Re: Patch: install libgtkpeer.so and libjawt.so in versioned library directory

[Andrew Haley <aph at redhat dot com>]

Thomas Fitzsimmons writes:
 > Andrew Haley wrote:
 > > Thomas Fitzsimmons writes:
 > >  > 
 > >  > Andrew Haley wrote:
 > >  > > Thomas Fitzsimmons writes:
 > >  > > 
 > >  > >  > +
 > >  > >  > +  // Check if LD_LIBRARY_PATH is already prefixed with
 > >  > >  > +  // GCJ_VERSIONED_LIBDIR.  If not, export LD_LIBRARY_PATH prefixed
 > >  > >  > +  // with GCJ_VERSIONED_LIBDIR and re-spawn gij.
 > >  > >  > +  char *libpath = getenv (LTDL_SHLIBPATH_VAR);
 > >  > >  > +  char *newpath = _Jv_PrependVersionedLibdir (libpath);
 > >  > >  > +
 > >  > >  > +  if (! libpath || strcmp (libpath, newpath))
 > >  > >  > +    {
 > >  > >  > +      setenv (LTDL_SHLIBPATH_VAR, newpath, 1);
 > >  > >  > +      JvFree (newpath);
 > >  > >  > +
 > >  > >  > +      int error_code = execv (GIJ_EXECUTABLE, (char* const*) argv);
 > >  > > 
 > >  > > But, as discussed with Bryce, the version in svn is
 > >  > > 
 > >  > >      int error_code = execvp (argv[0], (char* const*) argv);
 > >  > > 
 > >  > > This can break java-1.4.2-gcj-compat.
 > >  > > 
 > >  > > /usr/bin/java prefixes the LD_LIBRARY_PATH with the gij install dir.
 > >  > > Then, /usr/bin/java does an execv of PREFIX/gij, but it leaves argv[0]
 > >  > > pointing to /usr/bin/java rather than PREFIX/gij.
 > >  > 
 > >  > Yes, /usr/bin/java must now be symlinked to gij, rather than being a binary 
 > >  > wrapper itself.  The idea of this patch was to merge the functionality from 
 > >  > java-gcj-compat's java.c into gij itself, so that we could get rid of java.c in 
 > >  > favour of a symlink.
 > > 
 > > Can we not have a version of this that works correctly with
 > > already-installed systems?
 > 
 > We could, but that would need GIJ_EXECUTABLE, which Bryce didn't
 > like.  FWIW, to avoid confusion, and problems like the one you've
 > encountered, I prefer hard-coding executables that I intend to
 > exec.  But doing so would compromise Bryce's vision of a
 > relocatable libgcj.

Maybe, but you simply cannot assume that argv[0] contains the path to
the current executable.  It's a fragile technique that runs the risk
of horrors like this one.  /proc/self/exe works on Linux.

Andrew.