[Bug c++/81042] Too many constexpr iterations on unreachable loop.

[ralph.tandetzky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81042

Ralph Tandetzky  changed:

   What|Removed |Added

 CC||ralph.tandetzky at gmail dot 
com

--- Comment #4 from Ralph Tandetzky  ---
The following code:

 1 constexpr int f()
 2 {
 3 for ( int i = 0; i < 1; ++i ) {
 4 const int digit = i/1;
 5 if( digit == 0 )
 6 continue;
 7 for ( int j = 0; j < 0; ++j ) {} // <-- loop iteration count
 8  // exceeds limit
 9 }
10 return 0;
11 }
12
13 constexpr int i = f();

produces the following error with GCC 8.2:

:13:20:   in 'constexpr' expansion of 'f()'

:7:9: error: 'constexpr' loop iteration count exceeds 
limit of 262144 (use -fconstexpr-loop-limit= to increase the limit)

 for ( int j = 0; j < 0; ++j ) {}
 ^~~

[Bug libstdc++/77322] New: [C++11] std::function::swap should be noexcept.

[ralph.tandetzky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77322

Bug ID: 77322
   Summary: [C++11] std::function::swap should be noexcept.
   Product: gcc
   Version: 6.1.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: libstdc++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: ralph.tandetzky at gmail dot com
  Target Milestone: ---

The C++11, C++14 and C++17 standard require, that
std::function::swap() be noexcept. However, the following program
does not compile:

#include 

int main()
{
std::function<void()> f;
static_assert( noexcept( f.swap(f) ), "" );
}

This is the error message:

main.cpp: In function 'int main()':
main.cpp:6:5: error: static assertion failed
 static_assert( noexcept( f.swap(f) ), "" );
 ^

By the way, clang does it right. This bug should be very simple to fix. This
concerns all GCC versions that support C++11 from version 4.7 (or maybe
earlier) until 6.1 (or maybe later).

[Bug c++/68071] Generic lambda variadic argument pack cannot be empty

[ralph.tandetzky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68071

Ralph Tandetzky  changed:

   What|Removed |Added

 CC||ralph.tandetzky at gmail dot 
com

--- Comment #2 from Ralph Tandetzky  ---
I can confirm that error. The code 

int main(){
[](auto...){}();
}

leads to the following compile-time error:

main.cpp: In function 'int main()':
main.cpp:2:23: error: no match for call to '(main()::<lambda(auto:1, ...)>)
()'
 [](auto...){}();
   ^
main.cpp:2:19: note: candidate: template
main()::<lambda(auto:1, ...)>
 [](auto...){}();
   ^
main.cpp:2:19: note:   template argument deduction/substitution failed:
main.cpp:2:23: note:   candidate expects 1 argument, 0 provided
 [](auto...){}();
   ^

This is the case for gcc 4.9 and gcc 5.2 with C++14 enabled. Clang 3.6 compiles
it.

[Bug c++/68309] New: [C++14] Expanding a captured parameter pack with std::forward<decltype(args)>(args) fails.

[ralph.tandetzky at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68309

Bug ID: 68309
   Summary: [C++14] Expanding a captured parameter pack with
std::forward<decltype(args)>(args) fails.
   Product: gcc
   Version: 4.9.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: ralph.tandetzky at gmail dot com
  Target Milestone: ---

Here's a minimal not-working example:

#include 

using namespace std;

template 
void print( Ts &&... args )
{
[&]
{
const auto _ = { 
((cout << forward<decltype(args)>(args) << endl),0)... };
(void)_;
}();
}

int main()
{
print( 1, "blub", std::to_string(3.1415), 4, 5.2 );
}

This code fails with GCC 4.9. GCC 5.2 even crashes with a segfault. Clang 3.6
compiles it and gives the expected console output:

1
blub
3.141500
4
5.2

The curious thing is: When I remove the wrapping lambda, i.e. the line 

[&]
{
}();

then is compiles fine in all cases. Also when I replace decltype(args) with Ts,
then it compiles fine and produces the correct console output. Go figure!

[Bug libstdc++/60564] New: [C++11] The std::packaged_task constructor taking a reference to a functor does not copy its argument.

[ralph.tandetzky at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60564

Bug ID: 60564
   Summary: [C++11] The std::packaged_task constructor taking a
reference to a functor does not copy its argument.
   Product: gcc
   Version: 4.8.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: libstdc++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: ralph.tandetzky at gmail dot com

The following code compiles successfully:

~
#include future
#include iostream

using namespace std;

struct Test
{
Test()   { cout  constructed.  endl; }
Test( const Test  ) { cout  copied.   endl; }
Test( Test  )  { cout  moved.endl; }
void operator()() const {}
};

int main()
{
Test t;
packaged_taskvoid() pt1( t );
}
~

It produces the following output:

~
constructed.
moved.
~

However, the constructor of std::packaged_taskvoid() should copy it's
argument into its internally stored task object according to 30.6.9.1 of the
C++11 standard (I'm referring to N3485, actually). 

Settings: I've used the online-compiler of http://en.cppreference.com/ with the
compiler GCC 4.8 (C++11). GCC 4.7 (C++11) does not have the bug, but produces a
correct output copying the object passed into the constructor.