[Buildroot] [PATCH 4/5] support/download: only create final temp file when needed

[Yann E. MORIN <yann.morin.1998@free.fr>]

Arnout, All,

On 2014-07-07 18:08 +0200, Arnout Vandecappelle spake thusly:
> On 06/07/14 23:27, Yann E. MORIN wrote:
> > Create the temp file in the final location only when it is needed.
> > 
> > This avoids the nasty experience of seeing lots of temp files in
> > BR2_DL_DIR, that would linger around in case the downloads fails.
> 
>  It would also help to add a
> 
> trap "rm -f ${tmp_dl}" EXIT HUP INT QUIT TERM
> 
> which also removes the need of doing the rm at the end. Of course, that trap is
> still racy (interrupt between mktemp and trap).
> 
>  But with the two temporary variables, adding a trap becomes even more
> difficult. Unless that part is refactored into a separate helper script of
> course :-)

Yep, added to the list of TODO. ;-)

> > Add a comment on why we don;t clean-up after git.
> 
>  Typo in don;t

Yep, already fixed.

[--SNIP--]
> > diff --git a/support/download/git b/support/download/git
> > index b0031e5..d3fcdaf 100755
> > --- a/support/download/git
> > +++ b/support/download/git
> > @@ -19,8 +19,6 @@ basename="${3}"
> >  output="${4}"
> >  
> >  repodir="${basename}.tmp-git-checkout"
> 
>  (not related to this patch) It's actually not a checkout, it's a bare clone.

And it's being renamed in a later patch.

> > -tmp_tar="$( mktemp "${BUILD_DIR}/.XXXXXX" )"
> > -tmp_output="$( mktemp "${output}.XXXXXX" )"
> >  
> >  # Play tic-tac-toe with temp files
> >  # - first, we download to a trashable location (the build-dir)
> > @@ -33,6 +31,8 @@ cd "${BUILD_DIR}"
> >  # Remove leftovers from a previous failed run
> >  rm -rf "${repodir}"
> >  
> > +# Upon failure, git cleans behind itself, so no need to catch failures here.
> > +# The only case when git would not clean up, is if it gets killed with SIGKILL.
> 
>  I think the SIGKILL is reason enough to do the rm explicitly in the script. Of
> course, this is only valid if you use the trap, otherwise you never reach the rm

Well, SIGKILL is not catchable. That's the main selling point of SIGKILL.
;-)

> (due to 'set -e').

Well, 'set -e' only kicks in for the final 'mv', since all other
commands and conditions in an if statement.

Also, I'm not a big fan of traps, although I can be abusing them from
time to time.

But OK, I'll add this to the TODO...

Regards,
Yann E. MORIN.

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