This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH v2] libstdc++: Add hexfloat/defaultfloat io manipulators.
- From: Jonathan Wakely <jwakely dot gcc at gmail dot com>
- To: Luke Allardyce <lukeallardyce at gmail dot com>
- Cc: Jonathan Wakely <jwakely at redhat dot com>, RÃdiger Sonderfeld <ruediger at c-plusplus dot de>, "libstdc++" <libstdc++ at gcc dot gnu dot org>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 15 Apr 2014 11:13:58 +0100
- Subject: Re: [PATCH v2] libstdc++: Add hexfloat/defaultfloat io manipulators.
- Authentication-results: sourceware.org; auth=none
- References: <20140327133723 dot GA13599 at redhat dot com> <1901588 dot qodTErPe42 at descartes> <20140327162714 dot GA13192 at redhat dot com> <CAFW6PZC0u5=i-KqQZZsbkmg5iWr6u2WVnnBQVqG8V2Bt6oOzOg at mail dot gmail dot com>
On 27 March 2014 23:56, Luke Allardyce wrote:
> It looks like the new standard also requires the precision to be
> ignored for hexfloat
>
>>For conversion from a floating-point type, if floatfield != (ios_base::fixed | ios_base:: scientific), str.precision() is specified as precision in the conversion specification. Otherwise, no precision is specified.
Thanks for pointing out that difference. We'll need a test for that.
> Also the old standard seems to require that ios_base::fixed |
> ios_base::scientific (or any other combination) falls through to the
> uppercase test; I was trying to use abi_tag for a solution as not only
> would two versions of _S_format_float be necessary, but also num_get
> due to the pre-instantiated templates for <char> and <wchar>, which
> led me to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60642. It might
> just be more trouble than it's worth.
I don't think we need to worry about that, if I understand correctly
the combination of fixed|scientific has unspecified behaviour in
C++03, so we can make our implementation do exactly what it does in
C++11.