[Bug libstdc++/94749] New: std::istream::ignore discards too many characters

[serpent7776 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94749

Bug ID: 94749
   Summary: std::istream::ignore discards too many characters
   Product: gcc
   Version: unknown
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: libstdc++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: serpent7776 at gmail dot com
  Target Milestone: ---

Created attachment 48369
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48369&action=edit
full source example

The following code results in '=' assigned to c when using libstdc++, but '+'
is assigned when using libc++, I believe libc++ is correct here

std::stringstream s(" +=");
char c;
s.ignore(1, '+');
s >> c;

Tested this on godbolt with newest gcc and locally on FreeBSD with gcc7
(command: g++7 -Wall -Wextra -pedantic test.cpp)

https://godbolt.org/z/yS5je8

[Bug libstdc++/94749] std::istream::ignore discards too many characters

[serpent7776 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94749

--- Comment #2 from serpent7776 at gmail dot com ---
any update?

[Bug libstdc++/94749] std::istream::ignore discards too many characters

[serpent7776 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94749

--- Comment #6 from serpent7776 at gmail dot com ---
thanks

[Bug c++/104470] New: internal compiler error: Segmentation fault compiling std::variant with -std=c++20

[serpent7776 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104470

Bug ID: 104470
   Summary: internal compiler error: Segmentation fault compiling
std::variant with -std=c++20
   Product: gcc
   Version: 10.3.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: serpent7776 at gmail dot com
  Target Milestone: ---

Created attachment 52396
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52396&action=edit
Preprocessed source

I encountered an internal compiler error while compiling the following code in
c++20 mode (no other flags are needed):

#include 

template 
struct Foo
{
T value;
};

template 
struct Bar
{
T value;
};

template 
using V = std::variant, Bar>;

int main()
{
V e = Foo("a");
}

When I switch to c++17 mode compiler does not crash.

I tested it on g++ 10.3.0 on FreeBSD 12.3-RELEASE-p1, but I can also reproduce
it on trunk version here https://godbolt.org/z/vn5Ws14Ma

Full error:

# g++10 -std=c++20 ice.ii
In file included from ice.cpp:1:
/usr/local/lib/gcc10/include/c++/variant: In substitution of 'template template using __accepted_type =
std::variant<_Types>::__to_type<__accepted_index<_Tp> > [with _Tp = _Tp&&;
 = typename std::enable_if, Bar
>::__not_self<_Tp&&>, void>::type; _Types = {Foo, Bar}]':
ice.cpp:20:15:   required from here
/usr/local/lib/gcc10/include/c++/variant:1335:36: internal compiler error:
Segmentation fault
 1335 |  using __accepted_type = __to_type<__accepted_index<_Tp>>;
  |^~~~
libbacktrace could not find executable to open

[Bug c++/56958] Spurious set but not used variable warning in empty pack expansion

[serpent7776 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56958

serpent7776 at gmail dot com changed:

   What|Removed |Added

 CC||serpent7776 at gmail dot com

--- Comment #7 from serpent7776 at gmail dot com ---
I was just hit by this warning in a very similar scenario.
To me this warning in this context is not only unhelpful, but confusing.
clang doesn't issue this warning in this context.

[Bug c++/101792] New: Compiling access to templated parent object fails with unrelated message: invalid use of 'auto'

[serpent7776 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101792

Bug ID: 101792
   Summary: Compiling access to templated parent object fails with
unrelated message: invalid use of 'auto'
   Product: gcc
   Version: unknown
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: serpent7776 at gmail dot com
  Target Milestone: ---

Sorry for the title, but I don't know how to describe the issue.

The following code fails to compile with error message:

: In instantiation of 'int fun(Ts ...) [with Ts = {int, int, int}]':
:26:10:   required from here
:21:41: error: invalid use of 'auto'
   21 | return pack.template Value<0, int>::value;
  |~^
Compiler returned: 1


The mentioned line doesn't have `auto`, so it's at best a misleading error
message. `auto` from error message refers to the `auto` on previous line.
Clang compiles the code without issue.

If I remove `template` keyword from offending line, gcc compiles the code
without issue.

gcc 11.2 x86_64
flags: -std=c++17 -Wall -Wextra -pedantic -O2


#include 

template 
struct Value
{
const T& value;
};

template 
struct Pack;

template 
struct Pack, Ts...> : Value...
{
};

template 
int fun(Ts... ts)
{
auto pack = Pack, Ts...> {{ts}...};
return pack.template Value<0, int>::value;
}

void f()
{
fun<>(1, 2, 3);
}


link to godbolt to see the issue:
https://godbolt.org/z/z7so93Wq8