如何在保留ascii形式的ascii字符的同时，使gdb以十六进制而不是八进制打印字符串的不可打印字符? [英] How can I make gdb print unprintable characters of a string in hex instead of octal while preserving the ascii characters in ascii form?

问题描述

假设我有一个缓冲区buf，其c字符串表示为

Suppose I have a buffer buf whose c string representation is

 char* buf = "Hello World \x1c"

当我使用命令p buf在gdb中打印此buf时，得到以下内容

When I print this buf in gdb using the command p buf, I get the following

 $1 = "Hello World \034"

是否有打印命令或gdb设置将代替打印以下内容?

$1 = "Hello World \x1c"

我尝试了各种格式参数，例如/c和/x，但是它们都没有达到我想要的效果.我也玩过printf，但无法达到预期的效果.

I have tried various format parameters such as /c and /x, but none of them get the effect that I am looking for. I have also played with printf but was unable to achieve the desired effect.

更新:我正在使用"GNU gdb(GDB)7.0.1-debian".

Update: I am using "GNU gdb (GDB) 7.0.1-debian".

更新: 我也玩过x.

Update: I have played with x as well.

如果我执行x/c，它将打印八进制和十进制的不可打印字符，然后打印带有ascii和十进制的可打印字符.

If I do x/c it prints octal and decimal for nonprintable characters, and then prints printable characters with the ascii and decimal.

如果执行x/s，则其输出与p命令完全相同.

If I do x/s it outputs exactly the same as the p command.

如果我执行x/x，它只会输出十六进制，但是我们会丢失可打印部分的ASCII字符.

If I do x/x it just outputs hex but then we lose the ascii characters for the printable part.

更新:此参考除非不完整，否则表明我希望无法使用，但是任何人都可以确认吗?

Update: This reference, unless incomplete, suggests that what I desire is not available, but can anyone confirm?

推荐答案

在没有现有解决方案的情况下，我创建了此gdb命令会为混合了可打印的ascii和不可打印的字符的字符串打印ascii和hex.来源转载如下.

In the absence of an existing solution, I created this gdb command which prints ascii and hex for strings that have mixed printable ascii and non-printable characters. The source is reproduced below.

from __future__ import print_function

import gdb
import string
class PrettyPrintString (gdb.Command):
    "Command to print strings with a mix of ascii and hex."

    def __init__(self):
        super (PrettyPrintString, self).__init__("ascii-print",
                gdb.COMMAND_DATA,
                gdb.COMPLETE_EXPRESSION, True)
        gdb.execute("alias -a pp = ascii-print", True)

    def invoke(self, arg, from_tty):
        arg = arg.strip()
        if arg == "":
            print("Argument required (starting display address).")
            return
        startingAddress = gdb.parse_and_eval(arg)
        p = 0
        print('"', end='')
        while startingAddress[p] != ord("\0"):
            charCode = int(startingAddress[p].cast(gdb.lookup_type("char")))
            if chr(charCode) in string.printable:
                print("%c" % chr(charCode), end='')
            else:
                print("\\x%x" % charCode, end='')
            p += 1
        print('"')

PrettyPrintString()

要使用此功能，只需将source AsciiPrintCommand.py放入，然后在gdb中运行以下命令即可.为方便起见，可以将上述源代码命令放入其$HOME/.gdbinit.

To use this, one can simply put the source AsciiPrintCommand.py and then run the following in gdb. For convenience, one can put put the above source command into their $HOME/.gdbinit.

ascii-print buf
"Hello World \x1c"

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