
 
 if test "$have_stdatomic_h" = yes; then
     AC_DEFINE(HAVE_STD_ATOMIC, 1,
-              [Has stdatomic.h with atomic_int])
+              [Has stdatomic.h with atomic_int and atomic_uintptr_t])
 fi
 
 # Check for GCC >= 4.7 __atomic builtins

pyconfig.h.in

@@ -963,7 +963,7 @@
 /* Define to 1 if you have the <stdlib.h> header file. */
 #undef HAVE_STDLIB_H
 
-/* Has stdatomic.h with atomic_int */
+/* Has stdatomic.h with atomic_int and atomic_uintptr_t */
 #undef HAVE_STD_ATOMIC
 
 /* Define to 1 if you have the `strdup' function. */