xazax.hun created this revision.
Herald added subscribers: whisperity, mgorny.
I added a checker to model builtin functions. Only one builtin function is
modelled so far. The motivation behind using `__builtin_assume` from the
analyzers point of view is to add assumptions. The conventional way to express
invariants is to use asserts (with correct annotations for noreturn functions).
However on some platform the users do not want to pay the price of an assert,
even in the debug build (especially in a hot code). This way we can express
these invariants to the analyzer without runtime overhead.
What do you think?
Repository:
rL LLVM
https://reviews.llvm.org/D33092
Files:
include/clang/StaticAnalyzer/Checkers/Checkers.td
lib/StaticAnalyzer/Checkers/CMakeLists.txt
lib/StaticAnalyzer/Checkers/ModelBuiltinChecker.cpp
test/Analysis/builtin-assume.c
Index: test/Analysis/builtin-assume.c
===================================================================
--- /dev/null
+++ test/Analysis/builtin-assume.c
@@ -0,0 +1,8 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify %s
+
+void clang_analyzer_eval(int);
+
+void f(int i) {
+ __builtin_assume(i < 10);
+ clang_analyzer_eval(i < 15); // expected-warning {{TRUE}}
+}
Index: lib/StaticAnalyzer/Checkers/ModelBuiltinChecker.cpp
===================================================================
--- /dev/null
+++ lib/StaticAnalyzer/Checkers/ModelBuiltinChecker.cpp
@@ -0,0 +1,59 @@
+//=== ModelBuiltinChecker.cpp --------- Model builtin functions -*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This checker improves modeling of a few builtin compiler functions.
+// It does not generate warnings.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+
+using namespace clang;
+using namespace clang::ento;
+
+namespace {
+class ModelBuiltinsChecker : public Checker<eval::Call> {
+public:
+ bool evalCall(const CallExpr *CE, CheckerContext &C) const {
+ const FunctionDecl *FD =
+ dyn_cast_or_null<FunctionDecl>(CE->getCalleeDecl());
+ if (!FD)
+ return false;
+ if (!FD->getIdentifier())
+ return false;
+
+ StringRef Name = FD->getName();
+ if (Name.empty() || !C.isCLibraryFunction(FD, Name) ||
+ Name != "__builtin_assume")
+ return false;
+
+ ProgramStateRef State = C.getState();
+ const LocationContext *LC = C.getLocationContext();
+ SVal ArgSVal = State->getSVal(CE->getArg(0), LC);
+ if (ArgSVal.isUndef())
+ return false;
+
+ State = State->assume(ArgSVal.castAs<DefinedOrUnknownSVal>(), true);
+ // FIXME: do we want to warn here?
+ if (!State)
+ return false;
+
+ C.addTransition(State);
+ return true;
+ }
+};
+} // end of anonymous namespace
+
+void ento::registerModelBuiltinsChecker(CheckerManager &mgr) {
+ mgr.registerChecker<ModelBuiltinsChecker>();
+}
Index: lib/StaticAnalyzer/Checkers/CMakeLists.txt
===================================================================
--- lib/StaticAnalyzer/Checkers/CMakeLists.txt
+++ lib/StaticAnalyzer/Checkers/CMakeLists.txt
@@ -49,6 +49,7 @@
MallocOverflowSecurityChecker.cpp
MallocSizeofChecker.cpp
MisusedMovedObjectChecker.cpp
+ ModelBuiltinChecker.cpp
MPI-Checker/MPIBugReporter.cpp
MPI-Checker/MPIChecker.cpp
MPI-Checker/MPIFunctionClassifier.cpp
Index: include/clang/StaticAnalyzer/Checkers/Checkers.td
===================================================================
--- include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -99,6 +99,10 @@
HelpText<"Check for dereferences of null pointers">,
DescFile<"DereferenceChecker.cpp">;
+def ModelBuiltinsChecker : Checker<"ModelBuiltins">,
+ HelpText<"Model some compiler builtin functions">,
+ DescFile<"ModelBuiltinChecker.cpp">;
+
def CallAndMessageChecker : Checker<"CallAndMessage">,
HelpText<"Check for logical errors for function calls and Objective-C message expressions (e.g., uninitialized arguments, null function pointers)">,
DescFile<"CallAndMessageChecker.cpp">;
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