Date: Wed, 8 Mar 2000 15:03:27 -0600 From: Oscar Bonilla <obonilla@fisicc-ufm.edu> To: freebsd-hackers@freebsd.org Subject: inner workings of the C compiler Message-ID: <20000308150327.A77039@fisicc-ufm.edu>
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i'm working on the C library, and to make debuggin easy i've copied
/usr/src/lib/libc to another directory and only build libc.a.
i've also copied /usr/src/lib/csu/i386-elf to another directory and
have enabled debug symbols on both csu and libc.
to try things out i create a static binary and coerce it to use my
C library instead of the system's one.
this is how i compile my program:
cc -g -DYP -DFreeBSD -Wall -pedantic -ansi -c -I../../libc/include nss-test.c
cc -g -nostdlib -static -L../../libc -o nss-test nss-test.o \
../../csu/i386-elf/crt1.o ../../csu/i386-elf/crti.o -lc
now, the program runs fine, but at the very end gives me a bus error
and core dumps... i've tracked the bug to the following call in line 90
csu/i386-elf/crt1.c in function _start()
atexit(_fini);
at this point, in gdb
(gdb) print _fini
$1 = {<text variable, no debug info>} 0x80528e4
(gdb) step
atexit (fn=0x80528e4)
at /usr/home/obonilla/freebsd/nss/libc/../libc/stdlib/atexit.c:59
1: __progname = 0xbfbffa86 "nss-test"
(gdb) print fn
$2 = (void (*)()) 0
fn is the argument to atexit()
later, in fuction exit() it will try to dereference a null pointer due
to the above...
i'm puzzled by this behavior... am i missing something?
how is it possible that the value i'm seeing before the call to atexit()
(0x80528e4) gets to be null once inside atexit()?
thanks and regards,
-oscar
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