[Bug c++/81597] New: returns link to temporary value
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81597
Bug ID: 81597
Summary: returns link to temporary value
Product: gcc
Version: 4.8.5
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lisp2d at rambler dot ru
Target Milestone: ---
Functions returning C && , C const && , C const & from temporary object will
ALWAYS with wrong result.
Warning is good but ...
To do : prevent return rvalue from those functions.
example :
//> g++ -std=c++11 returntemp.cpp -o returntemp
#include
int && f ( ) {
return 1 ; }
int && g ( ) {
return 2 ; }
int const && ft ( ) {
return 7 ; }
int const && gt ( ) {
return 8 ; }
int const & fc ( ) {
return 5 ; }
int const & gc ( ) {
return 6 ; }
int fok ( ) {
return 3 ; }
int gok ( ) {
return 4 ; }
int main ( int , char * * ) {
std :: cout << "int &&" << std :: endl ;
{ int && x ( f ( ) ) ;
std :: cout << "x=" << x << std :: endl ;
int && y ( g ( ) ) ;
std :: cout << "y=" << y << std :: endl ;
std :: cout << "x=" << x << std :: endl ; }
std :: cout << "---" << std :: endl ;
std :: cout << "int const &&" << std :: endl ;
{ int const && x ( ft ( ) ) ;
std :: cout << "x=" << x << std :: endl ;
int const && y ( gt ( ) ) ;
std :: cout << "y=" << y << std :: endl ;
std :: cout << "x=" << x << std :: endl ; }
std :: cout << "---" << std :: endl ;
std :: cout << "int const &" << std :: endl ;
{ int const & x ( fc ( ) ) ;
std :: cout << "x=" << x << std :: endl ;
int const & y ( gc ( ) ) ;
std :: cout << "y=" << y << std :: endl ;
std :: cout << "x=" << x << std :: endl ; }
std :: cout << "---" << std :: endl ;
std :: cout << "int" << std :: endl ;
{ int && x ( fok ( ) ) ;
std :: cout << "x=" << x << std :: endl ;
int && y ( gok ( ) ) ;
std :: cout << "y=" << y << std :: endl ;
std :: cout << "x=" << x << std :: endl ; } }
result :
int &&
x=1
y=2
x=32621
---
int const &&
x=7
y=8
x=32621
---
int const &
x=5
y=6
x=32621
---
int
x=3
y=4
x=3
[Bug c++/81597] returns link to temporary value
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81597 --- Comment #2 from Lisp2D --- Make an error (don't compile) when returns rvalue from these functions. To forbid or banning.
[Bug c++/81597] returns link to temporary value
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81597 --- Comment #4 from Lisp2D --- -Werror=return-local-addr it is all i want thnx
[Bug c++/107132] New: a temporary object with an x-value is not destroyed and is bound to a variable
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107132
Bug ID: 107132
Summary: a temporary object with an x-value is not destroyed
and is bound to a variable
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lisp2d at rambler dot ru
Target Milestone: ---
a temporary object with an x-value is not destroyed and is bound to a variable
the question is taken from a social network
https://ru.stackoverflow.com/questions/1450260/Продление-времени-жизни-временного-объекта-в-присваивании/1450517#1450517
with tests
https://godbolt.org/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAMzwBtMA7AQwFtMQByARg9KtQYEAysib0QXACx8BBAKoBnTAAUAHpwAMvAFYTStJg1DIApACYAQuYukl9ZATwDKjdAGFUtAK4sGISQBspK4AMngMmAByPgBGmMQgAJykAA6oCoRODB7evv5BaRmOAmER0SxxCcl2mA5ZQgRMxAQ5Pn6Btpj2xQwNTQSlUbHxSbaNza15HQrjA%2BFDFSOJAJS2qF7EyOwc5gDM4cjeWADUJrtuTjPEmKxn2CYaAIIPj%2BEEx1hXXnUCCmdWTy%2BDmOj1OAHYLMcAH6PCDLY4MVCYVRbFLvEwQ06WayfAjEb49P67SEYgAi4NJ/xeLzexxYTHCcPBANBzJexw5xzQDBmIPMAWOTFOu3JzwhZOFooxVjBlOJ7M5M3QIBQ63R5zObixZlJmCBhOO4WOCjQKXYnI55jMwrcmo%2BerxBKyChtdrAOwArG4GO6qU8Lbj8T8eZLjho/ayyQqlSq0F51bbztrdfrncc1emqMbTeara6k4Gnb981rfV6fTt5U8yRxVrROB7eH4OFpSKhOLbsZZjetNpgsbseKQCJpa6sANb%2BRIAOkkc40AA4uBpEguwR6wbsgvWOJIm6O25xeAoQBph6PVnBYDBECBkbV4yRyJQmsAFMpDF0hAhUAB3ZtDmgLApHQTA9B%2BES0N%2Bf4AbwQEgfQCTAFwZhmKQ8F0PEADy8bQf%2BnBDveyCPMQb5HsEqi1A0%2BDNrw/CCCIYjsFIMiCIoKjqC2Oh6AYRgoNY1j6HgMQnpAqyoGizqcAAtEqZykqYXYWGYrYKL2Wx6Eq4QQV%2BP74dwvB4pg2xDr%2BxBMCkBG1voDb7lxh4cNglHII%2BxDHKoC4BNJASSMcwDIMgxwodO1oQJ2ViWKQxy4IQJADlwyyGReqwIDcWAJHCNm7rwLAgLsuzTokGiBIkuylQEGgelwVUeqQzatu2HDHqe55cZeN4QEgRGuc%2BECvu%2Bn5QXpsHoagwGgeBg14SNGGISgvHAAA%2Bo6DDjqN42IThwjDVZFG1CRZFNXtyDUeE5H0cIojiCxF3sWoB66GhC38UpQkifA4mSb8MlySKikRcpqnqcxYw0TpQ0wbtRkmbwZkWVZda2XVB6NU5D5EG5HleT5XILccEAreO8JhQJkXRfgGPxYlrVaMsKVpSMmU7nupC5YOs5gmYYJcFwARgpViQBLs0j1bwjXNWeI5taQV63t1GO9f14PTbts1gVkys7QZ60ISMABuyApCki161wiSLQYBAOotqg%2BTrmHEFtKva0RB0nkdRGnbRrGXUxEjSLdSj3fZui7PohjGKTNi0MJomZRJhKcAA9DG/3WCpx7A5pBBg1NWtDtDu1w5ZBmIxwjbI/ZqPOa57k4ywCgG8cpszpbDr4%2BFgnk7Fbl7AlSVtfTTDpZQZcs2zkjTgEqEeokkhlflHpmFItWiw5Es02OpCTh6GjTh6B%2BJFwC5FShkhmAEtU7rsdkNeRUu02XZi32L9/JaQevxBkziSEAA%3D
#include
int destructions;
struct A { ~A() noexcept { ++destructions; } };
int main() {
{
const A& a = A{} = A{};
std::cout << "Destructions in scope: " << destructions << '\n';
destructions = 0;
}
std::cout << "Destructions out of scope: " << destructions << '\n';
}
the object under variable a should be dead. But it's still alive.
[Bug c++/109529] New: the r-value volatile object is not accepted by the l-value volatile constant argument.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109529
Bug ID: 109529
Summary: the r-value volatile object is not accepted by the
l-value volatile constant argument.
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lisp2d at rambler dot ru
Target Milestone: ---
void funy(int const &){}
void fun(int volatile const &){}
int main(){
int y ;
funy(y); // good
funy(static_cast(y)); // good
funy(static_cast(y)); // good
int volatile x ;
fun(x); // good
fun(static_cast(x)); // error
fun(static_cast(x)); // error
}
[Bug c++/109529] the r-value volatile object is not accepted by the l-value volatile constant argument.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109529 --- Comment #3 from Lisp2D --- (In reply to Andrew Pinski from comment #2) > Since `static_cast(x)` is considered rvalue and `int I can't find a reason anywhere in the standard why the volatile property prevents conversion from `&&` to `const &`.
[Bug c++/109529] the r-value volatile object is not accepted by the l-value volatile constant argument.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109529 --- Comment #6 from Lisp2D --- (In reply to Andrew Pinski from comment #4) > https://stackoverflow.com/questions/40193008/why-a-const-volatile-reference- stackoverflow offers to link an rvalue reference to a variable for this. But I think this is historical stupidity. int volatile && rx = static_cast < int volatile && > ( x ) ; int volatile const & lx = rx ; fun(lx);
[Bug c++/109529] the r-value volatile object is not accepted by the l-value volatile constant argument.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109529 --- Comment #7 from Lisp2D --- .. or int volatile && rx = static_cast < int volatile && > ( x ) ; fun(rx);
