Mercurial > hg
view tests/test-walkrepo.py @ 42562:97ada9b8d51b stable 5.0.2
posix: always seek to EOF when opening a file in append mode
Python 3 already does this, so skip it there.
Consider the program:
#include <stdio.h>
int main() {
FILE *f = fopen("narf", "w");
fprintf(f, "narf\n");
fclose(f);
f = fopen("narf", "a");
printf("%ld\n", ftell(f));
fprintf(f, "troz\n");
printf("%ld\n", ftell(f));
return 0;
}
on macOS, FreeBSD, and Linux with glibc, this program prints
5
10
but on musl libc (Alpine Linux and probably others) this prints
0
10
By my reading of
https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html
this is technically correct, specifically:
> Opening a file with append mode (a as the first character in the
> mode argument) shall cause all subsequent writes to the file to be
> forced to the then current end-of-file, regardless of intervening
> calls to fseek().
in other words, the file position doesn't really matter in append-mode
files, and we can't depend on it being at all meaningful unless we
perform a seek() before tell() after open(..., 'a'). Experimentally
after a .write() we can do a .tell() and it'll always be reasonable,
but I'm unclear from reading the specification if that's a smart thing
to rely on. This matches what we do on Windows and what Python 3 does
for free, so let's just be consistent. Thanks to Yuya for the idea.
author | Augie Fackler <augie@google.com> |
---|---|
date | Mon, 08 Jul 2019 13:12:20 -0400 |
parents | fa2423acb02f |
children | 2372284d9457 |
line wrap: on
line source
from __future__ import absolute_import, print_function import os from mercurial import ( hg, scmutil, ui as uimod, util, ) chdir = os.chdir mkdir = os.mkdir pjoin = os.path.join walkrepos = scmutil.walkrepos checklink = util.checklink u = uimod.ui.load() sym = checklink(b'.') hg.repository(u, b'top1', create=1) mkdir(b'subdir') chdir(b'subdir') hg.repository(u, b'sub1', create=1) mkdir(b'subsubdir') chdir(b'subsubdir') hg.repository(u, b'subsub1', create=1) chdir(os.path.pardir) if sym: os.symlink(os.path.pardir, b'circle') os.symlink(pjoin(b'subsubdir', b'subsub1'), b'subsub1') def runtest(): reposet = frozenset(walkrepos(b'.', followsym=True)) if sym and (len(reposet) != 3): print("reposet = %r" % (reposet,)) print(("Found %d repositories when I should have found 3" % (len(reposet),))) if (not sym) and (len(reposet) != 2): print("reposet = %r" % (reposet,)) print(("Found %d repositories when I should have found 2" % (len(reposet),))) sub1set = frozenset((pjoin(b'.', b'sub1'), pjoin(b'.', b'circle', b'subdir', b'sub1'))) if len(sub1set & reposet) != 1: print("sub1set = %r" % (sub1set,)) print("reposet = %r" % (reposet,)) print("sub1set and reposet should have exactly one path in common.") sub2set = frozenset((pjoin(b'.', b'subsub1'), pjoin(b'.', b'subsubdir', b'subsub1'))) if len(sub2set & reposet) != 1: print("sub2set = %r" % (sub2set,)) print("reposet = %r" % (reposet,)) print("sub2set and reposet should have exactly one path in common.") sub3 = pjoin(b'.', b'circle', b'top1') if sym and sub3 not in reposet: print("reposet = %r" % (reposet,)) print("Symbolic links are supported and %s is not in reposet" % (sub3,)) runtest() if sym: # Simulate not having symlinks. del os.path.samestat sym = False runtest()