Re: how serious are these compiler warnings?

Segmentation fault in glink.fflush at 0xd1fda988 ($t1)

Oh joy. ;)

that was pretty much my reaction :)

There's some odd bletcherousness in the AIX linker and dynamic loader,
bordering on true evil.  The basic problem is that if you do the following:

1) Link -lbar -lbaz     where and are also shared libs.

2) then link main program    cc -o main main.c -lfoo  *and omit -lbar -lbaz*

It's possible for it to link successfully at compile time, but at runtime,
what happens is:

a) main gets loaded.
b) gets loaded, and calls from main to are relocated.
c) calls from to and are *not* relocated.
d) You take a wild branch out of trying to call bar or baz.

So, by default, AIX is rather like Windows or OpenVMS in that the library an executable loads cannot reach-out and call a routines from the executable itself :(

The run-time symptom is a segfault in glink.* (usually, trying to load a
wild address pointer for the un-relocated function....)

To fix, you need to do one of:

a) Add '-brtl' flags at appropriate places (you may need to rebuild all the
libraries involved).  The rtl is "run-time-linker" and basically does relocation
and call resolution on after it gets loaded.

Am I correct in assuming that also means main?

b) Making the final main program link look like:

cc -o mail -lfoo -lbar -lbaz

(making sure that *all* the needed shared libs are listed) - this way, and will be loaded and relocated at startup along with

Option (b) is usually easiest.

I think I need to take option a - in my case libfoo is being dynamically loaded vi g_module_open.

I would have thought that libtool would have included that option for AIX when it was told to -export-dynamic?

Anyway, I'll try adding the -brtl and see what happens.  Thanks,

rick jones

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]