全局结构内存错误

Question

我的程序使用 libconfig 从配置文件中读取并将值保存到全局结构。它工作正常，但 valgrind 说有错误。并且错误仅针对 char 指针变量显示。该错误是什么以及如何解决？谢谢

#include <stdio.h>
#include <libconfig.h>
#include "stdlib.h"
#define conf_file "myconf"

struct setting_data
{
    int number;
    const char* timeformat;
};
struct setting_data conf_data;
void read_config();
int main(){
    read_config();
    printf("%d @ %p\n", conf_data.number,&conf_data.number);
    printf("%s @ %p\n", conf_data.timeformat,&conf_data.timeformat);

}

void read_config(){
    config_t cfg;
    // config_setting_t *rules, *settings,*m_number,*device,*sendduration,*pin_code;
    config_init(&cfg);

    if(! config_read_file(&cfg, conf_file))
    {
        fprintf(stderr, "%s:%d - %s\n", config_error_file(&cfg),
                config_error_line(&cfg), config_error_text(&cfg));
        config_destroy(&cfg);
        exit(1);
    }
    // conf_data.number        = config_setting_get_int   (config_lookup(&cfg, "number"       ));
    config_lookup_int(&cfg,"number",&conf_data.number);
    config_lookup_string(&cfg, "timeformat", &conf_data.timeformat);
    config_destroy(&cfg);
}

==8238== Invalid read of size 1

==8238== at 0x50AFBC9: _IO_file_xsputn@@GLIBC_2.2.5 (fileops.c:1317)

==8238== by 0x5083972: vfprintf (vfprintf.c:1629)

==8238== by 0x508C269: printf (printf.c:35)

==8238== by 0x400993: main (test.c:16)

....

==8238== Address 0x53cdb0c is 12 bytes inside a block of size 15 free'd

==8238== ERROR SUMMARY: 43 errors from 5 contexts (suppressed: 4 from 4)

Answer 1

libconfig 向您传递一个指向其内部字符串存储的指针，用于 timeformat 值。当您执行 config_destroy() 导致全局结构的时间格式指针无效时，它会被释放。为避免这种情况 strdup() libconfig 返回给您的时间格式字符串：

const char *time_str;
config_lookup_string(&cfg, "timeformat", &time_str);
conf_data.timeformat = strdup(time_str);
config_destroy(&cfg);
/* conf_data.timeformat is still valid */

Answer 2

来自 the libconfig api manual

Storage for the string returned by config_lookup_string() is managed by the library and released automatically when the setting is destroyed or when the setting's value is changed; the string must not be freed by the caller.

所以config_lookup_string()返回的指针如果要在config_destroy()

之后使用需要复制到另一个数组中

全局结构内存错误

Global struct memory error

c

struct

heap-memory

valgrind

libconfig