On Fri, Jul 18, 2014 at 6:03 AM, Karsten Blees <karsten.bl...@gmail.com> wrote: > Am 17.07.2014 19:05, schrieb René Scharfe: >> Am 17.07.2014 14:45, schrieb Nguyễn Thái Ngọc Duy: > [...] >> "These routines have traditionally been used by programs to save the >> name of a working directory for the purpose of returning to it. A much >> faster and less error-prone method of accomplishing this is to open the >> current directory (.) and use the fchdir(2) function to return." >> > > fchdir() is part of the POSIX-XSI extension, as is realpath(). So why not > use realpath() directly (which would also be thread-safe)?
But realpath still needs a given buffer (of PATH_MAX at least again). Unless you pass a NULL pointer as "resolved_name", then Linux can allocate the buffer but that's implementation specific . I guess we can make a wrapper "git_getcwd" that returns a new buffer. The default implementation returns one of PATH_MAX chars, certain platforms like Linux can use realpath (or something else) to return a longer path?  http://pubs.opengroup.org/onlinepubs/009695399/functions/realpath.html > For non-XSI-compliant platforms, we could keep the current implementation. > Or re-implement a thread-safe version, e.g. applying resolve_symlink() from > lockfile.c to all path components. > > > If I may bother you with the Windows point of view: > > There is no fchdir(), and I'm pretty sure open(".") won't work either. > > fchdir() could be emulated using GetFileInformationByHandleEx(FileNameInfo). > realpath() is pretty much what GetFinalPathNameByHandle() does. However, > both of these APIs require Windows Vista. > > Opening a handle to a directory can be done using FILE_FLAG_BACKUP_SEMANTICS, > which AFAICT MSVCRT.dll's open() implementation does _not_ do (could be > emulated in our mingw_open() wrapper, though). > > ...lots of work for little benefit, I would think. > We could wrap this "get cwd, cd back" pattern as well. So "save_cwd" returns an opaque pointer, "go_back" takes the pointer, (f)chdir back and free the pointer if needed. On platforms that support fchdir, it can be used, else we fall back to chdir. I think there are only four places that follow this pattern, here, setup.c (.git discovery), git.c (restore_env) and unix-socket.c. Enough call sites to make it worth the effort? -- Duy -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html