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c++cstringdebugginggdb
John Carter
John Carter

Reputation: 55369

How do I print the full value of a long string in gdb?

I want to print the full length of a C-string in GDB. By default it's being abbreviated, how do I force GDB to print the whole string?

Upvotes: 470

Views: 293960

Answers (6)

John Carter
John Carter

Reputation: 55369

set print elements 0

From the GDB manual:

set print elements number-of-elements
Set a limit on how many elements of an array GDB will print. If GDB is printing a large array, it stops printing after it has printed the number of elements set by the set print elements command. This limit also applies to the display of strings. When GDB starts, this limit is set to 200. Setting number-of-elements to zero means that the printing is unlimited.

Upvotes: 636

korry
korry

Reputation: 886

The printf command will print the complete strings:

(gdb) printf "%s\n", string

Upvotes: 62

mrtimdog
mrtimdog

Reputation: 497

Using set elements ... isn't always the best way. It would be useful if there were a distinct set string-elements ....

So, I use these functions in my .gdbinit:

define pstr
  ptype $arg0._M_dataplus._M_p
  printf "[%d] = %s\n", $arg0._M_string_length, $arg0._M_dataplus._M_p
end

define pcstr
  ptype $arg0
  printf "[%d] = %s\n", strlen($arg0), $arg0
end

Caveats:

  • The first is c++ lib dependent as it accesses members of std::string, but is easily adjusted.
  • The second can only be used on a running program as it calls strlen.

Upvotes: 2

abstraktor
abstraktor

Reputation: 1045

Just to complete it:

(gdb) p (char[10]) *($ebx)
$87 =   "asdfasdfe\n"

You must give a length, but may change the representation of that string:

(gdb) p/x (char[10]) *($ebx)
$90 =   {0x61,
  0x73,
  0x64,
  0x66,
  0x61,
  0x73,
  0x64,
  0x66,
  0x65,
  0xa}

This may be useful if you want to debug by their values

Upvotes: 25

Wichert Akkerman
Wichert Akkerman

Reputation: 5348

There is a third option: the x command, which allows you to set a different limit for the specific command instead of changing a global setting. To print the first 300 characters of a string you can use x/300s your_string. The output might be a bit harder to read. For example printing a SQL query results in:

(gdb) x/300sb stmt.c_str()
0x9cd948:    "SELECT article.r"...
0x9cd958:    "owid FROM articl"...
..

Upvotes: 45

user149341
user149341

Reputation:

As long as your program's in a sane state, you can also call (void)puts(your_string) to print it to stdout. Same principle applies to all functions available to the debugger, actually.

Upvotes: 121

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