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

brainpower brainpower at mailbox.org
Wed Mar 4 22:40:04 UTC 2020

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

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


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