This is normal, but you're not reading it right. Typically, a program 
conftest.c is generated on the fly and contains something like a #include of 
something you may or may not have. The first part of the program is labeled /* 
conftest.h */ which indicates that it is taken from that file of standard 
definitions. 

The contents of confdefs.h is actually mostly irrelevant (though I suppose 
there are cases when it isn't), the interesting bit is usually the line(s) that 
comes from elsewhere, e.g.

....
| #define HAVE_UNISTD_H 1
| #define HAVE_UTIME_H 1
| #define HAVE_ARPA_INET_H 1
| /* end confdefs.h.  */
| #include <dl.h>
configure:23459: result: no
configure:23459: checking for dl.h
configure:23459: result: no

This whole thint is about whether or not your system contains dl.h. When the 
compile fails, configure concludes that it doesn't. 

You only get to see the programs when they fail, but the same mechanism is 
behind all the other tests, like

configure:23459: checking langinfo.h presence
configure:23459: gcc -arch x86_64 -E -I/usr/local/include conftest.c
configure:23459: $? = 0
configure:23459: result: yes
configure:23459: checking for langinfo.h
configure:23459: result: yes

In some other cases, there is a rudimentary main() function, usually to check 
existence of specific library routines, and in a few cases there is a check 
whether the compiled program  actually runs.


-pd

> On 19 Nov 2017, at 02:02 , Rolf Turner <r.tur...@auckland.ac.nz> wrote:
> 
> P.S.  On a whim, I scanned through config.log some more and found many, many 
> errors logged and many, many "compilation terminated" notes.  In particular 
> there seem to be problems with a file "confdef.h", which repeatedly seems to 
> give rise to "fatal errors".  (Where is confdef.h?
> It seems to be nowhere.)

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd....@cbs.dk  Priv: pda...@gmail.com

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