c++ - How to export specific symbol from executables in GNU/Linux -


while loading dynamic libraries ::dlopen(), exporting symbols executables can done -rdynamic option, exports symbols of executable, results in bigger binary size.

is there way export specific function(s)?

for example, have testlib.cpp , main.cpp below:

testlib.cpp

extern void func_export(int i);  extern "c" void func_test(void) {   func_export(4); }

main.cpp

#include <cstdio> #include <dlfcn.h>  void func_export(int i) {   ::fprintf(stderr, "%s: %d\n", __func__, i); }  void func_not_export(int i) {   ::fprintf(stderr, "%s: %d\n", __func__, i); }  typedef void (*void_func)(void);  int main(void) {   void* handle = null;   void_func func = null;   handle = ::dlopen("./libtestlib.so", rtld_now | rtld_global);   if (handle == null) {     fprintf(stderr, "unable open lib: %s\n", ::dlerror());     return 1;   }   func = reinterpret_cast<void_func>(::dlsym(handle, "func_test"));    if (func == null) {     fprintf(stderr, "unable symbol\n");     return 1;   }   func();   return 0; }

compile:

g++ -fpic -shared -o libtestlib.so testlib.cpp g++ -c -o main.o main.cpp

i want func_export used dynamic library, hide func_not_export.

if link -rdynamic, g++ -o main -ldl -rdynamic main.o , both functions exported.

if not link -rdynamic, g++ -o main_no_rdynamic -ldl main.o , got runtime error unable open lib: ./libtestlib.so: undefined symbol: _z11func_exporti

is possible achieve requirement export specific function?

is there way export specific function(s)?

we needed functionality, , added --export-dynamic-symbol option gold linker here.

if using gold, build recent version , you'll set.

if not using gold, perhaps should -- it's faster, , has functionality need.


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