when using g++, -export-symbols does not work as expected.

$ cat test.c
extern "C"
void _test()
{
        return;
}
extern "C"
void test()
{
        return;
}
$

-- created sample file.

$ libtool --tag=CXX --mode=compile g++ -c test.c -o test.lo
 g++ -c test.c  -fPIC -DPIC -o .libs/test.o
 g++ -c test.c -o test.o >/dev/null 2>&1
$

-- complited sample file.

$ libtool --mode=link gcc -o libtest.la -rpath /usr/lib -version-info 0:0:0
-export-symbols-regex '^test' test.lo
rm -fr  .libs/libtest.a .libs/libtest.exp .libs/libtest.la .libs/libtest.lai
.libs/libtest.so .libs/libtest.so.0 .libs/libtest.so.0.0.0 .libs/libtest.ver
generating symbol list for `libtest.la'
/usr/bin/nm -B  .libs/test.o  | sed -n -e 's/^.*[      
]\([ABCDGIRSTW][ABCDGIRSTW]*\)[         ][      ]*\([_A-Za-z][_A-Za-z0-9]*\)$/\1
\2 \2/p' | /bin/sed 's/.* //' | sort | uniq > .libs/libtest.exp
grep -E -e "^test" ".libs/libtest.exp" > ".libs/libtest.expT"
mv -f ".libs/libtest.expT" ".libs/libtest.exp"
echo "{ global:" > .libs/libtest.ver
 cat .libs/libtest.exp | sed -e "s/\(.*\)/\1;/" >> .libs/libtest.ver
 echo "local: *; };" >> .libs/libtest.ver
 gcc -shared  .libs/test.o   -Wl,-soname -Wl,libtest.so.0 -Wl,-version-script
-Wl,.libs/libtest.ver -o .libs/libtest.so.0.0.0
(cd .libs && rm -f libtest.so.0 && ln -s libtest.so.0.0.0 libtest.so.0)
(cd .libs && rm -f libtest.so && ln -s libtest.so.0.0.0 libtest.so)
ar cru .libs/libtest.a  test.o
ranlib .libs/libtest.a
creating libtest.la
(cd .libs && rm -f libtest.la && ln -s ../libtest.la libtest.la)
$ 

-- linked with gcc, and it worked ok.  Note: .libs/libtest.ver file is created
and
-version-script -Wl,.libs/libtest.ver is passed to the linker.

Now I am going to link with g++:

$ libtool --mode=link g++ -o libtest.la -rpath /usr/lib -version-info 0:0:0
-export-symbols-regex '^test' test.lo
rm -fr  .libs/libtest.a .libs/libtest.exp .libs/libtest.la .libs/libtest.lai
.libs/libtest.so .libs/libtest.so.0 .libs/libtest.so.0.0.0 .libs/libtest.ver
generating symbol list for `libtest.la'
/usr/bin/nm -B  .libs/test.o  | sed -n -e 's/^.*[      
]\([ABCDGIRSTW][ABCDGIRSTW]*\)[         ][      ]*\([_A-Za-z][_A-Za-z0-9]*\)$/\1
\2 \2/p' | /bin/sed 's/.* //' | sort | uniq > .libs/libtest.exp
grep -E -e "^test" ".libs/libtest.exp" > ".libs/libtest.expT"
mv -f ".libs/libtest.expT" ".libs/libtest.exp"
g++ -shared -nostdlib /usr/lib/gcc/i586-alt-linux/3.4.4/../../../crti.o
/usr/lib/gcc/i586-alt-linux/3.4.4/crtbeginS.o  .libs/test.o 
-L/usr/lib/gcc/i586-alt-linux/3.4.4 -L/usr/lib/gcc/i586-alt-linux/3.4.4/../../..
-lstdc++ -lm -lc -lgcc_s /usr/lib/gcc/i586-alt-linux/3.4.4/crtendS.o
/usr/lib/gcc/i586-alt-linux/3.4.4/../../../crtn.o  -Wl,-soname -Wl,libtest.so.0
-Wl,-retain-symbols-file -Wl,.libs/libtest.exp -o .libs/libtest.so.0.0.0
i586-alt-linux-g++: /usr/lib/gcc/i586-alt-linux/3.4.4/../../../crti.o: No such
file or directory
i586-alt-linux-g++: /usr/lib/gcc/i586-alt-linux/3.4.4/crtbeginS.o: No such file
or directory
i586-alt-linux-g++: /usr/lib/gcc/i586-alt-linux/3.4.4/crtendS.o: No such file or
directory
i586-alt-linux-g++: /usr/lib/gcc/i586-alt-linux/3.4.4/../../../crtn.o: No such
file or directory
$

-- it failed, but it does not really matter for now.  Note two things:
.libs/libtest.ver is not created;
and -version-script is not passed to the linker.  -Wl,-retain-symbols-file
-Wl,.libs/libtest.exp is used instead.

Now see what happens if I fix the command and use -Wl,-retain-symbols-file:

$ cat .libs/libtest.exp
test
$ g++ -shared -nostdlib .libs/test.o -Wl,-soname -Wl,libtest.so.0
-Wl,-retain-symbols-file -Wl,.libs/libtest.exp -o .libs/libtest.so.0.0.0
$ nm -D .libs/libtest.so.0.0.0
00001244 A __bss_start
         U __gxx_personality_v0
00001244 A _edata
00001244 A _end
000001cc T _test
000001d2 T test
$

You see "_test" is still exported!  However, what I was trying to achieve with
-export-symbols-regex '^test'
is exactly the opposite: "_test" must not be exported.  Thus I infer that
-export-symbols does not work as expected.