NoQ created this revision.
NoQ added reviewers: dcoughlin, xazax.hun, a.sidorin, george.karpenkov, szepet.
Herald added subscribers: cfe-commits, rnkovacs.
This is assertion removal that i find valid. With placement new (which isn't
even need to be inlined, we used to model it conservatively well enough),
anything of any type can have any dynamic type. Even if we have a concrete
region of a variable, its dynamic type and its static type can be completely
unrelated. This might be UB due to strict aliasing rules, but we shouldn't
crash. This patch introduces a relatively sane behavior in this scenario that
consists of `evalCast()`ing this-region to the assumed dynamic type during
virtual calls.
In the common case when the dynamic type is a sub-class of the static type,
this is worse than calling `attemptDownCast()` because it adds element region
instead of removing base regions (which is not incorrect but produces a
non-canonical representation of the SVal). But when the common-case approach is
known to have failed, there doesn't seem to be a better option.
A lot of these crashes have suddenly shown up when i was testing temporaries.
They have nothing to do with temporaries though, but with a weird
implementation detail of `std::function` that suddenly got some if its methods
inlined.
Repository:
rC Clang
https://reviews.llvm.org/D43659
Files:
lib/StaticAnalyzer/Core/CallEvent.cpp
test/Analysis/new-dynamic-types.cpp
Index: test/Analysis/new-dynamic-types.cpp
===================================================================
--- /dev/null
+++ test/Analysis/new-dynamic-types.cpp
@@ -0,0 +1,22 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -std=c++11 -verify %s
+
+// expected-no-diagnostics
+
+typedef __typeof(sizeof(int)) size_t;
+
+void *operator new(size_t size, void *ptr);
+
+struct B {
+ virtual void foo();
+};
+
+struct D : public B {
+ virtual void foo() override {}
+};
+
+void test() {
+ // FIXME: Potentially warn because this code is pretty weird.
+ B b;
+ new (&b) D;
+ b.foo(); // no-crash
+}
Index: lib/StaticAnalyzer/Core/CallEvent.cpp
===================================================================
--- lib/StaticAnalyzer/Core/CallEvent.cpp
+++ lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -583,11 +583,18 @@
ASTContext &Ctx = SVB.getContext();
const CXXRecordDecl *Class = MD->getParent();
QualType Ty = Ctx.getPointerType(Ctx.getRecordType(Class));
-
// FIXME: CallEvent maybe shouldn't be directly accessing StoreManager.
bool Failed;
ThisVal = StateMgr.getStoreManager().attemptDownCast(ThisVal, Ty,
Failed);
- assert(!Failed && "Calling an incorrectly devirtualized method");
+ if (Failed) {
+ // We might have suffered some sort of placement new earlier, so
+ // we're constructing in a completely unexpected storage.
+ // Fall back to a generic pointer cast for this-value.
+ const CXXMethodDecl *StaticMD = cast<CXXMethodDecl>(getDecl());
+ const CXXRecordDecl *StaticClass = StaticMD->getParent();
+ QualType StaticTy = Ctx.getPointerType(Ctx.getRecordType(StaticClass));
+ ThisVal = SVB.evalCast(ThisVal, Ty, StaticTy);
+ }
}
if (!ThisVal.isUnknown())
Index: test/Analysis/new-dynamic-types.cpp
===================================================================
--- /dev/null
+++ test/Analysis/new-dynamic-types.cpp
@@ -0,0 +1,22 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -std=c++11 -verify %s
+
+// expected-no-diagnostics
+
+typedef __typeof(sizeof(int)) size_t;
+
+void *operator new(size_t size, void *ptr);
+
+struct B {
+ virtual void foo();
+};
+
+struct D : public B {
+ virtual void foo() override {}
+};
+
+void test() {
+ // FIXME: Potentially warn because this code is pretty weird.
+ B b;
+ new (&b) D;
+ b.foo(); // no-crash
+}
Index: lib/StaticAnalyzer/Core/CallEvent.cpp
===================================================================
--- lib/StaticAnalyzer/Core/CallEvent.cpp
+++ lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -583,11 +583,18 @@
ASTContext &Ctx = SVB.getContext();
const CXXRecordDecl *Class = MD->getParent();
QualType Ty = Ctx.getPointerType(Ctx.getRecordType(Class));
-
// FIXME: CallEvent maybe shouldn't be directly accessing StoreManager.
bool Failed;
ThisVal = StateMgr.getStoreManager().attemptDownCast(ThisVal, Ty, Failed);
- assert(!Failed && "Calling an incorrectly devirtualized method");
+ if (Failed) {
+ // We might have suffered some sort of placement new earlier, so
+ // we're constructing in a completely unexpected storage.
+ // Fall back to a generic pointer cast for this-value.
+ const CXXMethodDecl *StaticMD = cast<CXXMethodDecl>(getDecl());
+ const CXXRecordDecl *StaticClass = StaticMD->getParent();
+ QualType StaticTy = Ctx.getPointerType(Ctx.getRecordType(StaticClass));
+ ThisVal = SVB.evalCast(ThisVal, Ty, StaticTy);
+ }
}
if (!ThisVal.isUnknown())
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