do-lookup.h regarding to mips/dlsym and libstdc++

[Yoriko Komatsuzaki <yoriko at sm dot sony dot co dot jp>]

Sorry, please destroy my last mail because of miss.

Regarding to my last mips dlsym question, I investigated a little more.
And I think that such an attached process should be required. 

(I don't know that this is enough.)

Because even though UNDEF symbol is found, 
it can process as global symbol for the rare occasion.

This phenomena is showed only in mips. When libstdc++ is linked in
proior libc, the malloc's entry in libstdc++ MIPS.stubs table seemed to
be recognized as the malloc global symbol ...

How do you feel about it?

--- glibc-2.5/elf/do-lookup.h.org        2006-09-05 05:40:11.000000000 +0900
+++ glibc-2.5/elf/do-lookup.h   2008-01-29 11:17:40.000000000 +0900
@@ -222,7 +222,7 @@ do_lookup_x (const char *undef_name, uin
         no possible ambiguities.  */
       sym = num_versions == 1 ? versioned_sym : NULL;

-      if (sym != NULL)
+      if ((symidx != SHN_UNDEF) && (sym != NULL))
        {
        found_it:
          switch (ELFW(ST_BIND) (sym->st_info))



# g++ -fPIC -c -g dlsymtest.cc -o dlsymtest.o
# g++ -ldl -g -shared -o dlsymtest.so dlsymtest.o

############### case 0: without -lstdc++ --- OK
# gcc -g test.c -o test.0
# readelf -a test.0 | less
...
Dynamic section at offset 0x180 contains 25 entries:
  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]
 0x0000000c (INIT)                       0x40044c
 0x0000000d (FINI)                       0x4007f0
...
# export LD_PRELOAD=./dlsymtest.so
# ./test.0
# (OK)


############### case 1: -lc -lstdc++  --- OK
# gcc -g -lc -lstdc++ test.c -o test.1
# readelf -a test.1 | less
...
Dynamic section at offset 0x180 contains 26 entries:
  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]
 0x00000001 (NEEDED)                     Shared library: [libstdc++.so.6]
 0x0000000c (INIT)                       0x400464
 0x0000000d (FINI)                       0x400800
...
# export LD_PRELOAD=./dlsymtest.so
# ./test.1
# (OK)


############### case 2: -lstdc++ -lc  --- SEGV
# gcc -g -lstdc++ -lc test.c -o test.2
# readelf -a test.2 | less
...
Dynamic section at offset 0x180 contains 26 entries:
  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libstdc++.so.6]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]
 0x0000000c (INIT)                       0x400464
 0x0000000d (FINI)                       0x400800
...
# export LD_PRELOAD=./dlsymtest.so
# ./test.2
Segmentation fault


Thank you.
Yoriko Komatsuzaki

Attachment: test.c
Description: Binary data

Attachment: dlsymtest.cc
Description: Binary data