Symbol weirdness with static linking

[Jeremie Le Hen]

Hi hackers,

I created a library (libssp) which is to be linked in the same time as
libgcc (GCC's LIBGCC_SPEC [1]).  This library is intended to provide the
required symbols for ProPolice/SSP (Stack-Smashing Protector) which GCC
references whenever it has to protect a function.

This works almost perfectly but in one edge case : some programs
are so "simple" (IOW have no stack-based buffer) that GCC does not
feel the need to put any reference to the above symbols.  For instance,
bin/echo and bin/mkdir are such programs.

When libssp is linked dynamically, this is not a problem.  However, if
I use NO_DYNAMICROOT when building world, ld(1) complains that it does not
find the "syslog" symbol [2].  It happens that libssp uses syslog(3), but
since libssp won't be in the resulting executable, I don't understand
why ld(1) complains.

OTOH, programs which do have a reference to ProPolice symbols compile
without any problem.

Even weirder, while there are other calls to libc functions in libssp
- such as open(2), sigfillset(3) or sigprocmask(2) - if I comment out
the call to syslog(3), ld(1) does not complain any longer.  What is
so special with libc's "syslog" symbol ?  I don't understand what is
the difference here between, the "syslog" symbol and, say, the "sigfilset"
symbol (which is not used in echo(1) either).

For the sake of completeness, I added the output of some objdump(1)
outputs here :

/usr/obj/usr/src/bin/echo/echo.o:
http://tataz.chchile.org/~tataz/symbol_weirdness/objdump-t_echo.txt.gz

/usr/obj/usr/src/tmp/usr/lib/libc.a:
http://tataz.chchile.org/~tataz/symbol_weirdness/objdump-t_libc.txt.gz

/usr/obj/usr/src/tmp/usr/lib/libssp.a:
http://tataz.chchile.org/~tataz/symbol_weirdness/objdump-t_libssp.txt.gz


Thank you.
Regards,


[1]
#define LIBGCC_SPEC "%{shared: -lgcc_pic -lssp_pic} %{!shared: %{!pg: -lgcc -lssp} %{pg: -lgcc_p -lssp_p}}"


[2]
===> bin/echo (all)
cc -O2 -fno-strict-aliasing -pipe -march=pentium-m -fstack-protector -Wsystem-headers -Werror -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wcast-align -Wunused-parameter -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls -c /usr/src/bin/echo/echo.c
cc -O2 -fno-strict-aliasing -pipe -march=pentium-m -fstack-protector -Wsystem-headers -Werror -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wcast-align -Wunused-parameter -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls  -v -static -o echo echo.o
Using built-in specs.
Configured with: FreeBSD/i386 system compiler
Thread model: posix
gcc version 3.4.4 [FreeBSD] 20050518
 /usr/obj/usr/src/tmp/usr/bin/ld -V -Bstatic -o echo /usr/obj/usr/src/tmp/usr/lib/crt1.o /usr/obj/usr/src/tmp/usr/lib/crti.o /usr/obj/usr/src/tmp/usr/lib/crtbegin.o -L/usr/obj/usr/src/tmp/usr/lib echo.o -lgcc -lssp -lc -lgcc -lssp /usr/obj/usr/src/tmp/usr/lib/crtend.o /usr/obj/usr/src/tmp/usr/lib/crtn.o
GNU ld version 2.15 [FreeBSD] 2004-05-23
  Supported emulations:
   elf_i386_fbsd
/usr/obj/usr/src/tmp/usr/lib/libssp.a(ssp.o)(.text+0xe8): In function `__stack_smash_handler':
: undefined reference to `syslog'
*** Error code 1

-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >