[pacman-dev] [PATCH 1/2] Add config option to specify amount of concurrent download streams

[Allan McRae]

On 5/3/20 8:40 am, brainpower wrote:
> Am 04.03.20 um 23:32 schrieb brainpower:
>> Hi!
>>
>> Am 04.03.20 um 22:29 schrieb Anatol Pomozov:
>>> On Wed, Mar 4, 2020 at 12:39 PM Anatol Pomozov <anatol.pomozov at gmail.com> wrote:
>>>> +               } else if(strcmp(key, "ConcurrentDownloadStreams") == 0) {
>>>> +                       /* TODO: what is the best way to handle int conversion errors? */
>>>> +                       config->concurrent_download_streams = atoi(value);
>>>
>>> Here is a question I have. What is the best way to handle int
>>> conversion errors for this option?
>>>
>>
>> I'd recommend strtol() [1] over atoi() any time.
>> It makes it a lot easier to get error handling right, well, in most cases actually possible at all!
>>
>> I do not know of any way to differentiate between a valid "0" input and the error case with atoi().
>> There is no way to detect if the input was out of range, atoi() just gives some undefined value.
>> (The only valid use case for atoi() I might find acceptable would be if you can be *absolutely* sure the input is a valid int. e.g. validate before passing to atoi)
>>
>>
>> With strtol() do the following:
>>
>> 1. Call strol()
>> 2. Check if *end is NULL, if it is not, parsing was aborted at the position *end points to
> 
> Sorry.
> I messed up and misread the documentation here. The first part of the above is incorrect.
> 
> You'll have to check str != end, where str is the first pointer passed to strtol and end the second.
> 
> 
>> 3. Check errno for ERANGE, it gets set if the integer given does not fit into a long
>> 4. Now use the number. Check range again, if you want to downcast the long to int.
>>
>> [1]: https://en.cppreference.com/w/c/string/byte/strtol
>>

man strtol has an example usage program, and provides instuctions on how
to check for "0" from input vs error.   For pacman, that would likely be
considered an error anyway.

A