我正在调试一个网络代码,并想要打印已声明为
如何以有意义的格式打印它们?
int32
的IP地址。当使用gdb print命令打印时,我得到了一些不太有意义的值。如何以有意义的格式打印它们?
int32
的IP地址。当使用gdb print命令打印时,我得到了一些不太有意义的值。只需使用inet_ntoa(3)
即可:
(gdb) p (char*)inet_ntoa(0x01234567) # Replace with your IP address
$1 = 0xa000b660 "103.69.35.1"
然而inet_ntoa()函数并不接受u_int32_t参数,而是一个struct in_addr参数,因此先前的答案:
p (char *)inet_ntoa(3)
对我来说似乎是错误的。
以下是一种在名为gdb.cmd.txt的文件中定义函数的方法,因此在启动时调用"gdb -x gdb.cmd.txt"。
在gdb.cmd.txt中,输入以下内容:
define ntoa
set $ipv4 = $arg0
echo IPV4 =.
p $ipv4
set $val1 = ($ipv4 >> 24) & 0xff
set $val2 = ($ipv4 >> 16) & 0xff
set $val3 = ($ipv4 >> 8) & 0xff
set $val4 = ($ipv4 >> 0) & 0xff
printf "IPV4=%u=0x%02x.%02x.%02x.%02x =%d.%d.%d.%d\n", $ipv4, $val1, $val2, $val3, $val4, $val1, $val2, $val3, $val4
end
(gdb) ntoa(0x01020304)
IPV4 =.$10 = 16909060
IPV4=16909060=0x01.02.03.04 =1.2.3.4
(gdb) ntoa(-1)
IPV4 =.$10 = -1
IPV4=4294967295=0xff.ff.ff.ff =255.255.255.255
顺便说一下:我现在正在搜索是否有方法可以在gdb中让函数返回格式化的字符串,这样我就可以运行命令“p ntoa(0x01020304)”或“p ntoa(ptr->ipv4_addresss)”(假设ptr是包含u_int32_t ipv4_address数据元素的结构体的有效指针)。但似乎gdb用户定义的函数不允许使用sprintf()调用。
-丹尼斯·贝德纳尔,2012年12月
(gdb) p/uc (char[4]) 342757386
$4 = {10 '\n', 16 '\020', 110 'n', 20 '\024'}
p/uc
: 告诉gdb将数据视为无符号字符内容。
(char[4]) 342757386
: 将IP转换为由4个char元素组成的数组,每个元素表示一个字节/八位字节。
因此,您告诉gdb将IP的十进制表示视为四个字节的数组 - 四个八位字节 - 然后将它们打印为无符号字符。
如果您忽略每个字节的ASCII表示,则可以得到您的IP地址:10.16.110.20
。
尝试使用此命令:
(gdb) p/uc (char[4])342757386
$1 = {10 '\n', 16 '\020', 110 'n', 20 '\024'}
这里有另一种有趣的方法:
#include <sys/types.h> // u_int32_t
// next 3 for inet_ntoa() call
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
// C++ headers
#include <iostream> // std::cout
#include <string>
#include <sstream> // ostringstream
// class to aid in using the gdb(3) debugger to print a u_int32_t ip_address as a string.
// The toString() is a static method!!
// How to call a C++ method from the gdb debugger, to simulate the inet_nto(3) method
//
// From within gdb debugger, you must have a process, so first stop at main:
// b main
// r
//
// (gdb) p MYIP4::toString(0x0fffefdfc)
// $1 = "255.254.253.252"
//
// (gdb) p MYIP4::toString(-1)
// $2 = "255.255.255.255"
//
// (gdb) p MYIP4::toString(65536)
// $3 = "0.1.0.0"
//
// Drawbacks: the a.out executable that you are debugging needs the MYIP4 class already
// compiled and linked into the executable that you are debugging.
//
// PS: I don't know if there is a "slick way" where the MyIP4 class could dynamically be loaded,
// within gdb(), if the executable failed to contain the MYIP4 class.
//
// PS: I had trouble with my operator() idea.. If you know how to improve on it, post away!
//
// @author 1201207 dpb created
//=============================
class MYIP4
{
public:
static std::string toString(u_int32_t ipv4_address )
{
struct in_addr temp_addr;
// inet_ntoa() returns a char * to a buffer which may be overwritten
// soon, so convert char* to a string for extra safety.
temp_addr.s_addr = htonl(ipv4_address);
std::string ipv4String = std::string(inet_ntoa( temp_addr ));
return ipv4String;
}
#if 0
// this idea did NOT work, so it is commented out.
//
// overload the () operator, so that, within gdb, we can simply type:
// p MYIP4(0x01020304)
// instead of:
// p MYIP4::toString(0x01020304)
std::string operator() ( u_int32_t ipv4_address )
{
return toString(ipv4_address);
}
#endif
};
void test1();
int main()
{
test1();
return 0;
}
void test1()
{
u_int32_t ipv4Address = 0x01020304; // host byte order for 1.2.3.4
std::cout << "Test1: IPAddress=" << MYIP4::toString(ipv4Address) << "\n";
}
malloc
函数分配内存,例如:(gdb) p (void*)malloc(64); $1 = (void *) 0x12345678; (gdb) p (char*)inet_ntop(23,&my_ip6_addr,0x12345678,64)
。 - Adam Rosenfield