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Detect when a .do script deletes its stdout tmp file.

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This can happen if we create the .tmp file in the same directory as the
target, and the .do file first does "rm -rf" on that directory, then
re-creates it.  The result is that the stdout file is lost.

We'll make this a warning if the .do script *didn't* write to stdout
(so the loss is harmless, just weird), and an error if they *did* write
to stdout, which we can detect because we still have an open fd on the
file, so we can fstat() it.
This commit is contained in:
Avery Pennarun 2018-12-12 03:36:09 +00:00
commit 1f79bf1174
5 changed files with 43 additions and 3 deletions
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17
redo/builder.py
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@ -344,8 +344,17 @@ class _BuildJob(object):
before_t = self.before_t
after_t = _try_stat(t)
st1 = os.fstat(f.fileno())
st1b = _try_stat(self.tmpname1)
st2 = _try_stat(self.tmpname2)
if (after_t and
if not st1.st_size and not st1b:
warn("%s: %s deleted %s; don't do that.\n"
% (_nice(t), argv[2], self.tmpname1))
# not fatal, continue
if st1.st_size > 0 and not st1b:
err('%s: %s wrote to stdout but deleted %s.\n'
% (_nice(t), argv[2], self.tmpname1))
rv = 207
elif (after_t and
(not before_t or before_t.st_mtime != after_t.st_mtime) and
not stat.S_ISDIR(after_t.st_mode)):
err('%s modified %s directly!\n' % (argv[2], t))
@ -365,11 +374,15 @@ class _BuildJob(object):
except OSError, e:
dnt = os.path.dirname(t)
if not os.path.exists(dnt):
# This could happen, so report a simple error message
# that gives a hint for how to fix your .do script.
err('%s: target dir %r does not exist!\n' % (t, dnt))
else:
# I don't know why this would happen, so raise the
# full exception if it ever does.
err('%s: rename %s: %s\n' % (t, self.tmpname2, e))
raise
os.unlink(self.tmpname1)
unlink(self.tmpname1)
elif st1.st_size > 0:
try:
os.rename(self.tmpname1, t)