invalid conversion from 'void* (*)()' to 'void* (*)(void*)'
2013-11-01 08:36
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void *thread1()
if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0)
提示:invalid conversion from 'void* (*)()' to 'void* (*)(void*)'
=============
改成: void *thread1(void *)
void* (*)(void*): (*)表示这里需要一个函数指针, (void*)表示参数类型需要为void*
参考:
http://groups.google.com/group/comp.programming.threads/browse_thread/thread/8fddb216a36daa87/b03dda5b143e8260?#b03dda5b143e8260
The pthread_* functions are C language. The C++ prototype for a thread function is
extern "C" void *thread_function(void *);
===============================================================================================
void main_thread ( void *ptr )
{
char *message1 = "Thread 1";
char *message2 = "Thread 2";
pthread_t thread3, thread4;
int iret3, iret4;
iret3 = pthread_create(&thread3, NULL, (void *)&print_message_function, (void *) message1);
iret4 = pthread_create(&thread4, NULL, (void *)&print_message_function, (void *) message2);
}
void print_message_function( void *ptr )
{
char *message;
message = (char *) ptr;
printf("%s \n", message);
}
以上这段代码在用g++编译是会有如下错误:
invalid conversion from `void*' to `void*(*)(void*)
我们注意在Posix定义建立线程函数的原型:
extern int pthread_create (pthread_t *__restrict __threadp,
__const
pthread_attr_t *__restrict __attr,
void
*(*__start_routine) (void *),
void
*__restrict __arg) __THROW;
这个call中的第三个参数是载入一个函数,这个函数有一个参数可以传入,返回一个 通用指针。
我们再来看看原来函数中是怎样调用这一原型的,基本上就是类似一下的调用方式:
(void *)&main_thread
这个表达式的含义:取一个指向函数main_thread的指针,然后将其转换为一个通用指针。
这就是说显然上述两个事情并非同一个事情,故而正确的调用方式是
iret3 = pthread_create(&thread3, NULL, print_message_function, (void *) message1);
处理函数的定义如下:
void* print_message_function( void *ptr )
值得注意的是在gcc编译时不会出错,但是用g++就会有问题,究其原因就是C语言编译器允许隐含性的将一个通用指针转换为任意类型的指针,而C++不允许。
if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0)
提示:invalid conversion from 'void* (*)()' to 'void* (*)(void*)'
=============
改成: void *thread1(void *)
void* (*)(void*): (*)表示这里需要一个函数指针, (void*)表示参数类型需要为void*
参考:
http://groups.google.com/group/comp.programming.threads/browse_thread/thread/8fddb216a36daa87/b03dda5b143e8260?#b03dda5b143e8260
The pthread_* functions are C language. The C++ prototype for a thread function is
extern "C" void *thread_function(void *);
===============================================================================================
void main_thread ( void *ptr )
{
char *message1 = "Thread 1";
char *message2 = "Thread 2";
pthread_t thread3, thread4;
int iret3, iret4;
iret3 = pthread_create(&thread3, NULL, (void *)&print_message_function, (void *) message1);
iret4 = pthread_create(&thread4, NULL, (void *)&print_message_function, (void *) message2);
}
void print_message_function( void *ptr )
{
char *message;
message = (char *) ptr;
printf("%s \n", message);
}
以上这段代码在用g++编译是会有如下错误:
invalid conversion from `void*' to `void*(*)(void*)
我们注意在Posix定义建立线程函数的原型:
extern int pthread_create (pthread_t *__restrict __threadp,
__const
pthread_attr_t *__restrict __attr,
void
*(*__start_routine) (void *),
void
*__restrict __arg) __THROW;
这个call中的第三个参数是载入一个函数,这个函数有一个参数可以传入,返回一个 通用指针。
我们再来看看原来函数中是怎样调用这一原型的,基本上就是类似一下的调用方式:
(void *)&main_thread
这个表达式的含义:取一个指向函数main_thread的指针,然后将其转换为一个通用指针。
这就是说显然上述两个事情并非同一个事情,故而正确的调用方式是
iret3 = pthread_create(&thread3, NULL, print_message_function, (void *) message1);
处理函数的定义如下:
void* print_message_function( void *ptr )
值得注意的是在gcc编译时不会出错,但是用g++就会有问题,究其原因就是C语言编译器允许隐含性的将一个通用指针转换为任意类型的指针,而C++不允许。
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