linking in a custom libc

[Federico David Sacerdoti]

I would like to link in a version of the glibc shared library with debugging
symbols in it. I have sucessfully compiled such a version of the library,
libc-2.2.2.so. But since the linker automatically links in the standard libc
without being told, I am having problems redirecting it to my freshly compiled
version.

Is there a config file that the linker reads to know what libraries to link in
by default? I have tried to explicitly link in -lc but that didn't seem to
work, and neither did messing with /etc/ld.so.conf in Linux.

I tried moving my new libc library with the debugging symbols into the master
location in /lib, but since I didn't want to loose my old one I renamed it
first. Bad idea. The mv command stopped working along with everything else and
the machine basically came to a halt. I didn't think to use rpm which is
statically linked to force a reinstall of the glibc pakage, but whatever,
I have a Tom's rescue disk.

Thanks
Dave

[Joe Durusau]

In general, name your lib something else,
tell gcc to link it in, and use something like -nostdlib
to tell gcc to bypass the standard lib(s). You don't
EVER want to mess with the std libc, as you now know.
Note: -nostdlib is from a vague memory, you might need to look
at the gcc docs, or if you want to go to a lot of trouble,
use gcc -v to see what it does, then use gcc -c to compile,
and ld to link. Just be prepared for a loe of heartburn.

A better solution might be to put an abort in your
prog somewhere, and use gdb to analyze the mess.

Speaking only for myself,

Joe Durusau

[Ken Whaley]

Here's a makefile with the magic required to do this. Someone
should add this to the glibc FAQ/HowTo, as the current ones do
not tell you everything you must do to get this to work. This
is for a shared build, if you want a static build I think all
you have to do is add -static to the link line, but I haven't
tested that.

testglibc = /usr/local/glibc2.2.3
gcc = gcc

.PHONY: all
all: hello

hello: hello.o
$(gcc) -Wl,--dynamic-linker=$(testglibc)/lib/ld-linux.so.2 \
-B$(testglibc)/lib/ \
-Wl,-rpath=$(testglibc)/lib \
$< -o $@

hello.o: hello.c
$(gcc) -c -g -O0 -I$(testglibc)/include $< -o $@

clean:
rm -f hello hello.o

"Joe Durusau" <dur...@bellsouth.net> wrote in message
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