从 C 中的函数内部分配字符串数组 [英] Allocate a string array from inside a function in C
问题描述
我有一个函数可以扫描文件并返回行数以及字符串数组中的行数,我的函数如下所示:
I have a function that scans a file and returns the number of the lines along with the lines in a string array, my function looks like this :
int load_lines(char* _file, char** _array){
FILE *infile;
char line_buffer[BUFSIZ];
char line_number;
infile = fopen(_file, "r");
ine_number = 0;
while (fgets(line_buffer, sizeof(line_buffer), infile))
++line_number;
fclose(infile);
_array = malloc (line_number * sizeof(char*));
infile = fopen(_file, "r");
line_number = 0;
while (fgets(line_buffer, sizeof(line_buffer), infile)) {
_array[line_number] = malloc(strlen(line_buffer) + 1);
strcpy(_array[line_number], line_buffer);
//a printf on _array[line_number] works fine here
++line_number;
}
return line_number;
}
当我这样称呼它时:
char** _array;
line_number = load_lines(inname, _array);
_array[0];
我得到一个分段错误,因为在函数返回后似乎没有分配数组.
I get a segmentation fault since the array seems to be not allocated after the return of the function.
推荐答案
当您将参数传递给函数时,函数总是处理该参数的副本.
When you pass an argument into a function, the function always works on a copy of that argument.
因此,在您的情况下,load_lines
正在处理 _array
的副本.原_array
没有修改:
So in your case, load_lines
is working on a copy of _array
. The original _array
is not modified:
char** _array = NULL;
printf("%p
", _array); // Prints "0x0000"
line_number = load_lines(inname, _array);
printf("%p
", _array); // Prints "0x0000"
要修改_array
,你需要传递一个指向它的指针:
To modify _array
, you need to pass a pointer to it:
int load_lines(char* _file, char*** _array){
...
(*array) = malloc (line_number * sizeof(char*));
...
(*array)[line_number] = malloc(strlen(line_buffer) + 1);
}
char** _array = NULL;
line_number = load_lines(inname, &_array);
[然而,任何时候你发现自己需要一个三重指针(即 ***
),是时候重新考虑你的架构了.]
[However, any time you find yourself needing a triple pointer (i.e. ***
), it's time to reconsider your architecture.]
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