[analyzer] DeallocChecker: Don't warn about directly-set IBOutlet ivars on macOS

On macOS (but not iOS), if an ObjC property has no setter, the nib-loading code
for an IBOutlet is documented as directly setting the backing ivar without
retaining the value -- even if the property is 'retain'.

This resulted in false positives from the DeallocChecker for code that did not
release such ivars in -dealloc.

To avoid these false positives, treat IBOutlet ivars that back a property
without a setter as having an unknown release requirement in macOS.

rdar://problem/28507353

llvm-svn: 284084

1 files changed, 31 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/CheckObjCDealloc.cpp b/clang/lib/StaticAnalyzer/Checkers/CheckObjCDealloc.cpp
index 4fece1c7fff..1c8ca0f4295 100644
--- a/clang/lib/StaticAnalyzer/Checkers/CheckObjCDealloc.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/CheckObjCDealloc.cpp
@@ -34,6 +34,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/Basic/LangOptions.h"
+#include "clang/Basic/TargetInfo.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
@@ -180,6 +181,7 @@ private:
   bool classHasSeparateTeardown(const ObjCInterfaceDecl *ID) const;
 
   bool isReleasedByCIFilterDealloc(const ObjCPropertyImplDecl *PropImpl) const;
+  bool isNibLoadedIvarWithoutRetain(const ObjCPropertyImplDecl *PropImpl) const;
 };
 } // End anonymous namespace.
 
@@ -935,6 +937,9 @@ ReleaseRequirement ObjCDeallocChecker::getDeallocReleaseRequirement(
     if (isReleasedByCIFilterDealloc(PropImpl))
       return ReleaseRequirement::MustNotReleaseDirectly;
 
+    if (isNibLoadedIvarWithoutRetain(PropImpl))
+      return ReleaseRequirement::Unknown;
+
     return ReleaseRequirement::MustRelease;
 
   case ObjCPropertyDecl::Weak:
@@ -1091,6 +1096,32 @@ bool ObjCDeallocChecker::isReleasedByCIFilterDealloc(
   return false;
 }
 
+/// Returns whether the ivar backing the property is an IBOutlet that
+/// has its value set by nib loading code without retaining the value.
+///
+/// On macOS, if there is no setter, the nib-loading code sets the ivar
+/// directly, without retaining the value,
+///
+/// On iOS and its derivatives, the nib-loading code will call
+/// -setValue:forKey:, which retains the value before directly setting the ivar.
+bool ObjCDeallocChecker::isNibLoadedIvarWithoutRetain(
+    const ObjCPropertyImplDecl *PropImpl) const {
+  const ObjCIvarDecl *IvarDecl = PropImpl->getPropertyIvarDecl();
+  if (!IvarDecl->hasAttr<IBOutletAttr>())
+    return false;
+
+  const llvm::Triple &Target =
+      IvarDecl->getASTContext().getTargetInfo().getTriple();
+
+  if (!Target.isMacOSX())
+    return false;
+
+  if (PropImpl->getPropertyDecl()->getSetterMethodDecl())
+    return false;
+
+  return true;
+}
+
 void ento::registerObjCDeallocChecker(CheckerManager &Mgr) {
   const LangOptions &LangOpts = Mgr.getLangOpts();
   // These checker only makes sense under MRR.