当我尝试打印可变长度字符串时,我遇到了分段错误。当我使用printf或日志文件打印字符串时,字符串被打印得很好。另一个问题是,我只在一些机器上看到崩溃,因为相同的测试在另一台机器上工作正常。我真的很困惑为什么。
编辑:一个完整的工作代码导致我在下面粘贴的崩溃。 崩溃是Centos 6.3和Centos 6.5。在Centos 5中没有出现崩溃
#include <stdio.h>
#include <stdarg.h>
#include <stdint.h>
#include <sys/time.h>
#include <time.h>
typedef struct {
uint64_t total_bytes_sent;
uint64_t total_bytes_received;
uint64_t total_blocks_sent;
uint64_t total_blocks_received;
uint64_t total_commands_sent;
uint64_t total_commands_received;
uint64_t time_to_process_data;
char mark_sent_time[64];
char mark_received_time[64];
} csperf_stats_t;
void
csperf_stats_printf(const char *format, ...)
{
/* Write to file */
va_list args;
/* Write to stdout */
va_start(args, format);
vfprintf(stdout, format, args);
va_end(args);
}
void
ansperf_stats_display(csperf_stats_t *stats)
{
if (!stats) {
return;
}
stats->total_blocks_sent = 1000;
stats->total_blocks_received = 2000;
stats->time_to_process_data = 22;
csperf_stats_printf("%3d %15s %10s %10zu %10zu %10zu %10s "
"%10s\n\n",
0, "hi", "testing.",
stats->total_blocks_sent, stats->total_blocks_received,
stats->time_to_process_data,
"crash", "test");
}
/* Get time in millisecond */
uint64_t
csperf_network_get_time(char *buf)
{
char fmt[64];
struct tm *tm;
struct timeval tv;
uint64_t s;
gettimeofday(&tv, NULL);
if (buf) {
if((tm = localtime(&tv.tv_sec)) != NULL) {
strftime(fmt, sizeof(fmt), "%Y-%m-%d %H:%M:%S.%03u", tm);
snprintf(buf, sizeof(fmt), fmt, tv.tv_usec);
}
}
s = tv.tv_sec * 1000LL;
return(s + tv.tv_usec / 1000LL);
}
int main()
{
csperf_stats_t stats = { 0 };
csperf_network_get_time(stats.mark_sent_time);
csperf_network_get_time(stats.mark_received_time);
printf("%s%s\n", stats.mark_sent_time, stats.mark_received_time);
ansperf_stats_display(&stats);
}
以下是崩溃的代码段。
当它试图打印stats-&gt; mark_sent_time,stats-&gt; mark_received_time时,它在vfprintf()中崩溃。当我在gdb中打印字符串时,它并没有抱怨。
void
csperf_stats_printf(FILE *fd, const char *format, ...)
{
/* Write to file */
va_list args;
va_start(args, format);
if (fd) {
vfprintf(fd, format, args);
}
va_end(args);
/* Write to stdout */
va_start(args, format);
vfprintf(stdout, format, args);
va_end(args);
}
void
ansperf_stats_display(csperf_stats_t *stats, FILE *fd)
{
static int header_displayed = 0;
static int cycle = 0;
char total_bytes_sent_str[50];
char total_bytes_recv_str[50];
if (!stats) {
return;
}
if (!header_displayed) {
csperf_stats_printf(fd, "%s%s", header, seperator_line);
header_displayed = 1;
}
csperf_common_calculate_size(total_bytes_sent_str,
stats->total_bytes_sent);
csperf_common_calculate_size(total_bytes_recv_str,
stats->total_bytes_received);
csperf_stats_printf(fd, "%3d %15s %10s %10zu %10zu %10zu %10s "
"%10s\n\n", ++cycle,
total_bytes_sent_str, total_bytes_recv_str,
stats->total_blocks_sent, stats->total_blocks_received,
stats->time_to_process_data,
stats->mark_sent_time, stats->mark_received_time);
}
这就是gdb显示的内容
(gdb) p stats->mark_sent_time
No symbol "stats" in current context.
(gdb) f 2
#2 0x08051f56 in ansperf_stats_display (stats=0x892ded4, fd=0x892e888) at /home/nikhil/csperf/src/csperf_stats.c:55
55 csperf_stats_printf(fd, "%3d %15s %10s %10zu %10zu %10zu %100s "
(gdb) p stats->mark_sent_time
$1 = "20160821 21325800007", '\000' <repeats 79 times>
(gdb) p stats->mark_recei9ved_time
There is no member named mark_recei9ved_time.
(gdb) p stats->mark_received_time
$2 = "20160821 21325800007", '\000' <repeats 79 times>
字符串是一个100字节的数组,如下所示
char mark_sent_time[100];
char mark_received_time[100];
设置如下:
command->echo_timestamp = csperf_network_get_time(
client->stats.mark_sent_time);
此函数将时间戳复制到字符串&#34; mark_sent_time&#34;
uint64_t
csperf_network_get_time(char *buf)
{
char fmt[64];
struct tm *tm;
struct timeval tv;
uint64_t s;
gettimeofday(&tv, NULL);
if (buf) {
if((tm = localtime(&tv.tv_sec)) != NULL) {
strftime(fmt, sizeof(fmt), "%Y-%m-%d %H:%M:%S.%03u", tm);
snprintf(buf, sizeof(fmt), fmt, tv.tv_usec);
}
}
s = tv.tv_sec * 1000LL;
return(s + tv.tv_usec / 1000LL);
}
回溯:
(gdb) bt
#0 0x002b535e in _IO_vfprintf_internal (s=Cannot access memory at address 0xffffffff
) at vfprintf.c:1603
#1 0x08051de7 in csperf_stats_printf (fd=0x892e888, format=0x8079a6c "%3d %15s %10s %10zu %10zu %10zu %100s %100s \n\n") at /home/nikhil/csperf/src/csperf_stats.c:23
#2 0x08051f56 in ansperf_stats_display (stats=0x892ded4, fd=0x892e888) at /home/nikhil/csperf/src/csperf_stats.c:55
#3 0x08050ad3 in csperf_client_shutdown (client=0x892deb0) at /home/nikhil/csperf/src/csperf_client.c:67
我错过了什么?
答案 0 :(得分:2)
问题是您使用%zu
在格式字符串中显示uint64_t
变量。
在64位目标上,%zu
适用于size_t
,并且(至少在我的64位系统上)这是64位。然而,在32位系统上(至少对我而言)size_t
是32位,但uint64_t
变量仍将64位置于va_list
结构中。 %zu
仅消耗32位,这会在va_list
中留下32位值,而不是下一个参数。
在打印uint64_t变量时,将"%zu"
的使用替换为"%" PRIu64
(在您的示例中至少有3个位置)。
您可能需要添加<inttypes.h>
标头才能访问PRIu64
。
....正如我在评论中提到的,我不认为这个:
strftime(fmt, sizeof(fmt), "%Y-%m-%d %H:%M:%S.%03u", tm);
snprintf(buf, sizeof(fmt), fmt, tv.tv_usec);
正在做你期望的事。我认为您可能希望%03u
行中的strftime
延伸到snprintf
行以使用tv.tv_usec
,但是%u
用于strftime
我是星期几作为数字,您可能应该在%%03u
来电中使用strftime
,然后fmt
snprintf
只包含%03u