Fix warning on unused return values in RCTSRWebSocket

Summary:
Assert that the return value of these methods is sane.

Closes https://github.com/facebook/react-native/issues/8108

Reviewed By: majak

Differential Revision: D3722629

fbshipit-source-id: 2a67daae6dc380721e5dad27acd2ab67f71d0c6c

Libraries/LinkingIOS/RCTLinking.xcodeproj/project.pbxproj

@@ -157,6 +157,10 @@
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = iphoneos;
+				WARNING_CFLAGS = (
+					"-Werror",
+					"-Wall",
+				);
 			};
 			name = Debug;
 		};
@@ -192,6 +196,10 @@
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
 				VALIDATE_PRODUCT = YES;
+				WARNING_CFLAGS = (
+					"-Werror",
+					"-Wall",
+				);
 			};
 			name = Release;
 		};

Libraries/WebSocket/RCTSRWebSocket.m

@@ -491,7 +491,8 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   CFHTTPMessageSetHeaderFieldValue(request, CFSTR("Host"), (__bridge CFStringRef)(_url.port ? [NSString stringWithFormat:@"%@:%@", _url.host, _url.port] : _url.host));
 
   NSMutableData *keyBytes = [[NSMutableData alloc] initWithLength:16];
-  SecRandomCopyBytes(kSecRandomDefault, keyBytes.length, keyBytes.mutableBytes);
+  int result = SecRandomCopyBytes(kSecRandomDefault, keyBytes.length, keyBytes.mutableBytes);
+  assert(result == 0);
   _secKey = [keyBytes base64EncodedStringWithOptions:0];
   assert([_secKey length] == 24);
 
@@ -1331,7 +1332,8 @@ static const size_t RCTSRFrameHeaderOverhead = 32;
     }
   } else {
     uint8_t *mask_key = frame_buffer + frame_buffer_size;
-    SecRandomCopyBytes(kSecRandomDefault, sizeof(uint32_t), (uint8_t *)mask_key);
+    int result = SecRandomCopyBytes(kSecRandomDefault, sizeof(uint32_t), (uint8_t *)mask_key);
+    assert(result == 0);
     frame_buffer_size += sizeof(uint32_t);
 
     // TODO: could probably optimize this with SIMD