LINE_MAX

[Alejandro Colomar]

Hi Eric!

I think I found a bug in POSIX.1-2017 (and probably, previous ones too,
but didn't check).

<https://pubs.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html>:
     {LINE_MAX}
           Unless  otherwise  noted, the maximum length, in bytes, of a
           utility’s input  line  (either  standard  input  or  another
           file),  when  the  utility  is  described as processing text
           files. The length includes room for the trailing <newline>.
           Minimum Acceptable Value: {_POSIX2_LINE_MAX}

It doesn't say anything about the trailing null byte for the buffer that
holds it, but I assume it doesn't include it, from the context.

However:
<https://pubs.opengroup.org/onlinepubs/009695399/functions/fgets.html>:
The following sections are informative.
EXAMPLES

    Reading Input

    The following example uses fgets() to read each line of input. {LINE_MAX}, which defines the maximum size of the input line, is defined in the <limits.h> header.

    #include <stdio.h>
    ...
    char line[LINE_MAX];
    ...
    while (fgets(line, LINE_MAX, fp) != NULL) {
    ...
    }
    ...


This example seems to contradict my understanding of what limits.h says.

So, either limits.h should be explicit that the trailing null byte is
also included in LINE_MAX, or the example is bogus and should be fixed.
I guess it's the latter, although I wish it was the former, so we can
avoid a +1 in the code.

In any case, could you please forward this to the Austin group?

Have a lovely night!
Alex

-- 
<https://www.alejandro-colomar.es/>
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