将文件保存为特定线程中的字符串
将文件保存为特定线程中的字符串
提问于 2018-02-04 03:20:12
我试图在线程内将一个文本文件保存到C中的字符串中，但我总是得到一个分段错误。这发生在正在创建的线程的实例中。我以前没有使用过线程，所以我不确定这是否是导致问题的原因。
int getCurrentSegmentWordcount(int segment) { //declaring file pointer (value?)
printf("func\n");
char text[1000];
char buffer[150];
FILE *fp = fopen("words.txt", "r");
if(fp == NULL) {
printf("null file");
}
int i = 0;
// while(feof(fp)) {
// text[i++] = fgetc(fp);
// }
// text[i] = '\0'; //set null char to end string
while(fgets(buffer, 150, fp)) {
strcpy(text[i], buffer);
printf("\n\n %s \n\n", text[i]);
i++;
}
getchar();
pthread_exit(NULL);
}下面是我的编译器警告。没有错误，但有多个警告。
assign2.c: In function ‘print_hello_world’:
assign2.c:10:9: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘void *’ [-Wformat=]
printf("Hello World. Greetings from thread %d\n", tid);
^
assign2.c: In function ‘getCurrentSegmentWordcount’:
assign2.c:29:10: warning: passing argument 1 of ‘strcpy’ makes pointer from integer without a cast [-Wint-conversion]
strcpy(text[i], buffer);
^
In file included from assign2.c:4:0:
/usr/include/string.h:125:14: note: expected ‘char * restrict’ but argument is of type ‘char’
extern char *strcpy (char *__restrict __dest, const char *__restrict __src)
^
assign2.c:30:10: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
printf("\n\n %s \n\n", text[i]);
^
assign2.c: In function ‘main’:
assign2.c:46:77: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
status = pthread_create(&threads[i], NULL, getCurrentSegmentWordcount(i), (void * )i);
^
assign2.c:46:46: warning: passing argument 3 of ‘pthread_create’ makes pointer from integer without a cast [-Wint-conversion]
status = pthread_create(&threads[i], NULL, getCurrentSegmentWordcount(i), (void * )i);
^
In file included from assign2.c:1:0:
/usr/include/pthread.h:233:12: note: expected ‘void * (*)(void *)’ but argument is of type ‘int’
extern int pthread_create (pthread_t *__restrict __newthread,
^
assign2.c:52:7: warning: passing argument 1 of ‘exit’ makes integer from pointer without a cast [-Wint-conversion]
exit(NULL);
^
In file included from assign2.c:3:0:
/usr/include/stdlib.h:543:13: note: expected ‘int’ but argument is of type
‘void *’
extern void exit (int __status) __THROW __attribute__ ((__noreturn__));
./assign2exec
Main here. Creating thread 0
func
Makefile:20: recipe for target 'all' failed
make: *** [all] Segmentation fault (core dumped)回答 1
Stack Overflow用户
回答已采纳
发布于 2018-02-04 04:41:39
你要做的第一件事，就是阅读编译器警告，而不是忽略它们。他们在那里是给你暗示你做错了什么，他们不是在那里惹恼你。
函数strcpy具有以下签名：
#include <string.h>
char *strcpy(char *dest, const char *src);从这里可以清楚地看出，它希望dest是指向char数组的指针，src指向的字符串将保存在该数组中。
你声明了char buffer[150];，所以buffer是一个char数组，buffer[i]将返回一个char。因此，您正在将错误的类型传递给strcpy。
编译器会告诉你：
assign2.c: In function ‘getCurrentSegmentWordcount’:
assign2.c:29:10: warning: **passing argument 1 of ‘strcpy’ makes pointer from integer without a cast** [-Wint-conversion]
strcpy(text[i], buffer);你需要有一个2维的char数组或者一个char指针数组来保存它。第一个是最容易编写的：
char text[1000][1000];唯一的问题是它在行数上有一个固定的长度，如果文件有超过1000行，你不能将它们全部存储在缓冲区中。
第二个选项更健壮：
int getCurrentSegmentWordcount(int segment) {
char (*text)[1000] = NULL, char (*tmp)[1000];
...
i = 0;
while(fgets(buffer, sizeof buffer, fp)) {
// removing possible \n from buffer, you probably
// want that
buffer[strcspn(buffer, "\n")] = 0;
tmp = realloc(text, (i+1) * sizeof *tmp);
if(tmp == NULL)
{
// error, cannot continue
free(text);
return;
}
text = tmp;
strcpy(text[i], buffer);
printf("\n\n %s \n\n", text[i]);
i++;
}
...
free(text); // freeing the memory
}而且这个版本甚至可以处理不同长度的行
int getCurrentSegmentWordcount(int segment) {
char **text = NULL, **tmp;
...
i = 0;
while(fgets(buffer, sizeof buffer, fp)) {
// removing possible \n from buffer, you probably
// want that
buffer[strcspn(buffer, "\n")] = 0;
tmp = realloc(text, (i+1) * sizeof *tmp);
if(tmp == NULL)
{
// error, cannot continue
free(text);
return;
}
text = tmp;
text[i] = calloc(strlen(buffer) + 1, 1);
if(text[i] == NULL)
{
// error, free all the allocated memory:
for(int j = 0; j < i; ++j)
free(text[j]);
free(text);
return;
}
strcpy(text[i], buffer);
printf("\n\n %s \n\n", text[i]);
i++;
}
...
// freeing the memory
for(int j = 0; j < i; ++i)
free(text[i]);
free(text);
}我不知道这是不是你的例子，但是你的函数是没有意义的。您将行存储在缓冲区中，但根本不对其执行任何操作。如果你返回了text或者用它做了些什么，这个函数会更有效率。
编译器警告和错误向您显示了需要改进代码的所有行。一行有趣的代码是：
assign2.c:52:7: warning: passing argument 1 of ‘exit’ makes integer from pointer without a cast [-Wint-conversion]
exit(NULL);正确的调用是
exit(0);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/48604348
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