std：：线程参数在转换为rvalue后必须是可调用的。
std：：线程参数在转换为rvalue后必须是可调用的。
提问于 2021-04-26 14:39:22
我正在尝试创建两个线程，它们可以处理浮点数组。Howere编译器给出了以下错误：
/usr/include/c++/9/thread: In instantiation of ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(bool*, float*, float*, float*); _Args = {bool*, float (*)[10], float (*)[10], float (*)[10]}; <template-parameter-1-3> = void]’:
main.cpp:16:66: required from here
/usr/include/c++/9/thread:120:44: error: static assertion failed: std::thread arguments must be invocable after conversion to rvalues
120 | typename decay<_Args>::type...>::value,
| ^~~~~
/usr/include/c++/9/thread: In instantiation of ‘struct std::thread::_Invoker<std::tuple<void (*)(bool*, float*, float*, float*), bool*, float (*)[10], float (*)[10], float (*)[10]> >’:
/usr/include/c++/9/thread:131:22: required from ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(bool*, float*, float*, float*); _Args = {bool*, float (*)[10], float (*)[10], float (*)[10]}; <template-parameter-1-3> = void]’
main.cpp:16:66: required from here
/usr/include/c++/9/thread:243:4: error: no type named ‘type’ in ‘struct std::thread::_Invoker<std::tuple<void (*)(bool*, float*, float*, float*), bool*, float (*)[10], float (*)[10], float (*)[10]> >::__result<std::tuple<void (*)(bool*, float*, float*, float*), bool*, float (*)[10], float (*)[10], float (*)[10]> >’
243 | _M_invoke(_Index_tuple<_Ind...>)
| ^~~~~~~~~
/usr/include/c++/9/thread:247:2: error: no type named ‘type’ in ‘struct std::thread::_Invoker<std::tuple<void (*)(bool*, float*, float*, float*), bool*, float (*)[10], float (*)[10], float (*)[10]> >::__result<std::tuple<void (*)(bool*, float*, float*, float*), bool*, float (*)[10], float (*)[10], float (*)[10]> >’
247 | operator()()
| ^~~~~~~~
/usr/include/c++/9/thread: In instantiation of ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(float*); _Args = {float (*)[10]}; <template-parameter-1-3> = void]’:
main.cpp:17:43: required from here
/usr/include/c++/9/thread:120:44: error: static assertion failed: std::thread arguments must be invocable after conversion to rvalues
120 | typename decay<_Args>::type...>::value,
| ^~~~~
/usr/include/c++/9/thread: In instantiation of ‘struct std::thread::_Invoker<std::tuple<void (*)(float*), float (*)[10]> >’:
/usr/include/c++/9/thread:131:22: required from ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(float*); _Args = {float (*)[10]}; <template-parameter-1-3> = void]’
main.cpp:17:43: required from here
/usr/include/c++/9/thread:243:4: error: no type named ‘type’ in ‘struct std::thread::_Invoker<std::tuple<void (*)(float*), float (*)[10]> >::__result<std::tuple<void (*)(float*), float (*)[10]> >’
243 | _M_invoke(_Index_tuple<_Ind...>)
| ^~~~~~~~~
/usr/include/c++/9/thread:247:2: error: no type named ‘type’ in ‘struct std::thread::_Invoker<std::tuple<void (*)(float*), float (*)[10]> >::__result<std::tuple<void (*)(float*), float (*)[10]> >’
247 | operator()()
| ^~~~~~~~我以为我忘记了dma线程的一些ctor参数，但事实并非如此。这是我的代码：
#include <iostream>
#include <cstdint>
#include <thread>
void dma_service(bool*, float*, float*, float*);
void live_audio(float*);
void live_draw(float*);
constexpr int d_size = 10;
float data[d_size];
float pwm_cp[d_size];
float fft_cp[d_size];
bool drdy = 0;
std::thread dma_thrd(dma_service, &drdy, &data, &pwm_cp, &fft_cp);
std::thread audio_thrd(live_draw, &pwm_cp);
int main(){
for (auto i = 0; i < d_size; i++)
{
data[i] = 0;
pwm_cp[i] = 0;
}
printf("Hello, World!\n");
drdy = 1;
int k = 3;
while(k-->0)
{
audio_thrd.join();
printf("\n\n\n");
for (auto i = 0; i < d_size; i++)
{
data[i]++;
}
drdy = 1;
}
}
void dma_service(bool* flag, float* d_array, float* pwm_array, float* fft_array) {
while (!flag) ;
for (auto i = 0; i < d_size; i++)
{
pwm_array[i] = d_array[i];
fft_array[i] = d_array[i];
}
flag = 0;
}
void live_audio(float* pwm_array) {
dma_thrd.join();
printf("Audio Array:\n");
for (auto i = 0; i < d_size; i++)
{
printf("PWM_CP[%d] %f\n", i, pwm_array[i]);
}
}我对lambda函数没有太多的经验，所以我不知道这里是否需要它们(并且很乐意避免它们)。谢谢你的建议！
回答 2
Stack Overflow用户
回答已采纳
发布于 2021-04-26 14:50:07
给定float data[d_size];，&data被推断为“指向数组的指针”类型。这与float*参数不匹配。
您可以简单地省略&，然后数组到指针的衰减将开始，类型将匹配。
std::thread dma_thrd(dma_service, &drdy, data, pwm_cp, fft_cp);
std::thread audio_thrd(live_draw, pwm_cp);或者传递第一个元素的地址：
std::thread dma_thrd(dma_service, &drdy, &data[0], &pwm_cp[0], &fft_cp[0]);
std::thread audio_thrd(live_draw, &pwm_cp[0]);请注意，这不足以使程序工作。我看到它缺少线程同步，在全局范围启动这样的线程是有问题的，因为它们将在main()之前启动。另外，循环中的join()不能正常工作，因为join()只能执行一次。
Stack Overflow用户
发布于 2021-04-26 14:49:51
要具有匹配的参数，您需要：
constexpr int d_size = 10;
float data[d_size];
float pwm_cp[d_size];
float fft_cp[d_size];
bool drdy = 0;
void dma_service(bool*, float*, float*, float*);
std::thread dma_thrd(dma_service, &drdy, &data[0], &pwm_cp[0], &fft_cp[0]);或
constexpr int d_size = 10;
float data[d_size];
float pwm_cp[d_size];
float fft_cp[d_size];
bool drdy = 0;
void dma_service(bool*, float(*)[10], float(*)[10], float(*)[10]);
std::thread dma_thrd(dma_service, &drdy, &data, &pwm_cp, &fft_cp);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/67268682
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