New Infer rule for dispatch_once_t

Reviewed By: martintrojer

Differential Revision: D12888401

fbshipit-source-id: 1c4af8922

infer/lib/linter_rules/linters.al

@@ -267,3 +267,16 @@ DEFINE-CHECKER DISCOURAGED_WEAK_PROPERTY_CUSTOM_SETTER = {
   SET severity = "WARNING";
   SET mode = "OFF";
 };
+
+DEFINE-CHECKER WRONG_SCOPE_FOR_DISPATCH_ONCE_T = {
+
+  SET report_when =
+	    WHEN
+			  NOT (is_global_var() OR is_static_local_var()) AND
+				has_type("dispatch_once_t")
+			HOLDS-IN-NODE VarDecl;
+
+		SET message = "Variables of type dispatch_once_t must have global or static scope. The result of using this type with automatic or dynamic allocation is undefined.";
+		SET severity = "WARNING";
+		SET mode = "OFF";
+};

infer/tests/codetoanalyze/objc/linters/dispatch.m

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2018-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+#import <Foundation/Foundation.h>
+
+@interface A : NSObject
+@end
+
+@implementation A
+
++ (instancetype)sharedInstanceOK {
+  static id _sharedInstance = nil;
+  static dispatch_once_t onceTokenA;
+  dispatch_once(&onceTokenA, ^{
+    _sharedInstance = [[self alloc] init];
+  });
+
+  return _sharedInstance;
+}
+
+@end
+
+@interface B : NSObject
+@end
+
+@implementation B
+
++ (instancetype)sharedInstanceBAD {
+  static id _sharedInstance = nil;
+  dispatch_once_t onceTokenB;
+  dispatch_once(&onceTokenB, ^{
+    _sharedInstance = [[self alloc] init];
+  });
+
+  return _sharedInstance;
+}
+
+@end

infer/tests/codetoanalyze/objc/linters/issues.exp

@@ -30,6 +30,7 @@ codetoanalyze/objc/linters/badpointer.m, bad5, 97, BAD_POINTER_COMPARISON, no_bu
 codetoanalyze/objc/linters/badpointer.m, bad6, 104, BAD_POINTER_COMPARISON, no_bucket, WARNING, []
 codetoanalyze/objc/linters/badpointer.m, bad8, 119, BAD_POINTER_COMPARISON, no_bucket, WARNING, []
 codetoanalyze/objc/linters/badpointer.m, bad9, 126, BAD_POINTER_COMPARISON, no_bucket, WARNING, []
+codetoanalyze/objc/linters/dispatch.m, B_sharedInstanceBAD, 33, WRONG_SCOPE_FOR_DISPATCH_ONCE_T, no_bucket, WARNING, []
 codetoanalyze/objc/linters/implicit_cast.m, Implicit_cast_call_with_boxed_int, 67, POINTER_TO_INTEGRAL_IMPLICIT_CAST, no_bucket, WARNING, []
 codetoanalyze/objc/linters/implicit_cast.m, Implicit_cast_call_with_string, 60, POINTER_TO_INTEGRAL_IMPLICIT_CAST, no_bucket, WARNING, []
 codetoanalyze/objc/linters/implicit_cast.m, Implicit_cast_ivar_dictionary_item_call_funct_with_int, 45, POINTER_TO_INTEGRAL_IMPLICIT_CAST, no_bucket, WARNING, []