运行上面给出的main函数报错error: expected identifier or '(' before '=' token，修正

非常抱歉，这是因为我在拼写log.h和log.c的时候出现了一些错误。在log.h中，我忘记了#include <stdlib.h>，并且在log.c中，我忘记了#include <stdio.h>。这导致编译器无法识别malloc和snprintf函数，从而导致了错误。以下是修正后的代码：

log.h

#ifndef LOG_H
#define LOG_H

#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <time.h>

#define LOG_LEVEL_DEBUG 1
#define LOG_LEVEL_INFO 2
#define LOG_LEVEL_WARN 3
#define LOG_LEVEL_ERROR 4

#define MAX_LOG_SIZE 1024 * 1024  // 日志文件最大大小，单位为字节
#define MAX_LOG_FILES 10  // 最多保留的日志文件数

typedef struct {
    FILE *fp;
    char *filename;
    int level;
    long size;
} log_t;

log_t *log_create(char *filename, int level);
void log_destroy(log_t *log);
void log_write(log_t *log, int level, const char *fmt, ...);
void log_rotate(log_t *log);

#endif

log.c

#include "log.h"

static const char *LOG_LEVEL_STR[] = {"", "DEBUG", "INFO", "WARN", "ERROR"};

log_t *log_create(char *filename, int level) {
    log_t *log = (log_t *) malloc(sizeof(log_t));
    if (!log) {
        fprintf(stderr, "Failed to allocate memory for log\n");
        return NULL;
    }
    log->filename = filename;
    log->level = level;
    log->size = 0;
    log->fp = fopen(log->filename, "a");
    if (!log->fp) {
        fprintf(stderr, "Failed to open log file %s\n", log->filename);
        free(log);
        return NULL;
    }
    return log;
}

void log_destroy(log_t *log) {
    if (log) {
        if (log->fp) {
            fclose(log->fp);
            log->fp = NULL;
        }
        free(log);
    }
}

void log_write(log_t *log, int level, const char *fmt, ...) {
    if (log && log->fp && level >= log->level) {
        va_list args;
        va_start(args, fmt);
        time_t t = time(NULL);
        struct tm *lt = localtime(&t);
        char timestamp[20];
        strftime(timestamp, sizeof(timestamp), "%Y-%m-%d %H:%M:%S", lt);
        fprintf(log->fp, "[%s] [%s] ", timestamp, LOG_LEVEL_STR[level]);
        vfprintf(log->fp, fmt, args);
        fprintf(log->fp, "\n");
        log->size = ftell(log->fp);
        va_end(args);
        if (log->size >= MAX_LOG_SIZE) {
            log_rotate(log);
        }
    }
}

void log_rotate(log_t *log) {
    if (log) {
        fclose(log->fp);
        log->fp = NULL;
        char new_filename[100];
        snprintf(new_filename, sizeof(new_filename), "%s.%d", log->filename, 1);
        remove(new_filename);
        for (int i = MAX_LOG_FILES - 1; i >= 1; i--) {
            char old_filename[100], new_filename[100];
            snprintf(old_filename, sizeof(old_filename), "%s.%d", log->filename, i - 1);
            snprintf(new_filename, sizeof(new_filename), "%s.%d", log->filename, i);
            remove(new_filename);
            rename(old_filename, new_filename);
        }
        rename(log->filename, new_filename);
        log->fp = fopen(log->filename, "a");
        log->size = 0;
    }
}

main.c

#include "log.h"

int main() {
    log_t *log = log_create("test.log", LOG_LEVEL_DEBUG);
    if (!log) {
        return 1;
    }
    for (int i = 0; i < 100000; i++) {
        log_write(log, LOG_LEVEL_INFO, "This is a log message %d", i);
    }
    log_destroy(log);
    return 0;
}

请尝试运行这个修正后的程序，看看是否成功运行了。