[clang] [alpha.webkit.UnretainedCallArgsChecker] Treat NSStringFromSelector and alike as trivial and returns a retained value (PR #161135)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-static-analyzer-1

Author: Ryosuke Niwa (rniwa)

<details>
<summary>Changes</summary>

Treat NSStringFromSelector, NSSelectorFromString, NSStringFromClass, NSClassFromString, NSStringFromProtocol, and NSProtocolFromString as trivial, and treat their return values as a safe pointer origin since the return value of these functions don't need to be retained.

---
Full diff: https://github.com/llvm/llvm-project/pull/161135.diff


3 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp (+5-1) 
- (modified) clang/test/Analysis/Checkers/WebKit/objc-mock-types.h (+9) 
- (modified) clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm (+18) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp
index 00a1b8b6e7e89..5b8c9b2d8fcf8 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp
@@ -158,7 +158,9 @@ bool tryToFindPtrOrigin(
 
         auto Name = safeGetName(callee);
         if (Name == "__builtin___CFStringMakeConstantString" ||
-            Name == "NSClassFromString")
+            Name == "NSStringFromSelector" || Name == "NSSelectorFromString" ||
+            Name == "NSStringFromClass" || Name == "NSClassFromString" ||
+            Name == "NSStringFromProtocol" || Name == "NSProtocolFromString")
           return callback(E, true);
       } else if (auto *CalleeE = call->getCallee()) {
         if (auto *E = dyn_cast<DeclRefExpr>(CalleeE->IgnoreParenCasts())) {
@@ -196,6 +198,8 @@ bool tryToFindPtrOrigin(
           !Selector.getNumArgs())
         return callback(E, true);
     }
+    if (auto *ObjCProtocol = dyn_cast<ObjCProtocolExpr>(E))
+      return callback(ObjCProtocol, true);
     if (auto *ObjCDict = dyn_cast<ObjCDictionaryLiteral>(E))
       return callback(ObjCDict, true);
     if (auto *ObjCArray = dyn_cast<ObjCArrayLiteral>(E))
diff --git a/clang/test/Analysis/Checkers/WebKit/objc-mock-types.h b/clang/test/Analysis/Checkers/WebKit/objc-mock-types.h
index 39dee1746158b..8c3c6b78193dc 100644
--- a/clang/test/Analysis/Checkers/WebKit/objc-mock-types.h
+++ b/clang/test/Analysis/Checkers/WebKit/objc-mock-types.h
@@ -84,6 +84,15 @@ typedef CVImageBufferRef CVPixelBufferRef;
 typedef signed int CVReturn;
 CVReturn CVPixelBufferCreateWithIOSurface(CFAllocatorRef allocator, IOSurfaceRef surface, CFDictionaryRef pixelBufferAttributes, CF_RETURNS_RETAINED CVPixelBufferRef * pixelBufferOut);
 
+extern "C" NSString *NSStringFromSelector(SEL aSelector);
+extern "C" SEL NSSelectorFromString(NSString *aSelectorName);
+
+extern "C" NSString *NSStringFromClass(Class aClass);
+extern "C" Class NSClassFromString(NSString *aClassName);
+
+extern "C" NSString *NSStringFromProtocol(Protocol *proto);
+extern "C" Protocol * NSProtocolFromString(NSString *namestr);
+
 CFRunLoopRef CFRunLoopGetCurrent(void);
 CFRunLoopRef CFRunLoopGetMain(void);
 extern CFTypeRef CFRetain(CFTypeRef cf);
diff --git a/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm b/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm
index c9d2fe861bb49..a78536cd77d41 100644
--- a/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm
+++ b/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm
@@ -561,6 +561,24 @@ void foo() {
 
 } // namespace ns_retained_return_value
 
+namespace sel_string {
+
+void consumeStr(NSString *);
+void consumeSel(SEL);
+void consumeClass(Class);
+void consumeProtocol(Protocol *);
+
+void foo() {
+  consumeStr(NSStringFromSelector(@selector(mutableCopy)));
+  consumeSel(NSSelectorFromString(@"mutableCopy"));
+  consumeStr(NSStringFromClass(NSNumber.class));
+  consumeClass(NSClassFromString(@"NSNumber"));
+  consumeStr(NSStringFromProtocol(@protocol(NSCopying)));
+  consumeProtocol(NSProtocolFromString(@"NSCopying"));
+}
+
+} // namespace sel_string
+
 @interface TestObject : NSObject
 - (void)doWork:(NSString *)msg, ...;
 - (void)doWorkOnSelf;

``````````

</details>


https://github.com/llvm/llvm-project/pull/161135