我正在C语言中创建一个小程序，该程序将计算用户输入的数字，直到用户输入负数。它使用线程来做到这一点。
我在运行时遇到细分错误，所以我做错了什么，但我不知道到底是什么。
这是我的代码：
/*
* File: main.c
* Author: thomasvanhelden
*
* Created on June 15, 2014, 3:17 AM
*/
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
/**
* Calculates faculty of given number
* Can run as a thread
* @param param The given number
* @return Doesn't return anything
*/
void *fac(void *param) {
int* number = (int*) param;
int faculty = 1;
int i; // counter
printf("De faculteit van %i is: ", number);
for (i = 2; i <= number; i++) {
faculty *= i;
}
printf("%i\n", faculty);
}
/*
*
*/
int main(int argc, char** argv) {
pthread_t **threads;
int getal, numThreads = 0, counter, stop = 0;
// ask for numbers until user enters negative number
while (stop == 0) {
scanf("%i", getal);
if (getal >= 0) {
numThreads++;
threads = realloc(threads, sizeof(pthread_t*) * (numThreads+1));
threads[numThreads - 1] = malloc(sizeof(pthread_t));
// Create the thread
if (pthread_create(&threads[numThreads - 1], NULL, fac, &getal)) {
// something went wrong
printf("Error creating thread %i!\n", numThreads);
return 1;
}
} else {
// User entered negative number and wants to stop
stop = 1;
}
}
// join all the threads
for (counter = 0; counter < numThreads; counter++) {
if (pthread_join(threads[counter], NULL)) {
printf("Something went wrong joining thread %i\n", counter + 1);
}
}
return (EXIT_SUCCESS);
}
我认为您的意思是“阶乘”？无论如何，您的代码存在多个问题。即使没有启用严格的标志，我也会收到以下警告：
fac.c:23:40: warning: format specifies type 'int' but the argument has type 'int *' [-Wformat]
printf("De faculteit van %i is: ", number);
~~ ^~~~~~
fac.c:25:19: warning: ordered comparison between pointer and integer ('int' and 'int *')
for (i = 2; i <= number; i++) {
~ ^ ~~~~~~
fac.c:30:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
fac.c:41:21: warning: format specifies type 'int *' but the argument has type 'int' [-Wformat]
scanf("%i", getal);
~~ ^~~~~
fac.c:49:32: warning: incompatible pointer types passing 'pthread_t **' (aka 'struct _opaque_pthread_t ***') to
parameter of type 'pthread_t *' (aka 'struct _opaque_pthread_t **'); remove &
[-Wincompatible-pointer-types]
if (pthread_create(&threads[numThreads - 1], NULL, fac, &getal)) {
^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/pthread.h:310:42: note: passing argument to parameter here
int pthread_create(pthread_t * __restrict, const pthread_attr_t * __restrict,
^
fac.c:63:26: warning: incompatible pointer types passing 'pthread_t *' (aka 'struct _opaque_pthread_t **') to
parameter of type 'pthread_t' (aka 'struct _opaque_pthread_t *'); dereference with *
[-Wincompatible-pointer-types]
if (pthread_join(threads[counter], NULL)) {
^~~~~~~~~~~~~~~~
*
/usr/include/pthread.h:333:28: note: passing argument to parameter here
int pthread_join(pthread_t , void **) __DARWIN_ALIAS_C(pthread_join);
^
6 warnings generated.
照原样，如果您在下运行程序gdb，则在输入数字后它会崩溃：
...
4
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000000
0x00007fff92c1401a in __svfscanf_l ()
(gdb) bt
#0 0x00007fff92c1401a in __svfscanf_l ()
#1 0x00007fff92c0c0eb in scanf ()
#2 0x0000000100000d72 in main (argc=1, argv=0x7fff5fbffa18) at fac.c:41
查看堆栈跟踪时bt，我们立即看到它在您调用的第41行崩溃了scanf()。而且，如果您回顾一下编译器警告，它会告诉您它期望一个，int*但是您只传递了int。这是因为scanf需要一个指针才能用用户输入来修改变量。
如果您修复了所有其余的警告，则您的代码将起作用。
number在fac函数中取消引用时要使用它的值threads，以NULL使realloc分配将工作（这是另外未定义的，大概非为零，因此缓冲区永远不会（再）pthread_create与pthread_join这样的价值/指针预期的签名相匹配的呼叫需要更新完成上述更改后，我可以按预期运行它：
$ ./fac_fixed
3
De faculteit van 3 is: 6
4
De faculteit van 4 is: 24
5
De faculteit van 5 is: 120
6
De faculteit van 6 is: 720
7
De faculteit van 7 is: 5040
8
De faculteit van 8 is: 40320
9
De faculteit van 9 is: 362880
12
De faculteit van 12 is: 479001600
-1
至于代码的结构，我不明白为什么仍然要创建一个线程数组，因为您一次只按顺序计算一个。您实际上只需要最多一个工作线程，但是由于main除了阻塞连接外什么也不做，因此它实际上并不需要在线程中。但是至少它不会崩溃！
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