Re: about documentation of AC_CHECK_HEADERS

[Vincent Torri]

On Sat, 14 Mar 2009, Vincent Torri wrote:

> Hey,
>
> in the manual, one can read in 
> http://www.gnu.org/software/autoconf/manual/autoconf.html#Generic-Headers
>
> "For each given system header file header-file in the blank-separated 
> argument list that exists, define HAVE_header-file (in all capitals). If 
> action-if-found is given, it is additional shell code to execute when one of 
> the header files is found. You can give it a value of `break' to break out of 
> the loop on the first match. If action-if-not-found is given, it is executed 
> when one of the header files is not found."
>
> if I do that:
>
> AC_CHECK_HEADERS([foo.h bar.h], [have_headers="yes"], [have_headers="no"])
>
> So, 'action-if-found' and 'action-if-not-found' are given.
>
> Now, suppose that foo.h exists, but bar.h does not.
>
> According to the first part of the doc : "If action-if-found is given, it is 
> additional shell code to execute when one of the header files is found.", as 
> foo.h exists, have_headers="yes" is executed.
>
> But according to the second part: "If action-if-not-found is given, it is
> executed when one of the header files is not found", as bar.h does not exist, 
> have_headers="no" is executed...
>
> I don't know the real behavior of AC_CHECK_HEADERS, but clearly, there is a 
> problem with the documentation.
>
> Imho, the correct behavior woul be "if action-if-found is given, it is 
> additional shell code to execute when all the header files are found. If 
> action-if-not-found is given, it is executed when one of the header files is 
> not found"
>
> am I wrong ?

more precisely, if foo.h exists and bar.h does not:

1) with:

AC_CHECK_HEADERS([foo.h bar.h], [have_headers="yes"], [have_headers="no"])

have_headers value is "no"

2) with:

have_headers="no"
AC_CHECK_HEADERS([foo.h bar.h], [have_headers="yes"])

have_headers value is "yes"

which is quite annoying, in my humble opinion

> Vincent Torri
>
>
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