linux – strftime_l lib64 / libc.so.6中的SIGSEGV分段错误

发布时间：2020-12-14 00:52:11 所属栏目：Linux 来源：网络整理

导读：我将pro * c代码从UNIX移植到LINUX.代码被成功编译和创建可执行文件.但在运行时它的提升分段错误.我一步一步地调试了代码,下面是GDB调试的输出. Breakpoint 4 at 0x3b19690f50 (gdb) n 525 strftime (buf,MAX_STRING_LEN,"%d/%b/%Y:%H:%M:%S",dummy_time); (

我将pro * c代码从UNIX移植到LINUX.代码被成功编译和创建可执行文件.但在运行时它的提升分段错误.我一步一步地调试了代码,下面是GDB调试的输出.

Breakpoint 4 at 0x3b19690f50
 (gdb) n
 525             strftime (buf,MAX_STRING_LEN,"%d/%b/%Y:%H:%M:%S",dummy_time);
 (gdb) n

 Breakpoint 4,0x0000003b19690f50 in strftime () from /lib64/libc.so.6
 (gdb) n
 Single stepping until exit from function strftime,which has no line number information.
 0x0000003b19690f70 in strftime_l () from /lib64/libc.so.6
 (gdb) n
 Single stepping until exit from function strftime_l,which has no line number information.

 Program received signal SIGSEGV,Segmentation fault.
 0x0000003b19690f8b in strftime_l () from /lib64/libc.so.6

实际上在代码中调用函数strftime().但我不知道为什么它会在/lib64/libc.so.6中到达strftime_l().

这个问题不会出现在UNIX中.请帮忙.代码是

static void speed_hack_libs(void)
{
    time_t dummy_time_t = time(NULL);
    struct tm *dummy_time = localtime (&dummy_time_t);
    struct tm *other_dummy_time = gmtime (&dummy_time_t);
    char buf[MAX_STRING_LEN];
    strftime (buf,dummy_time);
}

解决方法

struct tm *dummy_time = localtime (&dummy_time_t);
struct tm *other_dummy_time = gmtime (&dummy_time_t);

这不会奏效.从man page：

The localtime() function converts the calendar time timep to broken-down time representation,expressed relative to the user’s specified time-zone. … The return value points to a statically allocated struct which might be overwritten by
subsequent calls to any of the date and time functions.

The gmtime() function converts the calendar time timep to broken-down time representation,expressed in Coordinated Universal Time (UTC). It
may return NULL when the year does not fit into an integer. The return value points to a statically allocated struct which might be overwritten by subsequent calls to any of the date and time functions.

因此,* dummy_time可能会在您使用它时被覆盖,并包含不可预测的垃圾.您应该将数据复制到缓冲区,如下所示：

struct tm dummy_time ;
memcpy(&dummy_time,localtime (&dummy_time_t),sizeof(struct tm));

虽然我不确定这怎么会导致SIGSEGV(可能是获得月份名称等等 – 检查问题是否仍然存在于LC_ALL = C),你必须先解决这个问题才能继续.另外,检查(在调试器中)* dummy_time的内容.

（编辑：李大同）

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