Re: superfluous test in AC_CHECK_HEADERS?

[Raja R Harinath]

Hi,

Frederik Fouvry <address@hidden> writes:

> I'm using 
>
> AC_CHECK_HEADERS([ecl.h])
>
> in configure.ac, and that gives the following in the log file
> (autoconf 2.57):
>
> configure:5067: checking ecl.h usability
> configure:5080: gcc -c -g -O2  -I/proj/contrib/lkb/latest/include 
> -I/proj/contrib/lib/ecl/h conftest.c >&5
> configure:5083: $? = 0
> configure:5086: test -s conftest.o
> configure:5089: $? = 0
> configure:5099: result: yes
> configure:5103: checking ecl.h presence
> configure:5114: gcc -E  -I/proj/contrib/lkb/latest/include 
> -I/proj/contrib/lib/ecl/h conftest.c
> configure:5120: $? = 0
> configure:5139: result: yes
> configure:5175: checking for ecl.h
> configure:5182: result: yes
>
> It first tests whether it can compile with the header file, and
> then tests if the file exists or not.  Is the second test not
> subsumed by the first one (if that one is successful)?

The first test uses $CFLAGS and $CPPFLAGS, while the second only uses
$CPPFLAGS.  If you have some -I and -D in your $CFLAGS, the results
will differ.

(I'm not justifying the double check.  I'm just saying that the second
is not entirely redundant :-)

- Hari
-- 
Raja R Harinath ------------------------------ address@hidden