The problem we are trying to deal with here is that some systems use a
function named stat and others, _stat. At the same time, the second arg
may be either (struct stat *) or (struct _stat *), and there's no apparent
correlation between the choice of the function and structure name. So we
have to figure out a combination that works. This was done by separately
choosing a valid function name and a valid structure name.
Confusing the issue is that we need the right answer in C++. The standard
configure macro that looks to see if a function foois available tries to
compile and link a little program:
char *foo();
main() { foo(); }
On our SGI (and your's, I expect), when this is done in C, both foo=stat
and foo=_stat work. Unfortunately, only one works in C++, so we have to
test for it in C++. Unfortunately, this test doesn't compile and link in
C++ with either stat or _stat, because the args aren't given. And we don't
know the right args. So the recent fix uses a double loop to figure out a
working combination: essentially
for f in stat _stat ; do
for s in stat _stat ; do
cat > tt.c << EOF
#include <sys/stat.h>
main() { int i = $f("foo", (struct $s *)0); }
EOF
if (eval "CC tt.c") > /dev/null 2>&1 ; then
fcn=$f
str=$s
fi
done
done
echo the function is $fcn
echo the structure name is $str
On our SGI this tells us the correct choice is stat in both cases -
function and structure name.
The fix we put in to acinclude.m4 works on several machines around here,
including our SGE (though the original code worked there, so I don't know
how much this tells us). If this script fails on your machine, then we
need to know why so we can fix it the new DX_CHECK_STAT autoconf macro. If
this script works on your system, then I guess we need to figure out why,
too - the actual macro includes additional logic to support other possible
include files etc.
Greg
Richard Gillilan <[EMAIL PROTECTED]>@opendx.watson.ibm.com on
06/21/2000 08:46:24 AM
Please respond to [email protected]
Sent by: [EMAIL PROTECTED]
To: [email protected]
cc:
Subject: Re: [opendx-dev] dx acinclude.m4
This patch may have just broken my configure (even more).
Configure now dies with a "could not find working combination of stat
function and
strcuture"
Perhaps it's a clue to what's wrong on my system.
[EMAIL PROTECTED] wrote:
> Update of /src/master/dx
> In directory opendx.watson.ibm.com:/tmp/cvs-serv12278
>
> Modified Files:
> acinclude.m4
> Log Message:
> AC_CHECK_FUNCS pathologically calls funcs with default "int func(void)"
> which doesn't work if the testing compiler is c++ and the function
prototype
> doesn't fortuitously match the default. Change to use AC_TRY_LINK
instead,
> to determine the working combination of stat function and structure
definitions.
