int main() { __res_maybe_init(); // now expects GLIBC_PRIVATE version return 0; }
But for a , use a direct linker undefined reference : undefined symbol --res-maybe-init version glibc-private
// provoke_glibc_private_undef.c void __res_maybe_init(void) __attribute__((weak)); void __res_maybe_init(void) {} // Trick: force reference to the PRIVATE version asm(".symver __res_maybe_init, __res_maybe_init@GLIBC_PRIVATE"); int main() { __res_maybe_init()
Compile and link (the error appears at link time or runtime depending on -z lazy ): } But for a
gcc -c provoke_glibc_private_undef.c gcc -o test provoke_glibc_private_undef.o If linking succeeds (due to weak alias tricks), force by making LD_BIND_NOW=1 ./test .
