[PATCH] D63956: [analyzer] NonnullGlobalConstants: Don't be confused with a _Nonnull attribute.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ created this revision.
NoQ added a reviewer: dcoughlin.
Herald added subscribers: cfe-commits, Charusso, dkrupp, donat.nagy, Szelethus, mikhail.ramalho, a.sidorin, szepet, baloghadamsoftware, xazax.hun.
Herald added a project: clang.

The NonnullGlobalConstants checker models the rule "it doesn't make sense to make a constant global pointer and initialize it to null"; it makes sure that whatever it's initialized with is known to be non-null.

Ironically, annotating the type of the pointer as `_Nonnull` breaks the checker.

Fix handling of the `_Nonnull` annotation so that it was instead one more reason to believe that the value is non-null.


Repository:
  rC Clang

https://reviews.llvm.org/D63956

Files:
  clang/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp
  clang/test/Analysis/nonnull-global-constants.mm


Index: clang/test/Analysis/nonnull-global-constants.mm
===================================================================
--- clang/test/Analysis/nonnull-global-constants.mm
+++ clang/test/Analysis/nonnull-global-constants.mm
@@ -101,3 +101,15 @@
 void testNonnullNonconstBool() {
   clang_analyzer_eval(kBoolMutable); // expected-warning{{UNKNOWN}}
 }
+
+// If it's annotated as nonnull, it doesn't even need to be const.
+extern CFStringRef _Nonnull str3;
+void testNonnullNonconstCFString() {
+  clang_analyzer_eval(str3); // expected-warning{{TRUE}}
+}
+
+// This one's nonnull for two reasons.
+extern const CFStringRef _Nonnull str4;
+void testNonnullNonnullCFString() {
+  clang_analyzer_eval(str4); // expected-warning{{TRUE}}
+}
Index: clang/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp
@@ -106,14 +106,21 @@
     return true;
 
   // Look through the typedefs.
-  while (auto *T = dyn_cast<TypedefType>(Ty)) {
-    Ty = T->getDecl()->getUnderlyingType();
-
-    // It is sufficient for any intermediate typedef
-    // to be classified const.
-    HasConst = HasConst || Ty.isConstQualified();
-    if (isNonnullType(Ty) && HasConst)
-      return true;
+  while (const Type *T = Ty.getTypePtr()) {
+    if (const auto *TT = dyn_cast<TypedefType>(T)) {
+      Ty = TT->getDecl()->getUnderlyingType();
+      // It is sufficient for any intermediate typedef
+      // to be classified const.
+      HasConst = HasConst || Ty.isConstQualified();
+      if (isNonnullType(Ty) && HasConst)
+        return true;
+    } else if (const auto *AT = dyn_cast<AttributedType>(T)) {
+      if (AT->getAttrKind() == attr::TypeNonNull)
+        return true;
+      Ty = AT->getModifiedType();
+    } else {
+      return false;
+    }
   }
   return false;
 }


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