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Re: superfluous test in AC_CHECK_HEADERS?


From: Frederik Fouvry
Subject: Re: superfluous test in AC_CHECK_HEADERS?
Date: Tue, 17 Aug 2004 15:14:13 +0200 (CEST)

| > 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 :-)

So, this setup provides more fine-grained information in case of
problems.  OK - I think got it.

Thanks!

Frederik




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