[PATCH] alpm: return -1 for error in find_dl_candidates

[Andrew Gregory]

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                                                                                                                                                                                [0][1016]
> >> 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.

apg