https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108046
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:50bc490c090cc95175e6068ed7438788d7fd7040 commit r14-2825-g50bc490c090cc95175e6068ed7438788d7fd7040 Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Jul 27 14:07:09 2023 +0100 libstdc++: Fix std::format alternate form for floating-point [PR108046] A decimal point was being added to the end of the string for {:#.0} because the __expc character was not being set, for the _Pres_none presentation type, so __s.find(__expc) didn't the 'e' in "1e+01" and so we created "1e+01." by appending the radix char to the end. This can be fixed by ensuring that __expc='e' is set for the _Pres_none case. I realized we can also set __expc='P' and __expc='E' when needed, to save a call to std::toupper later. For the {:#.0g} format, __expc='e' was being set and so the 'e' was found in "1e+10" but then __z = __prec - __sigfigs would wraparound to SIZE_MAX. That meant we would decide not to add a radix char because the number of extra characters to insert would be 1+SIZE_MAX i.e. zero. This can be fixed by using __z == 0 when __prec == 0. libstdc++-v3/ChangeLog: PR libstdc++/108046 * include/std/format (__formatter_fp::format): Ensure __expc is always set for all presentation types. Set __z correctly for zero precision. * testsuite/std/format/functions/format.cc: Check problem cases.
