C++ C代码在字符串中删除不区分大小写的子字符串的问题

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

int erase_once(char *input_string, const char *substring, int case_sensitive) {
    size_t string_length = strlen(input_string);
    size_t substring_length = strlen(substring);

    if (string_length < substring_length || substring_length == 0) return 0;

    size_t i;
    for (i = 0; i < string_length - substring_length + 1; i++) {
        int match_found = 1;

        for (size_t j = i; j < i + substring_length; j++) {
            if ((case_sensitive == 0 &&
                 tolower(input_string[j]) != tolower(substring[j-i])) ||
                input_string[j] != substring[j-i]) {
                match_found = 0;
                break;
            }
        }

        if (!match_found) continue;

        for (; i < string_length - substring_length; i++) {
            input_string[i] = input_string[i + substring_length];
        }
        input_string[i] = '\0';

        return 1;
    }

    return 0;
}

int erase(char *input_string, const char *substring, int case_sensitive) {
    int count;
    for (count = 0; erase_once(input_string, substring, case_sensitive); count++);
    return count;
}

int main(void) {
    char main_string[] = "abcdef cde AbCDE";
    const char *substring_to_erase = "abc";

    erase(main_string, substring_to_erase, 0);
    printf("%s\n", main_string);

    return 0;
}

我try 通过将变量INT CASE_SENSITIVE设置为区分大小写；当变量为0时，它不区分大小写；当变量为1时，它区分大小写，例如: 对于输入"ABCDEF CDE ABCDE"和子字符串"ABC"，如果为1，则应返回 -"def CDE ABCDE"； 对于相同的输入，并且将区分大小写设置为0 它应该返回"def CDE DE" 另一个例子是字符串 XYXyXYXY和子字符串xy，并且敏感设置为0，它应该返回 空字符串

但是没有，你能帮我找出错误吗？