dependencies in .so files
Thu, 28 May 1998 11:34:56 +0100 (GMT+0100)
Martin Maechler writes:
> >>>>> "Guido" == Guido Masarotto <firstname.lastname@example.org> writes:
> >> From the dlopen man page:
> Guido> void *dlopen (const char *filename, int flag);
> Guido> ................................................
> Guido> RTLD_GLOBAL may be or'ed with flag
> Guido> in which case the external symbols defined in the library will be
> Guido> made available to subsequently loaded libraries.
> Guido> So, I try:
> Guido> 1) I modify src/unix/dynload.c changing the flag of dlopen
> Guido> from RTLD_LAZY to (RTLD_LAZY | RTLD_GLOBAL)
> Shall we do this, for 0.62? -- or even try to have "configure" find out
> if RTLD_GLOBAL is supported on the given system?
If I can give suggestions:
1) Independently from the RTLD_GLOBAL flag, I will change RTLD_LAZY to
RTLD_NOW. As Luke T. summarized yesterday in this way a shared library
which cannot resolve all its symbols (in R.binary or in other libraries)
cannot be load. This give three advantages:
a) At least under Linux, if I call a dynamic linked routine which
cannot resolve its dependencies, I get a segmentation fault and
R exit. Of course, we can try to intercept this problem but
as also Luke noted, it is difficult to be sure that all the systems
will trigs an appropriate signal; in addition
b) debugging of a shared library becomes simple; at least, we are
sure that all the functions in the library can be called.
c) This correspond to the standard for not Unix machine; I am
sure for Windows but, if I remember, Luke said also for the Mac.
Perhaps, if a library cannot be loaded, the corresponding dlerror()
string should be used for giving to the user some information
2) Coming to RTDL_GLOBAL; here the question is the one raised by
Luke: portability. I suppose that the solution suggested by
Luke (use "recursive" shared libraries) is more portable than mine.
After a first failure, I was able to run my "silly" example setting
the LD_LIBRARY_PATH shell variable,i.e., instructing ld.so about where
> Guido: Have you ever looked at 0.62 (and porting it to Win32) ?
> (get it from <CRAN>/src/devel/R-snapshot.tar.gz)
I had no time. I downloaded a snapshot next week but I didn't make
any trial. Is the unix/system.c changed a lot? I have just looked
to it now and it seems quite similar to the 0.61.x one.
To all the R people: have a nice day.
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