I have seen several versions of this problem posted on the web. Since
the
answers were wrong I thought that I would correct them. This particular
version was posted by Perry Lee Anthony on Friday May 2, 1997 to the
redhat archive.
"I have a program that is made up of mostly "c" modules, a few fortran
modules, and a few c++ modules. I compile and run this program on many
different platforms (AIX, VAX openVMS, Digital Unix, SysV) and have
decided to try to compile it on linux. I have RedHat 4.1 and have
installed the g77 ver 0.19 that goes with gcc 2.7.2.1 (it replaced the
/usr/bin/gcc from the redhat dist with the one that works with g77). I
can compile and run fortran programs just fine with g77. Now I make a
library that contains fortran modules, c modules, and c++ modules. Then
I compile the main c-routine (the module with main()), linking to this
library and to the other needed libraries (including libg77). Linking
fails with "unresolved reference to MAIN__ in libg77". AARRG. I can't
figure out what to do about this, and I'm probably not giving enough
information for people to help, but any guesses would be appreciated.
Thanks, Perry"
In Perry's case as well as in the other case I saw the answer was the
same:
"link to -lf2c ". At least in my particular case this turned out to be
the problem, NOT the solution. My linker message was:
"unresolved reference to MAIN__ in /usr/lib/libf2c.so"
I did a name list on libf2c (nm /usr/lib/libf2c.so | grep MAIN__)
and got back that it was undefined (U MAIN__). Well, when you compile
pure fortran using f2c the compiler defines MAIN__ (try writing a hello
world program hello.f and then compile it with fort77 -c and then do nm
on
hello.o) . So the problem then is that libf2c expects to find
MAIN__ defined during the final link phase. In my makefile I added the
line:
.f.o:
$(FF) -c -O 2 $<
and REMOVED the final link to -lf2c and everything works fine now.
I still do not understand what happened during my upgrade that made
a working makefile stop working. It seems that under certain conditions
linking to -lf2c doesn't work and under other conditions it does. In any
case, I believe that the above is a reasonable fix to this problem. I
suspect
that similar fixes will work for g77 although I haven't tried.
Finally, if I am sending this to the wrong place, well, sorry about
that!
Side remark on a nonportable fix:
renaming main()
MAIN__()
and wrapping extern "C" { MAIN__(){main prog}
around main also fixed the problem but I don't recommend this!
--
John Pearson E-mail: [EMAIL PROTECTED]
XCM MS F645 Phone:(505)-667-7585
Los Alamos National Laboratory
Los Alamos, NM 87545
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