Since July 1996, most work on Octave has been done using a
Linux/GNU system, and a number of people who regularly test Octave
snapshot releases also primarily use Linux/GNU systems.

However, I have recently started to receive a significant number of
reports from people who say that they can't compile or run Octave on
Linux/GNU systems.  In nearly every case, the problem has turned out
to be that the compilers or libraries have not been installed
properly.  I suspect that this often results from a botched upgrade,
or from attempting to install the compilers from the standard source
distributions.  But in some cases, the cause has been a buggy Linux
distribution.  Many of these problems go unnoticed because much of the
software for Linux is written in C, not C++.

Octave compiles, but it won't run
---------------------------------

If you can compile Octave, but it crashes with a segmentation fault
right away, you probably have incompatible versions of libc and libg++
installed, or you have a version of the dynamic loader, ld.so, that is
incompatible with your versions of the libraries, or both.

On my development system, I am using the following software:

  * Linux kernel 2.0.6
  * gcc/g++ 2.7.2
  * libg++/libstdc++ 2.7.1.0
  * libm 5.0.5
  * libc 5.2.18
  * libncurses 3.0
  * ld.so 1.7.14

I know from experience that the versions listed above seem to work
well together.  But if you have a newer version of the kernel, you may
need a newer version of the C library.  I don't have time to keep up
with all the various library versions (life is much too short for
that), nor do I know which combinations are supposed to work together.
That sort of information should be clearly stated in the release notes
for the libraries.  If it is not, please ask the maintainers of the
libraries to clarify the documentation.

Octave won't even compile
-------------------------

If you can't compile Octave, you should first check to see that your
compiler and header files are properly installed.  Do you have
multiple versions of the g++ include files on your system?  Are you
sure that your copy of g++ is finding the right set?  You can find out
by compiling a simple C++ program with -v:

bash$ cat foo.cc
#include <iostream.h>
int main (void} { cerr << "yo\n"; return 0; }

bash$ g++ -v foo.cc
gcc -v foo.cc -lg++ -lstdc++ -lm
Reading specs from /usr/lib/gcc-lib/i486-linux/2.7.2/specs
gcc version 2.7.2
 /usr/lib/gcc-lib/i486-linux/2.7.2/cpp -lang-c++ -v -undef ...
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/g++-include
 /usr/local/include
 /usr/i486-linux/include
 /usr/lib/gcc-lib/i486-linux/2.7.2/include
 /usr/include
End of search list.
...

If the location of the correct set of include files is not listed in
the search path, then you might be able to fix that with a symbolic
link.  However, if your version of libg++ was not compiled with your
current version of gcc, you are likely to run into more trouble.

Upgrading your compiler and libraries
-------------------------------------

Finally, installing libg++ on a Linux system is not as simple as it
should be, because libg++ shares some basic I/O code with the Linux C
library, and they must be compatible.  You should get and read the
release notes for the compiler and libraries.

John W. Eaton
jwe@bevo.che.wisc.edu
University of Wisconsin-Madison
Department of Chemical Engineering

Sat Dec 14 09:44:05 1996