sprintf问题 [英] sprintf problem
问题描述
您好，我想以十六进制格式显示指针指向的地址
，就像我的调试器显示它一样。
说我有P * ptr;其中P是某种类型。
我试过：
std :: sprintf（message，"％＃0x，（unsigned int）ptr）;
但是这给了我：0xFFFF例如，当我想要0x0000FFFF时，即，我不要/ b $ b想要丢弃任何前导零。我知道这只是一个小小的化妆品问题，但我仍然想知道如何做到这一点。
感谢您的回复！
/ WP
Hello, I want to display the address a pointer points to in hexadecimal form
in the same way my debugger displays it.
Say I have P* ptr; where P is some type.
I tried:
std::sprintf(message, "%#0x, (unsigned int)ptr);
But that gives me: 0xFFFF for example, when I want 0x0000FFFF, i.e., I dont
want to drop any leading zeros. I know this is just a small cosmetic
problem, but I still would like to know how to accomplish this.
Thanks for any replies!
/ WP
推荐答案
" William Payne" < MI ************** @ student.liu.se>在留言中写道
news：ci ********** @ news.island.liu.se ...
"William Payne" <mi**************@student.liu.se> wrote in message
news:ci**********@news.island.liu.se...
你好，我想要显示将指针指向十六进制
形式，就像我的调试器显示它一样。
说我有P * ptr;其中P是某种类型。
我试过：
std :: sprintf（消息，"％＃0x，（unsigned int）ptr）;
但是这给了我：0xFFFF例如，当我想要0x0000FFFF时，即I
不想丢弃任何前导零。我知道这只是一个小的化妆品问题，但我仍然想知道如何做到这一点。
感谢您的回复！
Hello, I want to display the address a pointer points to in hexadecimal form in the same way my debugger displays it.
Say I have P* ptr; where P is some type.
I tried:
std::sprintf(message, "%#0x, (unsigned int)ptr);
But that gives me: 0xFFFF for example, when I want 0x0000FFFF, i.e., I dont want to drop any leading zeros. I know this is just a small cosmetic
problem, but I still would like to know how to accomplish this.
Thanks for any replies!
#include< stdio.h>
#define char_count（sizeof（unsigned int）* 2）
int main（）
{
unsigned int i = 0;
int * ptr =& i;
char message [2 * sizeof * ptr] = {0};
sprintf（message，"％0 * x"，2 * sizeof ptr，（unsigned int）ptr）;
put（留言）;
返回0;
}
备注：
将指向unsigned int的指针的结果定义为实现。
指示指针的格式说明符是％p。
使用％p说明符生成的文本格式是实现
定义。
类型的大小' 'unsigned int''不一定是四个字节（但必须是
至少两个字节）。
一个字节的大小不一定是8位（但必须是
至少8位）。
IOW：上面的代码不便携。
-Mike
#include <stdio.h>
#define char_count (sizeof (unsigned int) * 2)
int main()
{
unsigned int i = 0;
int *ptr = &i;
char message[2 * sizeof *ptr] = {0};
sprintf(message, "%0*x", 2 * sizeof ptr, (unsigned int)ptr);
puts(message);
return 0;
}
Notes:
The result of casting a pointer to unsigned int is implementation defined.
The format specifier indicating a pointer is %p.
The format of the text produced with the %p specifier is implementation
defined.
The size of type ''unsigned int'' is not necessarily four bytes (but must be
at least two bytes).
The size of a byte is not necessarily eight bits (but must be at
least eight bits).
IOW: the above code is not portable.
-Mike
" Mike Wahler < MK ****** @ mkwahler.net>在消息中写道
新闻：Eh ************** @ newsread1.news.pas.earthlink .net ...
"Mike Wahler" <mk******@mkwahler.net> wrote in message
news:Eh**************@newsread1.news.pas.earthlink .net...
＃ include< stdio.h>
#define char_count（sizeof（unsigned int）* 2）
#include <stdio.h>
#define char_count (sizeof (unsigned int) * 2)
不使用此宏。只是一个'心理记录''
我忘了扔掉。 :-)
-Mike
This macro is not used. Just a ''mental note''
I forgot to throw away. :-)
-Mike
" Mike Wahler" < MK ****** @ mkwahler.net>在消息中写道
news：am *************** @ newsread1.news.pas.earthlin k.net ...
"Mike Wahler" <mk******@mkwahler.net> wrote in message
news:am***************@newsread1.news.pas.earthlin k.net...
Mike Wahler < MK ****** @ mkwahler.net>在消息中写道
新闻：Eh ************** @ newsread1.news.pas.earthlink .net ...
"Mike Wahler" <mk******@mkwahler.net> wrote in message
news:Eh**************@newsread1.news.pas.earthlink .net...
使用C ++ IOStreams：
#include< iomanip>
#include< ios>
#include< ; iostream>
#include< sstream>
int main（）
{
int i = 0;
int * ptr =& i;
std :: ostringstream oss;
oss< < std :: hex
<< std :: setfill（''0''）
<< std :: setw（2 * sizeof * ptr）
<< ptr
<< ''\ n'';
std :: cout<< oss.str（）。c_str（）<< ''\ n'';
返回0;
}
-Mike
Using C++ IOStreams:
#include <iomanip>
#include <ios>
#include <iostream>
#include <sstream>
int main()
{
int i = 0;
int *ptr = &i;
std::ostringstream oss;
oss << std::hex
<< std::setfill(''0'')
<< std::setw(2* sizeof *ptr)
<< ptr
<< ''\n'';
std::cout << oss.str().c_str() << ''\n'';
return 0;
}
-Mike
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