Re: autoconf: undocumented limitation

[Eric Blake]

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According to Bruno Haible on 4/6/2009 4:00 AM:
>> If the 
>> latter, then no, I don't think we should document that.  We should just
>> document that config.status works only on text files, i.e., the line
>> length is limited to LINE_MAX
> 
> Saying only "text files" would not be sufficient. The same long line
> in a .m4 file is supported without problems; these are also text files.

Ah, but autoconf requires GNU M4, which, as one of its many extensions to
POSIX, disregards LINE_MAX (in other words, the fact that you can use GNU
M4 to process a non-text file with long lines is a feature).  If we were
also portable to BSD m4 or Solaris m4, then our use of m4 would also be
affected by line length in non-text files.

> 
> Please say that the line length is limited. But what is LINE_MAX? If you
> mean LINE_MAX from <limits.h> [1], then such a statement is useless,
> because this value is platform dependent, and a reference to POSIX [2]
> does not help because HP-UX 11.00 and IRIX 6.5 are far away from POSIX
> compliance.

There are very few POSIX utilities which are required to disregard
LINE_MAX.  wc, sh, and tr come to mind.  But sed, awk, grep, and many
other common text manipulation tools are allowed to fall flat on their
face with long lines, just as they do with no trailing newline or embedded
NUL.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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