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Re: fatal: Could not get current working directory: Permission denied | affected 2.10,2.11,2.12, but not 1.9.5 |

Am 17.03.2017 um 20:45 schrieb Stefan Beller:
On Fri, Mar 17, 2017 at 12:34 PM, René Scharfe <l.s.r@xxxxxx> wrote:
Am 15.03.2017 um 22:30 schrieb René Scharfe:
Am 15.03.2017 um 10:44 schrieb Zenobiusz Kunegunda:
$ git bisect bad
7333ed1788b4f2b162a35003044d77a716732a1f is the first bad commit
commit 7333ed1788b4f2b162a35003044d77a716732a1f
Author: René Scharfe <l.s.r@xxxxxx>
Date:   Mon Jul 28 20:26:40 2014 +0200

    setup: convert setup_git_directory_gently_1 et al. to strbuf

That's what I half-suspected, and I think by now I got an idea.  Here's
a test program:

And here's a patch for letting strbuf_getcwd() use the same getcwd(3)
extension that pwd(1) uses.  It avoids the need to guess the path's
length and thus reduces the chance of stumbling over strange error
codes.  I wonder if it helps in your case.


 strbuf.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/strbuf.c b/strbuf.c
index ace58e7367..4c02801edd 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -442,6 +442,14 @@ int strbuf_getcwd(struct strbuf *sb)
        size_t oldalloc = sb->alloc;
        size_t guessed_len = 128;
+       char *cwd;
+       cwd = getcwd(NULL, 0);

from my local man pages:

  As  an extension to the POSIX.1-2001 standard, Linux (libc4, libc5,
glibc) getcwd()
  allocates the buffer dynamically using malloc(3) if buf is NULL.  In
this case, the
  allocated buffer has the length size unless size is zero, when buf
is allocated as big
  as necessary.  The caller should free(3) the returned buffer.

This sounds specific to Linux (though I am reading Linux man pages,
which claim this; Also it seems I might have misread it as it also states
"The pathname is returned as the function result and via the
argument buf, if present.").

I'm only interested in FreeBSD for now, as that's the platform Zenobiusz reported the issue on and I haven't been able to reproduce it, so this is still a bit exploratory, but hopefully getting closer. This extension is used in the first version of pwd(1) in FreeBSD's repo, comitted 1994-05-26, so it was supported there basically forever.

The oldest version I found that's using the extention is NetBSD's pwd(1), which was committed 1993-03-21 and carries a SCCS timestamp of 1991-02-20. Visual Studio .NET 2003 supports it as well.

Looking further:

  These functions are often used to save the location of the current
  working directory for the purpose of returning to it later.  Opening the
  current directory (".")  and  calling  fchdir(2)  to return is
usually a faster
  and more reliable alternative when sufficiently many file descriptors are
  available, especially on platforms other than Linux.

Not sure if that opens another door here?

Reducing the use of absolute paths may be a good idea in general, but that would probably require major changes. And Windows doesn't seem to offer fchdir() at all; I don't know if it has an equivalent function that could be used to build a replacement.