[PATCH] alpm: return -1 for error in find_dl_candidates
andrew.gregory.8 at gmail.com
Wed Oct 6 18:02:19 UTC 2021
On 10/05/21 at 06:53pm, Morgan Adamiec wrote:
> On 05/10/2021 18:49, Morgan Adamiec wrote:
> > On 05/10/2021 18:10, Andrew Gregory wrote:
> >> On 10/05/21 at 12:53pm, Morgan Adamiec wrote:
> >>> On 4 Oct 2021 8:28 pm, Andrew Gregory <andrew.gregory.8 at gmail.com> wrote:
> >>> On 10/04/21 at 08:09pm, morganamilo wrote:
> >>> > This is the error value generally used and the calling function
> >>> > explicitly checks for -1, later causing the error to be missed
> >>> > and the transaction to continue.
> >>> This result is not compared to -1, the result of download_files is. If
> >>> we want
> >>> to guarantee that download_files will return -1 on error, that's where
> >>> the
> >>> return should be normalized, not in find_dl_candidates. Tying the API
> >>> of one
> >>> function to another like this is just going to cause confusion and
> >>> breakage
> >>> when somebody forgets in the future. Really, the caller of
> >>> download_files
> >>> should just check for a successful return; we return 1 as an error from
> >>> lots of
> >>> functions.
> >>> I'll change that too. This should still be accepted though.
> >> Why? If your reasoning is just that -1 is a better error value, we use 1 in
> >> lots of other places like I said and I don't want to change that one at a time.
> >> $ grep 'return 1;' lib/libalpm/*.c src/*/*.c | wc -l 
> >> 132
> > Everywhere in the function returns -1. Lets at least be consistent for
> > the same function.
> Not to mention download_files returns 1 on everything up to date so 1 is
> not an error in this case.
find_dl_candidates, the function you are modifying, only return 0 or 1. The
problem is in download_files because it does not guarantee its own return
value: it's not returning 0 on success/-1 on error, it's returning <whatever
the functions it calls return>. Somebody modifying those functions in the
future will have a hard time understanding the significance of their return
values because they have to check not just the function calling them
(download_files), but also the function calling download_files. That's a good
recipe for confusion and exactly this kind of bug in the future. However you
want to fix this, it should be clear from looking at download_files what the
significance of find_dl_candidates' return value is.
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