On 12/11/19 12:59 PM, Daniel P. Berrangé wrote:
On Wed, Dec 11, 2019 at 12:52:20PM -0600, Eric Blake wrote:
On 12/11/19 12:45 PM, Daniel P. Berrangé wrote:
This avoids leaving a zero length or partially generated output
file on errors.
Signed-off-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
---
docs/Makefile.am | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/docs/Makefile.am b/docs/Makefile.am
index eb8de80b9c..9a1f7a6117 100644
--- a/docs/Makefile.am
+++ b/docs/Makefile.am
@@ -259,21 +259,21 @@ man8_MANS = $(manpages8_rst:%.rst=%.8)
grep -v '^\.\. contents::' < $< | \
sed -e 's|SYSCONFDIR|$(sysconfdir)|g' \
-e 's|RUNSTATEDIR|$(runstatedir)|g' | \
- $(RST2MAN) > $@
+ $(RST2MAN) > $@ || { rm $@ && exit 1; }
But still allows a truncated view of the file if another process accesses
the file while RST2MAN is still running. Even better is to generate output
to a temp file then atomically mv it into place, so that no concurrent
process can ever see an incomplete file.
Is that a problem that actually impacts negatively in real world for builds?
In various places in the make rules, we've either done the "|| rm" approach,
or the temp file and rename approach. Personally I find the recipes using
the "|| rm" approach are more maintainable/readable.
If you're trying to browse the docs and build at the same time, such as
checking if your tweak to a doc renders well, you could hit it; but
you're also right that it's not a show-stopper problem. Go with
whatever is easier to maintain if you don't care about the issue of
atomicity in the files (the rm to avoid a long-term corruption is more
important than the atomic mv to avoid a short-term corruption).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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