Re: [PATCH 4/8] libstdc++: Fix error handling in std::print

[Tim Song <t.canens.cpp@gmail.com>]

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[print.fun] requires a system_error, but I don't think
[ostream.formatted.print] does?

On Tue, Feb 27, 2024 at 5:47 AM Jonathan Wakely <jwakely@redhat.com> wrote:

> Tested x86_64-linux. Reviews invited.
>
> -- >8 --
>
> The standard requires an exception if std::print fails to write to a
> std::ostream.
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/ostream (vprint_nonunicode): Throw if stream state
>         indicates writing failed.
>         * testsuite/27_io/basic_ostream/print/1.cc: Check for exception.
>         * testsuite/27_io/print/1.cc: Likewise.
> ---
>  libstdc++-v3/include/std/ostream                |  5 +++++
>  .../testsuite/27_io/basic_ostream/print/1.cc    | 17 +++++++++++++++++
>  libstdc++-v3/testsuite/27_io/print/1.cc         | 16 ++++++++++++++++
>  3 files changed, 38 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/ostream
> b/libstdc++-v3/include/std/ostream
> index a136399ad0b..3740ad6edfa 100644
> --- a/libstdc++-v3/include/std/ostream
> +++ b/libstdc++-v3/include/std/ostream
> @@ -901,6 +901,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         __catch(...)
>           { __os._M_setstate(ios_base::badbit); }
>        }
> +
> +    if (!__os)
> +      __throw_system_error(EIO);
>    }
>
>    inline void
> @@ -974,6 +977,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         __catch(...)
>           { __os._M_setstate(ios_base::badbit); }
>        }
> +    if (!__os)
> +      __throw_system_error(EIO);
>  #endif // _WIN32
>    }
>
> diff --git a/libstdc++-v3/testsuite/27_io/basic_ostream/print/1.cc
> b/libstdc++-v3/testsuite/27_io/basic_ostream/print/1.cc
> index 71a4daa04c9..14bfb14d556 100644
> --- a/libstdc++-v3/testsuite/27_io/basic_ostream/print/1.cc
> +++ b/libstdc++-v3/testsuite/27_io/basic_ostream/print/1.cc
> @@ -103,6 +103,22 @@ test_locale()
>    }
>  }
>
> +void
> +test_errors()
> +{
> +#ifdef __cpp_exceptions
> +  std::stringstream in(std::ios::in);
> +  try
> +  {
> +    std::print(in, "{}", "nope");
> +    VERIFY(false);
> +  }
> +  catch (const std::system_error&)
> +  {
> +  }
> +#endif
> +}
> +
>  int main()
>  {
>    test_print_ostream();
> @@ -111,4 +127,5 @@ int main()
>    test_print_no_padding();
>    test_vprint_nonunicode();
>    test_locale();
> +  test_errors();
>  }
> diff --git a/libstdc++-v3/testsuite/27_io/print/1.cc
> b/libstdc++-v3/testsuite/27_io/print/1.cc
> index 6a294e0454b..d570f7938be 100644
> --- a/libstdc++-v3/testsuite/27_io/print/1.cc
> +++ b/libstdc++-v3/testsuite/27_io/print/1.cc
> @@ -74,6 +74,21 @@ test_vprint_nonunicode()
>    // { dg-output "garbage in . garbage out" }
>  }
>
> +void
> +test_errors()
> +{
> +#ifdef __cpp_exceptions
> +  try
> +  {
> +    std::print(stdin, "{}", "nope");
> +    VERIFY(false);
> +  }
> +  catch (const std::system_error&)
> +  {
> +  }
> +#endif
> +}
> +
>  int main()
>  {
>    test_print_default();
> @@ -82,4 +97,5 @@ int main()
>    test_println_file();
>    test_print_raw();
>    test_vprint_nonunicode();
> +  test_errors();
>  }
> --
> 2.43.0
>
>