I went through this post Hiding symbol names in library but still could not get proper conclusion
1) Filename : lib_mylib.h
int fun();
int fun1(void);
int fun2(void);
2) Filename: lib_mylib.c */
#include <stdio.h>
int fun() {
return 2;
}
int fun1(void) {
return 2;
}
int fun2(void) {
return 2;
}
3) File :my_lib_shared.c
#include "my_lib.h"
int foo(void) {
return fun() + 4;
}
4) File: my_lib_shared.h
int foo();
5) File driver.c
/* filename: driver.c */
#include "my_lib.h"
#include "my_lib_shared.h"
#include <stdio.h>
int main() {
int x = foo() ;
return 0;
}
If I execute following steps
1)gcc -fPIC -fvisibility=hidden -c my_lib.c -o lib_mylib.o
2)gcc -fPIC -fvisibility=hidden -shared -o libMyLibHidden.so lib_mylib.o
3)gcc -fPIC -c my_lib_shared.c -o my_lib_shared.o
4)gcc -shared -o libMyShared2.so my_lib_shared.o
5)gcc -L. -Wall -o test_hidden driver.c -lMyLibHidden -lMyShared2
The output of objdump is as
objdump -T libMyLibHidden.so
libMyLibHidden.so: file format elf64-x86-64
DYNAMIC SYMBOL TABLE:
0000000000000448 l d .init 0000000000000000 .init
0000000000000000 w D *UND* 0000000000000000 __gmon_start__
0000000000000000 w D *UND* 0000000000000000 _Jv_RegisterClasses
0000000000000658 g DF .fini 0000000000000000 Base _fini
0000000000000000 w D *UND* 0000000000000000 _deregisterTMCloneTable
0000000000000000 w D *UND* 0000000000000000 _ITM_registerTMCloneTable
0000000000000000 w DF *UND* 0000000000000126 GLIBC_2.2.5 _cxa_finalize
0000000000200938 g D *ABS* 0000000000000000 Base __bss_start
0000000000200948 g D *ABS* 0000000000000000 Base _end
0000000000200938 g D *ABS* 0000000000000000 Base _edata
0000000000000448 g DF .init 0000000000000000 Base _init
I did not any reference of functions of fun, fun1 and fun2 in the above objdump
and I get following error at final linking step
/tmp/ccMsEpFq.o: In function main':
driver.c:(.text+0xe): undefined reference tofun'
collect2: error: ld returned 1 exit status
When I make static library from lib_mylib.c
1)gcc -g -fvisibility=hidden -c my_lib.c -o lib_mylib.o
2)ar rcs libMylib_static_hidden.a lib_mylib.o
3)gcc -g -fvisibility=hidden -c -fPIC my_lib_shared.c -o my_lib_shared.o
4)gcc -g -shared -o libMyShare.so my_lib_shared.o
5)gcc -g driver.c -L . -Wall -o test_static_hidden -lMyShare -lMylib_static_hidden
and I get following objdump
objdump -t libMylib_static_hidden.a
In archive libMylib_static_hidden.a:
lib_mylib.o: file format elf64-x86-64
SYMBOL TABLE:
0000000000000000 l df *ABS* 0000000000000000 my_lib.c
0000000000000000 l d .text 0000000000000000 .text
0000000000000000 l d .data 0000000000000000 .data
0000000000000000 l d .bss 0000000000000000 .bss
0000000000000000 l d .debug_abbrev 0000000000000000 .debug_abbrev
0000000000000000 l d .debug_info 0000000000000000 .debug_info
0000000000000000 l d .debug_line 0000000000000000 .debug_line
0000000000000000 l d .debug_frame 0000000000000000 .debug_frame
0000000000000000 l d .eh_frame 0000000000000000 .eh_frame
0000000000000000 l d .debug_pubnames 0000000000000000 .debug_pubnames
0000000000000000 l d .debug_aranges 0000000000000000 .debug_aranges
0000000000000000 l d .debug_str 0000000000000000 .debug_str
0000000000000000 l d .note.GNU-stack 0000000000000000 .note.GNU-stack
0000000000000000 l d .comment 0000000000000000 .comment
0000000000000000 g F .text 000000000000000b .hidden fun
000000000000000b g F .text 000000000000000b .hidden fun1
0000000000000016 g F .text 000000000000000b .hidden fun2
When I final link the library
5)gcc -g driver.c -L . -Wall -o test_static_hidden -lMylib_static_hidden -lMyShare
I get following linker error
test_static_hidden: hidden symbol `fun' in libMylib_static_hidden.a(lib_mylib.o) is referenced by DSO /tools/linux64/gcc-4.0.2/bin/ld: final link failed: Nonrepresentable section on output I need guidance on why hidden visibility does not get applied when I make shared libraries and why I get undefined reference in case of linking shared library libMyLibHidden.so
I
