https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110574
--- Comment #6 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:2f6bbc9a7d9a62423c576e13dc46323fe16ba5aa commit r14-2476-g2f6bbc9a7d9a62423c576e13dc46323fe16ba5aa Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Jul 6 17:10:41 2023 +0100 libstdc++: Fix --enable-cstdio=stdio_pure [PR110574] When configured with --enable-cstdio=stdio_pure we need to consistently use fseek and not mix seeks on the file descriptor with reads and writes on the FILE stream. There are also a number of bugs related to error handling and return values, because fread and fwrite return 0 on error, not -1, and fseek returns 0 on success, not the file offset. libstdc++-v3/ChangeLog: PR libstdc++/110574 * acinclude.m4 (GLIBCXX_CHECK_LFS): Check for fseeko and ftello and define _GLIBCXX_USE_FSEEKO_FTELLO. * config.h.in: Regenerate. * configure: Regenerate. * config/io/basic_file_stdio.cc (xwrite) [_GLIBCXX_USE_STDIO_PURE]: Check for fwrite error correctly. (__basic_file<char>::xsgetn) [_GLIBCXX_USE_STDIO_PURE]: Check for fread error correctly. (get_file_offset): New function. (__basic_file<char>::seekoff) [_GLIBCXX_USE_STDIO_PURE]: Use fseeko if available. Use get_file_offset instead of return value of fseek. (__basic_file<char>::showmanyc): Use get_file_offset.
