This commit broke support for using git with musl libc: https://github.com/git/git/commit/2f8952250a84313b74f96abb7b035874854cf202 Rather than depending on non-portable GNU regex extensions, there is a simple portable fix for the issue this code was added to work around: When a text file is being mmapped for use with string functions which depend on null termination, if the file size: 1. is nonzero mod page size, it just works; the remainder of the last page reads as zero bytes when mmapped. 2. if an exact multiple of the page size, then instead of directly mmapping the file, first mmap a mapping 1 byte (thus 1 page) larger with MAP_ANON, then use MAP_FIXED to map the file over top of all but the last page. Now the mmapped buffer can safely be used as a C string. If such a solution is acceptable I can try to prepare a patch. Rich