mheffner

$ objdump -t /lib64/libpthread.so.0  | grep pthread_cond_wait
0000000000000000 l    df *ABS*       0000000000000000              old_pthread_cond_wait.c
0000003cf900b240 l     F .text       00000000000001f7              __pthread_cond_wait
0000003cf900b8f0 l     F .text       0000000000000098              __pthread_cond_wait_2_0
0000003cf900b240 g     F .text       00000000000001f7              pthread_cond_wait@@GLIBC_2.3.2
0000003cf900b8f0 g     F .text       0000000000000098              pthread_cond_wait@GLIBC_2.2.5

mheffner

$ objdump -t condwait_test | grep pthread_cond_wait
0000000000000000       F *UND*    0000000000000000              pthread_cond_wait@@GLIBC_2.3.2

mheffner

$ objdump -t /lib64/libpthread.so.0  | grep pthread_cond_wait
0000000000000000 l    df *ABS*       0000000000000000              old_pthread_cond_wait.c
0000003cf900b240 l     F .text       00000000000001f7              __pthread_cond_wait
0000003cf900b8f0 l     F .text       0000000000000098              __pthread_cond_wait_2_0
0000003cf900b240 g     F .text       00000000000001f7              pthread_cond_wait@@GLIBC_2.3.2
0000003cf900b8f0 g     F .text       0000000000000098              pthread_cond_wait@GLIBC_2.2.5

mheffner

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <pthread.h>

static int (*condwait_internal)(pthread_cond_t *cond, pthread_mutex_t *mutex);

void __attribute__ ((constructor)) init(void);

mheffner

$ gcc -g3 -Wall -fPIC -shared -o condwait_wrap.so condwait_wrap.c -ldl -lpthread

$ gcc -g3 -Wall -o condwait_test condwait_test.c  -lpthread

$ LD_PRELOAD=./condwait_wrap.so ./condwait_test
Calling func condwait with cond: 0x600d80, mutex: 0x600dc0.....got it!
Thread exiting

mheffner

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <pthread.h>

static int (*condwait_internal_225)(pthread_cond_t *cond,
				    pthread_mutex_t *mutex);

static int (*condwait_internal_232)(pthread_cond_t *cond,

mheffner

$ gcc -g3 -Wall -fPIC -shared -o condwait_wrap.so condwait_wrap.c -ldl -lpthread
/usr/bin/ld: condwait_wrap.so: version node not found for symbol pthread_cond_wait@@GLIBC_2.3.2
/usr/bin/ld: failed to set dynamic section sizes: Bad value
collect2: ld returned 1 exit status
Exit 1

mheffner

GLIBC_2.2.5 {
        global:
                pthread_cond_wait;
        local:
                *;
};

GLIBC_2.3.2 {
        global:
                pthread_cond_wait;

mheffner

$ gcc -g3 -Wall -fPIC -shared -o condwait_wrap.so condwait_wrap.c -ldl -lpthread -Wl,--version-script -Wl,VERSION.txt

$ LD_PRELOAD=./condwait_wrap.so ./condwait_test
Calling condwait v. 2.3.2 with cond: 0x600d80, mutex: 0x600dc0.....got it!
Thread exiting

$ objdump -t condwait_wrap.so | grep pthread_cond_wait
000000000000074a l     F .text	000000000000006c              pthread_cond_wait_225
00000000000007b6 l     F .text	000000000000006c              pthread_cond_wait_232
00000000000007b6 g     F .text	000000000000006c              pthread_cond_wait@@GLIBC_2.3.2

mheffner

/* ab.h -- External API for libab. */
#ifndef __AB_H__
#define  __AB_H__

const char *ab_get_string(void);

#endif /* ! __AB_H__ */