C语言 逐行存储文件的函数会产生奇怪的结果

Question

我写了一个函数，它接受一个文件并将每一行存储在一个字符串数组中。

以下是涉及的功能：

char **get_lines(FILE *file) {
int MAX_LINE_LENGTH = 2048;
int num_lines = 19;
char **lines = malloc(sizeof(char *) * num_lines);
// Make sure to start at the beginning of the file
fseek(file, 0L, SEEK_SET);
char *line = malloc(MAX_LINE_LENGTH);
int i = 0; // index counter for lines
while (fgets(line, MAX_LINE_LENGTH, file)) {
// Only add to lines if the line is not a single newline character
if (strcmp(line, "n")) {
int len = strlen(line);
// Remove the last character as
// it should always be a newline character
if (len < MAX_LINE_LENGTH) {
line[len-1] = '';
}
lines[i] = malloc(strlen(line));
lines[i++] = line;
printf("%sn", lines[i-1]); // This prints the lines correctly.
}
}
for (int x=0; x < num_lines; x++) {
// This prints strings containing only a newline character.
printf("%s", lines[x]); 
}
return lines;
}

令我困惑的是，如果我在将行添加到数组后立即打印该行(在 while 循环内(，则会打印正确的字符串。但是，如果我在定义完lines后打印每一行(在 while 循环之外(，它只会打印包含换行符的字符串。

可能是什么原因造成的？

编辑在不修改程序后，现在第二个 printf 语句只向控制台打印任何内容。

如果它有帮助，我正在使用CLion。

Answer 1

代码正在泄漏内存，因为它忽略了malloc内部循环，并且它将相同的行地址分配给行[i]

char **get_lines(FILE *file) {
int MAX_LINE_LENGTH = 2048;
int num_lines = 19;
char **lines = malloc(sizeof(char *) * num_lines);
// Make sure to start at the beginning of the file
fseek(file, 0L, SEEK_SET);
char *line = malloc(MAX_LINE_LENGTH);
int i = 0; // index counter for lines
while (fgets(line, MAX_LINE_LENGTH, file)) {
// Only add to lines if the line is not a single newline character
if (strcmp(line, "n")) {
int len = strlen(line);
// Remove the last character as
// it should always be a newline character
if (len < MAX_LINE_LENGTH) {
line[len-1] = '';
}
lines[i] = malloc(strlen(line));
strncpy(lines[i], line, len);
i++;
printf("%sn", lines[i-1]); // This prints the lines correctly.
}
}
for (int x=0; x < num_lines; x++) {
// This prints strings containing only a newline character.
printf("%s", lines[x]); 
}
return lines;
}