Hi Gabor,
this makes clang warn on this program:
$ cat test.cc
#include <algorithm>
#include <vector>
struct S {
bool operator==(const S &rhs) const;
};
const S &f(const std::vector<S> &v) {
const auto &it = std::find(v.rbegin(), v.rend(), S());
return *it;
}
$ out/gn/bin/clang -c test.cc -isysroot $(xcrun -show-sdk-path) -isystem
libcxx/include/ -Wall
test.cc:10:11: warning: returning reference to local temporary object
[-Wreturn-stack-address]
return *it;
^~
test.cc:9:15: note: binding reference variable 'it' here
const auto &it = std::find(v.rbegin(), v.rend(), S());
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
Is the warning correct here? The `const auto &it` is lifetime-extended to
the end of the block, and *it should return a reference to an element in
the vector. Since the vector's passed in, this should be fine. Or am I
missing something?
Thanks,
Nico
On Fri, Aug 9, 2019 at 11:15 AM Gabor Horvath via cfe-commits <
cfe-commits@lists.llvm.org> wrote:
> Author: xazax
> Date: Fri Aug 9 08:16:35 2019
> New Revision: 368446
>
> URL: http://llvm.org/viewvc/llvm-project?rev=368446&view=rev
> Log:
> More warnings regarding gsl::Pointer and gsl::Owner attributes
>
> Differential Revision: https://reviews.llvm.org/D65120
>
> Modified:
> cfe/trunk/lib/Sema/SemaInit.cpp
> cfe/trunk/test/Analysis/inner-pointer.cpp
> cfe/trunk/test/Sema/warn-lifetime-analysis-nocfg.cpp
>
> Modified: cfe/trunk/lib/Sema/SemaInit.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=368446&r1=368445&r2=368446&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaInit.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Aug 9 08:16:35 2019
> @@ -6564,6 +6564,25 @@ template <typename T> static bool isReco
> return false;
> }
>
> +static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
> + if (auto *Conv = dyn_cast_or_null<CXXConversionDecl>(Callee))
> + if (isRecordWithAttr<PointerAttr>(Conv->getConversionType()))
> + return true;
> + if (!Callee->getParent()->isInStdNamespace() ||
> !Callee->getIdentifier())
> + return false;
> + if (!isRecordWithAttr<PointerAttr>(Callee->getThisObjectType()) &&
> + !isRecordWithAttr<OwnerAttr>(Callee->getThisObjectType()))
> + return false;
> + if (!isRecordWithAttr<PointerAttr>(Callee->getReturnType()) &&
> + !Callee->getReturnType()->isPointerType())
> + return false;
> + return llvm::StringSwitch<bool>(Callee->getName())
> + .Cases("begin", "rbegin", "cbegin", "crbegin", true)
> + .Cases("end", "rend", "cend", "crend", true)
> + .Cases("c_str", "data", "get", true)
> + .Default(false);
> +}
> +
> static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
> LocalVisitor Visit) {
> auto VisitPointerArg = [&](const Decl *D, Expr *Arg) {
> @@ -6577,10 +6596,9 @@ static void handleGslAnnotatedTypes(Indi
> };
>
> if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {
> - const FunctionDecl *Callee = MCE->getDirectCallee();
> - if (auto *Conv = dyn_cast_or_null<CXXConversionDecl>(Callee))
> - if (isRecordWithAttr<PointerAttr>(Conv->getConversionType()))
> - VisitPointerArg(Callee, MCE->getImplicitObjectArgument());
> + const auto *MD = cast_or_null<CXXMethodDecl>(MCE->getDirectCallee());
> + if (MD && shouldTrackImplicitObjectArg(MD))
> + VisitPointerArg(MD, MCE->getImplicitObjectArgument());
> return;
> }
>
>
> Modified: cfe/trunk/test/Analysis/inner-pointer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/inner-pointer.cpp?rev=368446&r1=368445&r2=368446&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/Analysis/inner-pointer.cpp (original)
> +++ cfe/trunk/test/Analysis/inner-pointer.cpp Fri Aug 9 08:16:35 2019
> @@ -1,4 +1,5 @@
> -// RUN: %clang_analyze_cc1 -analyzer-checker=cplusplus.InnerPointer \
> +// RUN: %clang_analyze_cc1 -analyzer-checker=cplusplus.InnerPointer \
> +// RUN: -Wno-dangling -Wno-dangling-field -Wno-return-stack-address \
> // RUN: %s -analyzer-output=text -verify
>
> #include "Inputs/system-header-simulator-cxx.h"
>
> Modified: cfe/trunk/test/Sema/warn-lifetime-analysis-nocfg.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/warn-lifetime-analysis-nocfg.cpp?rev=368446&r1=368445&r2=368446&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/Sema/warn-lifetime-analysis-nocfg.cpp (original)
> +++ cfe/trunk/test/Sema/warn-lifetime-analysis-nocfg.cpp Fri Aug 9
> 08:16:35 2019
> @@ -2,7 +2,6 @@
> struct [[gsl::Owner(int)]] MyIntOwner {
> MyIntOwner();
> int &operator*();
> - int *c_str() const;
> };
>
> struct [[gsl::Pointer(int)]] MyIntPointer {
> @@ -52,16 +51,6 @@ long *ownershipTransferToRawPointer() {
> return t.releaseAsRawPointer(); // ok
> }
>
> -int *danglingRawPtrFromLocal() {
> - MyIntOwner t;
> - return t.c_str(); // TODO
> -}
> -
> -int *danglingRawPtrFromTemp() {
> - MyIntPointer p;
> - return p.toOwner().c_str(); // TODO
> -}
> -
> struct Y {
> int a[4];
> };
> @@ -103,6 +92,12 @@ MyIntPointer danglingGslPtrFromTemporary
> return MyIntOwner{}; // expected-warning {{returning address of local
> temporary object}}
> }
>
> +MyIntOwner makeTempOwner();
> +
> +MyIntPointer danglingGslPtrFromTemporary2() {
> + return makeTempOwner(); // expected-warning {{returning address of
> local temporary object}}
> +}
> +
> MyLongPointerFromConversion danglingGslPtrFromTemporaryConv() {
> return MyLongOwnerWithConversion{}; // expected-warning {{returning
> address of local temporary object}}
> }
> @@ -124,12 +119,52 @@ void initLocalGslPtrWithTempOwner() {
> global2 = MyLongOwnerWithConversion{}; // TODO ?
> }
>
> -struct IntVector {
> - int *begin();
> - int *end();
> +namespace std {
> +template <typename T>
> +struct basic_iterator {};
> +
> +template <typename T>
> +struct vector {
> + typedef basic_iterator<T> iterator;
> + iterator begin();
> + T *data();
> +};
> +
> +template<typename T>
> +struct basic_string {
> + const T *c_str() const;
> +};
> +
> +template<typename T>
> +struct unique_ptr {
> + T *get() const;
> };
> +}
>
> void modelIterators() {
> - int *it = IntVector{}.begin(); // TODO ?
> + std::vector<int>::iterator it = std::vector<int>().begin(); //
> expected-warning {{object backing the pointer will be destroyed at the end
> of the full-expression}}
> (void)it;
> }
> +
> +std::vector<int>::iterator modelIteratorReturn() {
> + return std::vector<int>().begin(); // expected-warning {{returning
> address of local temporary object}}
> +}
> +
> +const char *danglingRawPtrFromLocal() {
> + std::basic_string<char> s;
> + return s.c_str(); // expected-warning {{address of stack memory
> associated with local variable 's' returned}}
> +}
> +
> +const char *danglingRawPtrFromTemp() {
> + return std::basic_string<char>().c_str(); // expected-warning
> {{returning address of local temporary object}}
> +}
> +
> +std::unique_ptr<int> getUniquePtr();
> +
> +int *danglingUniquePtrFromTemp() {
> + return getUniquePtr().get(); // expected-warning {{returning address of
> local temporary object}}
> +}
> +
> +int *danglingUniquePtrFromTemp2() {
> + return std::unique_ptr<int>().get(); // expected-warning {{returning
> address of local temporary object}}
> +}
>
>
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> cfe-commits@lists.llvm.org
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>
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