PR 4286 causes segfault - please revert

[ja11sop]

Recent PR #4286 causes segfault.

The following code:

std::ostringstream Stream;
std::string Line = "";
Stream << fmt::format( "{}", fmt::styled( Line, fmt::fg( fmt::terminal_color::blue ) ) ) << "\n";

segfaults with backtrace:

#0  0x000055555568bbf3 in fmt::v11::detail::buffer<char>::append<char> (this=0x0, begin=begin@entry=0x7fffffffb400 "\033[34m", end=end@entry=0x7fffffffb405 "")
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/base.h:1797
#1  0x00005555556a69e3 in fmt::v11::detail::copy<char, char const*, fmt::v11::basic_appender<char>, 0> (begin=0x7fffffffb400 "\033[34m", end=0x7fffffffb405 "", out=...)
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/base.h:2008
#2  0x00005555556984d2 in fmt::v11::formatter<fmt::v11::detail::styled_arg<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, char, void>::format<fmt::v11::context> (
    this=0x7fffffffb480, arg=..., ctx=...) at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/color.h:574
#3  0x000055555568bcf1 in fmt::v11::detail::value<fmt::v11::context>::format_custom<fmt::v11::detail::styled_arg<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, fmt::v11::formatter<fmt::v11::detail::styled_arg<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, char, void> > (arg=0x7fffffffbaf0, parse_ctx=..., ctx=...)
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/base.h:2240
#4  0x000055555570f6af in fmt::v11::basic_format_arg<fmt::v11::context>::handle::format (this=<optimized out>, parse_ctx=..., ctx=...)
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/base.h:2444
#5  0x000055555570d9bd in fmt::v11::detail::default_arg_formatter<char>::operator() (this=0x7fffffffb608, h=...) at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/format.h:3488
#6  0x000055555570c767 in fmt::v11::basic_format_arg<fmt::v11::context>::visit<fmt::v11::detail::default_arg_formatter<char> > (this=this@entry=0x7fffffffb5c0, vis=...)
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/base.h:2484
#7  0x000055555570a4b3 in fmt::v11::detail::vformat_to (buf=..., fmt=..., args=..., loc=...) at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/format-inl.h:1454
#8  0x000055555570a387 in fmt::v11::vformat[abi:cxx11](fmt::v11::basic_string_view<char>, fmt::v11::basic_format_args<fmt::v11::context>) (fmt=..., args=...)
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/format-inl.h:1444
#9  0x000055555568269d in fmt::v11::format<fmt::v11::detail::styled_arg<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > (fmt=...)
    at /home/user/_download/git_https_github.com__fmtlib_fmt.git/include/fmt/format.h:4186

[phprus]

Please, test last release: https://github.com/fmtlib/fmt/releases/tag/11.1.1

PR #4286 does not change formatting using fmt::styled.

[ja11sop]

Latest release works fine - latest commits breaks this.

[ja11sop]

As a note - we build off head and we noticed this as tests all were passing until the related PR was merged to master, then everything broke. It was only after investigating and seeing this PR that it became apparent what had happened. We verified by rolling back to the latest release which then works as normal.

[phprus]

@ja11sop
Commit with new test:

phprus@7b5d994

All tests pass without errors:
https://github.com/phprus/fmt/actions/runs/12610957196
https://github.com/phprus/fmt/actions/runs/12610957193
https://github.com/phprus/fmt/actions/runs/12610957192

Please, test PR: #4290

[ja11sop]

As noted on the PR I cloned and ran against this PR and code worked as expected. PR is a nice simplification!