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[analyzer] Suppress "this" pointer escape during construction. 

Pointer escape event notifies checkers that a pointer can no longer be reliably
tracked by the analyzer. For example, if a pointer is passed into a function
that has no body available, or written into a global, MallocChecker would
no longer report memory leaks for such pointer.

In case of operator new() under -analyzer-config c++-allocator-inlining=true,
MallocChecker would start tracking the pointer allocated by operator new()
only to immediately meet a pointer escape event notifying the checker that the
pointer has escaped into a constructor (assuming that the body of the
constructor is not available) and immediately stop tracking it. Even though
it is theoretically possible for such constructor to put "this" into
a global container that would later be freed, we prefer to preserve the old
behavior of MallocChecker, i.e. a memory leak warning, in order to
be able to find any memory leaks in C++ at all. In fact, c++-allocator-inlining
*reduces* the amount of false positives coming from this-pointers escaping in
constructors, because it'd be able to inline constructors in some cases.

With other checkers working similarly, we simply suppress the escape event for
this-value of the constructor, regardless of analyzer options.

Differential Revision: https://reviews.llvm.org/D41797
rdar://problem/12180598

llvm-svn: 322795
This commit is contained in:
Artem Dergachev 2018-01-18 00:44:41 +00:00
parent 5e27cce467
commit 0c79eab03d
2 changed files with 8 additions and 2 deletions
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9
clang/lib/StaticAnalyzer/Core/CallEvent.cpp
View File

@ -672,8 +672,13 @@ SVal CXXConstructorCall::getCXXThisVal() const {
void CXXConstructorCall::getExtraInvalidatedValues(ValueList &Values,
RegionAndSymbolInvalidationTraits *ETraits) const {
if (Data)
Values.push_back(loc::MemRegionVal(static_cast<const MemRegion *>(Data)));
if (Data) {
loc::MemRegionVal MV(static_cast<const MemRegion *>(Data));
if (SymbolRef Sym = MV.getAsSymbol(true))
ETraits->setTrait(Sym,
RegionAndSymbolInvalidationTraits::TK_SuppressEscape);
Values.push_back(MV);
}
}
void CXXConstructorCall::getInitialStackFrameContents(

1
clang/test/Analysis/NewDeleteLeaks-PR19102.cpp
View File

@ -1,4 +1,5 @@
// RUN: %clang_analyze_cc1 -analyzer-checker=core,cplusplus.NewDeleteLeaks -verify %s
// RUN: %clang_analyze_cc1 -analyzer-checker=core,cplusplus.NewDeleteLeaks -analyzer-config c++-allocator-inlining=true -verify %s
class A0 {};