From bdf9e4656cff23b1d06ab5e5d4aac054c3472157 Mon Sep 17 00:00:00 2001
From: Artem Dergachev <artem.dergachev@gmail.com>
Date: Tue, 12 Dec 2017 02:59:09 +0000
Subject: [PATCH] [analyzer] StackAddrEscape: For now, disable the new async
escape checks.
The new check introduced in r318705 is useful, but suffers from a particular
class of false positives, namely, it does not account for
dispatch_barrier_sync() API which allows one to ensure that the asyncronously
executed block that captures a pointer to a local variable does not actually
outlive that variable.
The new check is split into a separate checker, under the name of
alpha.core.StackAddressAsyncEscape, which is likely to get enabled by default
again once these positives are fixed. The rest of the StackAddressEscapeChecker
is still enabled by default.
Differential Revision: https://reviews.llvm.org/D41042
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@320455 91177308-0d34-0410-b5e6-96231b3b80d8
---
.../clang/StaticAnalyzer/Checkers/Checkers.td | 4 +++
.../Checkers/StackAddrEscapeChecker.cpp | 27 ++++++++++++++++---
test/Analysis/stack-capture-leak-arc.mm | 16 ++++++++++-
test/Analysis/stack-capture-leak-no-arc.mm | 2 +-
4 files changed, 44 insertions(+), 5 deletions(-)
diff --git a/include/clang/StaticAnalyzer/Checkers/Checkers.td b/include/clang/StaticAnalyzer/Checkers/Checkers.td
index be8b1494c8..e510e84e93 100644
--- a/include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ b/include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -188,6 +188,10 @@ def DynamicTypeChecker : Checker<"DynamicTypeChecker">,
HelpText<"Check for cases where the dynamic and the static type of an object are unrelated.">,
DescFile<"DynamicTypeChecker.cpp">;
+def StackAddrAsyncEscapeChecker : Checker<"StackAddressAsyncEscape">,
+ HelpText<"Check that addresses to stack memory do not escape the function">,
+ DescFile<"StackAddrEscapeChecker.cpp">;
+
} // end "alpha.core"
let ParentPackage = Nullability in {
diff --git a/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp b/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
index 94cdd30680..25975628c5 100644
--- a/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
@@ -37,6 +37,14 @@ class StackAddrEscapeChecker
mutable std::unique_ptr<BuiltinBug> BT_capturedstackret;
public:
+ enum CheckKind {
+ CK_StackAddrEscapeChecker,
+ CK_StackAddrAsyncEscapeChecker,
+ CK_NumCheckKinds
+ };
+
+ DefaultBool ChecksEnabled[CK_NumCheckKinds];
+
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
void checkEndFunction(CheckerContext &Ctx) const;
@@ -225,6 +233,8 @@ void StackAddrEscapeChecker::checkReturnedBlockCaptures(
void StackAddrEscapeChecker::checkPreCall(const CallEvent &Call,
CheckerContext &C) const {
+ if (!ChecksEnabled[CK_StackAddrAsyncEscapeChecker])
+ return;
if (!Call.isGlobalCFunction("dispatch_after") &&
!Call.isGlobalCFunction("dispatch_async"))
return;
@@ -237,6 +247,8 @@ void StackAddrEscapeChecker::checkPreCall(const CallEvent &Call,
void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS,
CheckerContext &C) const {
+ if (!ChecksEnabled[CK_StackAddrEscapeChecker])
+ return;
const Expr *RetE = RS->getRetValue();
if (!RetE)
@@ -277,6 +289,9 @@ void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS,
}
void StackAddrEscapeChecker::checkEndFunction(CheckerContext &Ctx) const {
+ if (!ChecksEnabled[CK_StackAddrEscapeChecker])
+ return;
+
ProgramStateRef State = Ctx.getState();
// Iterate over all bindings to global variables and see if it contains
@@ -346,6 +361,12 @@ void StackAddrEscapeChecker::checkEndFunction(CheckerContext &Ctx) const {
}
}
-void ento::registerStackAddrEscapeChecker(CheckerManager &Mgr) {
- Mgr.registerChecker<StackAddrEscapeChecker>();
-}
+#define REGISTER_CHECKER(name) \
+ void ento::register##name(CheckerManager &Mgr) { \
+ StackAddrEscapeChecker *Chk = \
+ Mgr.registerChecker<StackAddrEscapeChecker>(); \
+ Chk->ChecksEnabled[StackAddrEscapeChecker::CK_##name] = true; \
+ }
+
+REGISTER_CHECKER(StackAddrEscapeChecker)
+REGISTER_CHECKER(StackAddrAsyncEscapeChecker)
diff --git a/test/Analysis/stack-capture-leak-arc.mm b/test/Analysis/stack-capture-leak-arc.mm
index 498f7e9b71..1ffee934c8 100644
--- a/test/Analysis/stack-capture-leak-arc.mm
+++ b/test/Analysis/stack-capture-leak-arc.mm
@@ -1,4 +1,4 @@
-// RUN: %clang_analyze_cc1 -triple x86_64-apple-darwin10 -analyzer-checker=core -fblocks -fobjc-arc -verify %s
+// RUN: %clang_analyze_cc1 -triple x86_64-apple-darwin10 -analyzer-checker=core,alpha.core.StackAddressAsyncEscape -fblocks -fobjc-arc -verify %s
typedef struct dispatch_queue_s *dispatch_queue_t;
typedef void (^dispatch_block_t)(void);
@@ -7,6 +7,7 @@ typedef long dispatch_once_t;
void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block);
typedef long dispatch_time_t;
void dispatch_after(dispatch_time_t when, dispatch_queue_t queue, dispatch_block_t block);
+void dispatch_barrier_sync(dispatch_queue_t queue, dispatch_block_t block);
extern dispatch_queue_t queue;
extern dispatch_once_t *predicate;
@@ -173,3 +174,16 @@ void test_no_leaks_on_semaphore_pattern() {
// Wait for the asynchronous work to finish
dispatch_semaphore_wait(semaphore, 1000);
}
+
+void test_dispatch_barrier_sync() {
+ int buf[16];
+ for (int n = 0; n < 16; ++n) {
+ int *ptr = &buf[n];
+ // FIXME: Should not warn. The dispatch_barrier_sync() call ensures
+ // that the block does not outlive 'buf'.
+ dispatch_async(queue, ^{ // expected-warning{{Address of stack memory associated with local variable 'buf' is captured by an asynchronously-executed block}}
+ (void)ptr;
+ });
+ }
+ dispatch_barrier_sync(queue, ^{});
+}
diff --git a/test/Analysis/stack-capture-leak-no-arc.mm b/test/Analysis/stack-capture-leak-no-arc.mm
index e14df09d55..33829f52e7 100644
--- a/test/Analysis/stack-capture-leak-no-arc.mm
+++ b/test/Analysis/stack-capture-leak-no-arc.mm
@@ -1,4 +1,4 @@
-// RUN: %clang_analyze_cc1 -triple x86_64-apple-darwin10 -analyzer-checker=core -fblocks -verify %s
+// RUN: %clang_analyze_cc1 -triple x86_64-apple-darwin10 -analyzer-checker=core,alpha.core.StackAddressAsyncEscape -fblocks -verify %s
typedef struct dispatch_queue_s *dispatch_queue_t;
typedef void (^dispatch_block_t)(void);
--
2.40.0