 whether weak symbols during dynamic linking at runtime lose their semantics or not.The GNU Compiler Collection and the Solaris Studio C compiler share the same syntax for annotating symbols as weak, namely a special #pragma, codice_1, and, alternatively, a function and variable attribute, codice_2.// function declaration

int power2(int x);
// function declaration

int __attribute__((weak)) power2(int x);

int power2(int x) __attribute__((weak));

// variable declaration;
extern int __attribute__((weak)) global_var;

The nm command identifies weak symbols in object files, libraries, and executables.