Re:Re: G++ preprocessor problem with unary ## -- summary

[Fernando Rodriguez Salazar <fernando at elec dot gla dot ac dot uk>]

References: <3.0.6.32.20010319230315.007b5610@mail.cs.ubc.ca> 
<3.0.6.32.20010319230315.007b5610@mail.cs.ubc.ca> 
<20010320074333.D12047@daikokuya.demon.co.uk> 
<3.0.6.32.20010321090201.008456e0@mail.cs.ubc.ca>

>Dave Martindale wrote:- > After doing this, I noticed that the LEDA authors 
>must have known about
> the problem already, because the header file which #includes the troublesome
> file has a special check for DECCXX.  If that symbol is defined, the outer
> header file includes a pre-expanded version of the troublesome file rather
> than the "normal" one.  This says to me that they *knew* the code didn't
> work properly on at least one compiler, but rather than fixing it at the
> source level they built an ugly workaround instead. :-) Someone somewhere 
>said it has been fixed upstream; though I have no idea how. Neil.

If you are like me, you are intersted in getting things working as fast as 
possible (hey, this is part of my research!).  I contacted Algorithmics 
Solutions,  like it was suggested in this thread, and unfortunately their 
answer was "buy the new product, when we release the next version".  I'm 
sorry but I just can't wait anymore.  So here's a quick and dirty kloodge to 
get it working.  I am using GCC 3.0 on Solaris 2.7, with LEDA R 4.0.

To override the problem with the unary ##,  I only fooled the system to 
include the patch for the DECCXX.  That is, I changed LEDA/event.h to read 
something like:

//#if defined (__DECCXX)
#include <LEDA/event_nomacs.h>
//#else
//#include <LEDA/event_macros.h>
//#endif

simple and effective.  Once you've done this, you need to recompile the 
libraries, or else they will not link with your code.  To do this, a few 
changes are required in the Makefile (actually in  Makefile.src, in the 
LEDA/src directory).  First make sure g++ is the default compiler and linker. 
Next and very important make sure the code compiles with -fPIC, by having the 
line:

PIC = -fPIC

(note the capitals).  Now this is done, it is time to recompile the 
libraries; backup what you want, and then:

cd $LEDA
make del
make

It will compile for a while, and then it will stop with an error relating to 
iostream.  The opffending file is LEDA/stream.h. In that file, change the 
conflicting  lines which look something like:

cmd_ostream (char *cmd):ofstream(fileno(popen(cmd,"r")))

to


cmd_ostream (char *cmd):ofstream((const char *) fileno(popen(cmd,"r")))

In my case there were 4 such lines (2 for input stream and 2 for output).

return to the LEDA directory, and again tyupe make.  Now, if you are ins 
Solaris, another error will appear, complaining about one system header file 
with "ISO C++ forbids blah blah blah".  Just manually recompile that file 
appending the option -fpermisive.  You'll need to change into the proper 
directory first; I think it is LEDA/src/x11, but I am not completely 
possitive. 

Afer this is done, return to the LEDA directory, and finally issue the last 
Make.  It should compile the rest fine.

Now you can compile your code; just two words of warning:

1) Make sure you use g++ to link it.  I usually linked with gcc and that 
doesn't work anymore, since it doesnt include the c++ library.

2) One of my source files triggers and internal GCC error.  I have already 
reported the bug.  If such a thing happens to you, be sure to report the bug, 
and try compiling without oprimization.  That worked for me.


Good Luck!


Fernando Rodriguez-Salazar
ACS, University of Glasgow