[Sema][Atomics] Treat expected pointer in compare exchange atomics as…

… _Nonnull

This commit teaches clang that is has to emit a warning when NULL is passed
as the 'expected' pointer parameter into an atomic compare exchange call.

rdar://18926650

Differential Revision: https://reviews.llvm.org/D26978

llvm-svn: 287776

clang/lib/Sema/SemaChecking.cpp

@@ -2868,6 +2868,9 @@ ExprResult Sema::SemaAtomicOpsOverloaded(ExprResult TheCallResult,
           Ty = Context.getPointerDiffType();
         else {
           Expr *ValArg = TheCall->getArg(i);
+          // Treat this argument as _Nonnull as we want to show a warning if
+          // NULL is passed into it.
+          CheckNonNullArgument(*this, ValArg, DRE->getLocStart());
           unsigned AS = 0;
           // Keep address space of non-atomic pointer type.
           if (const PointerType *PtrTy =

clang/test/Sema/atomic-ops.c

@@ -174,14 +174,14 @@ void f(_Atomic(int) *i, const _Atomic(int) *ci,
   __atomic_fetch_or(D, 3, memory_order_seq_cst); // expected-error {{must be a pointer to integer}}
   __atomic_fetch_and(s1, 3, memory_order_seq_cst); // expected-error {{must be a pointer to integer}}
 
-  _Bool cmpexch_1 = __c11_atomic_compare_exchange_strong(i, 0, 1, memory_order_seq_cst, memory_order_seq_cst);
-  _Bool cmpexch_2 = __c11_atomic_compare_exchange_strong(p, 0, (int*)1, memory_order_seq_cst, memory_order_seq_cst);
-  _Bool cmpexch_3 = __c11_atomic_compare_exchange_strong(d, (int*)0, 1, memory_order_seq_cst, memory_order_seq_cst); // expected-warning {{incompatible pointer types}}
+  _Bool cmpexch_1 = __c11_atomic_compare_exchange_strong(i, I, 1, memory_order_seq_cst, memory_order_seq_cst);
+  _Bool cmpexch_2 = __c11_atomic_compare_exchange_strong(p, P, (int*)1, memory_order_seq_cst, memory_order_seq_cst);
+  _Bool cmpexch_3 = __c11_atomic_compare_exchange_strong(d, I, 1, memory_order_seq_cst, memory_order_seq_cst); // expected-warning {{incompatible pointer types}}
   (void)__c11_atomic_compare_exchange_strong(i, CI, 1, memory_order_seq_cst, memory_order_seq_cst); // expected-warning {{passing 'const int *' to parameter of type 'int *' discards qualifiers}}
 
-  _Bool cmpexchw_1 = __c11_atomic_compare_exchange_weak(i, 0, 1, memory_order_seq_cst, memory_order_seq_cst);
-  _Bool cmpexchw_2 = __c11_atomic_compare_exchange_weak(p, 0, (int*)1, memory_order_seq_cst, memory_order_seq_cst);
-  _Bool cmpexchw_3 = __c11_atomic_compare_exchange_weak(d, (int*)0, 1, memory_order_seq_cst, memory_order_seq_cst); // expected-warning {{incompatible pointer types}}
+  _Bool cmpexchw_1 = __c11_atomic_compare_exchange_weak(i, I, 1, memory_order_seq_cst, memory_order_seq_cst);
+  _Bool cmpexchw_2 = __c11_atomic_compare_exchange_weak(p, P, (int*)1, memory_order_seq_cst, memory_order_seq_cst);
+  _Bool cmpexchw_3 = __c11_atomic_compare_exchange_weak(d, I, 1, memory_order_seq_cst, memory_order_seq_cst); // expected-warning {{incompatible pointer types}}
   (void)__c11_atomic_compare_exchange_weak(i, CI, 1, memory_order_seq_cst, memory_order_seq_cst); // expected-warning {{passing 'const int *' to parameter of type 'int *' discards qualifiers}}
 
   _Bool cmpexch_4 = __atomic_compare_exchange_n(I, I, 5, 1, memory_order_seq_cst, memory_order_seq_cst);
@@ -503,4 +503,9 @@ void memory_checks(_Atomic(int) *Ap, int *p, int val) {
   (void)__atomic_compare_exchange_n(p, p, val, 0, memory_order_seq_cst, memory_order_relaxed);
 }
 
-
+void nullPointerWarning(_Atomic(int) *Ap, int *p, int val) {
+  // The 'expected' pointer shouldn't be NULL.
+  (void)__c11_atomic_compare_exchange_strong(Ap, NULL, val, memory_order_relaxed, memory_order_relaxed); // expected-warning {{null passed to a callee that requires a non-null argument}}
+  (void)atomic_compare_exchange_weak(Ap, ((void*)0), val); // expected-warning {{null passed to a callee that requires a non-null argument}}
+  (void)__atomic_compare_exchange_n(p, NULL, val, 0, memory_order_relaxed, memory_order_relaxed); // expected-warning {{null passed to a callee that requires a non-null argument}}
+}