I wonder if someone knows what is the rationale behind linking function calls of the POSIX threads library at link-time vs. run-time.

For example, if I create the following program:

Code:

#include <pthread.h>

void noop() {
  return;
}

int main() {
  pthread_self();
  pthread_atfork(noop, noop, noop);
  return 0;
}

and compile it on Ubuntu version 10.10 with gcc version 4.4.5 using:

Code:

gcc -o test -lpthread -pthread test.c

then the pthread_self symbol is linked (dynamically) at run-time, while the pthread_atfork symbol is linked (statically) at link-time.

Further, there is the case of pthread_equal, code of which might be inlined (assuming __USE_EXTERN_INLINES is defined).

My project plans to use a run-time interposition based wrapper for the POSIX threads library functions to monitor and control interaction of a program with the pthreads library. Cases such as pthread_atfork and pthread_equal are giving me a headache :-).

--Jiri