pthread 编程新手，在处理 C++&C 混合代码时遇到此错误。
我所做的是在c++代码创建的线程中调用c代码。线程中使用了一个静态布尔指针is_center，当线程完成时应该释放。
但是我注意到，每次程序处理到 c 函数时，布尔指针的值都会改变，然后由于 free() 而发生分段错误。并且仅在使用 c 代码时才会出现问题。去掉c代码，多线程c++部分运行良好。
详细代码如下：
static bool *is_center;
// omit other codes in between ...
void streamCluster( PStream* stream)
{
// some code here ...
while(1){
// some code here ...
is_center = (bool*)calloc(points.num,sizeof(bool));
// start the parallel thread here.
// the c code is invoked in this function.
localSearch(&points,kmin, kmax,&kfinal); // parallel
free(is_center);
}
而使用parallel的函数如下（我的c代码在每个线程中调用）：
void localSearch( Points* points, long kmin, long kmax, long* kfinal ) {
pthread_barrier_t barrier;
pthread_t* threads = new pthread_t[nproc];
pkmedian_arg_t* arg = new pkmedian_arg_t[nproc];
pthread_barrier_init(&barrier,NULL,nproc);
for( int i = 0; i < nproc; i++ ) {
arg[i].points = points;
arg[i].kmin = kmin;
arg[i].kmax = kmax;
arg[i].pid = i;
arg[i].kfinal = kfinal;
arg[i].barrier = &barrier;
pthread_create(threads+i,NULL,localSearchSub,(void*)&arg[i]);
}
for ( int i = 0; i < nproc; i++) {
pthread_join(threads[i],NULL);
}
delete[] threads;
delete[] arg;
pthread_barrier_destroy(&barrier);
}
最后调用我的c代码的函数：
void* localSearchSub(void* arg_) {
int eventSet = PAPI_NULL;
begin_papi_thread(&eventSet);
pkmedian_arg_t* arg= (pkmedian_arg_t*)arg_;
pkmedian(arg->points,arg->kmin,arg->kmax,arg->kfinal,arg->pid,arg->barrier);
end_papi_thread(&eventSet);
return NULL;
}
从gdb，我得到的is_center是：
Breakpoint 2, localSearchSub (arg_=0x600000000000bc40) at streamcluster.cpp:1711
1711 end_papi_thread(&eventSet);
(gdb) s
Hardware watchpoint 1: is_center
Old value = (bool *) 0x600000000000bba0
New value = (bool *) 0xa93f3
0x400000000000d8d1 in localSearchSub (arg_=0x600000000000bc40) at streamcluster.cpp:1711
1711 end_papi_thread(&eventSet);
有什么建议么？提前致谢！
关于代码的一些新信息：对于 c 代码，我使用的是 PAPI 包。我编写了自己的 papi 包装器来初始化和读取系统计数器。代码如下：
void begin_papi_thread(int* eventSet)
{
int thread_id = pthread_self();
// Events
if (PAPI_create_eventset(eventSet)) {
PAPI_perror(return_value, error_string, PAPI_MAX_STR_LEN);
printf("*** ERROR *** Failed to create event set for thread %d: %s\n.", thread_id, error_string);
}
if((return_value = PAPI_add_events(*eventSet, event_code, event_num)) != PAPI_OK)
{
printf("*** ERROR *** Failed to add event for thread %d: %d.\n", thread_id, return_value);
}
// Start counting
if ((return_value = PAPI_start(*eventSet)) != PAPI_OK) {
PAPI_perror(return_value, error_string, PAPI_MAX_STR_LEN);
printf("*** ERROR *** PAPI failed to start the event for thread %d: %s.\n", thread_id, error_string);
}
}
void end_papi_thread(int* eventSet)
{
int thread_id = pthread_self();
int i;
long long * count_values = (long long*)malloc(sizeof(long long) * event_num);
if (PAPI_read(*eventSet, count_values) != PAPI_OK)
printf("*** ERROR *** Failed to load count values.\n");
if (PAPI_stop(*eventSet, &dummy_values) != PAPI_OK) {
PAPI_perror(return_value, error_string, PAPI_MAX_STR_LEN);
printf("*** ERROR *** PAPI failed to stop the event for thread %d: %s.\n", thread_id, error_string);
return;
}
if(PAPI_cleanup_eventset(*eventSet) != PAPI_OK)
printf("*** ERROR *** Clean up failed for the thread %d.\n", thread_id);
}