mongoc_debugging - Man Page

Aids for Debugging


This repository contains a .gdbinit file that contains helper functions to aid debugging of data structures. GDB will load this file automatically if you have added the directory which contains the .gdbinit file to GDB's auto-load safe-path, and you start GDB from the directory which holds the .gdbinit file.

You can see the safe-path with show auto-load safe-path on a GDB prompt. You can configure it by setting it in ~/.gdbinit with:

add-auto-load-safe-path /path/to/mongo-c-driver

If you haven't added the path to your auto-load safe-path, or start GDB in another directory, load the file with:

source path/to/mongo-c-driver/.gdbinit

The .gdbinit file defines the printbson function, which shows the contents of a bson_t * variable. If you have a local bson_t, then you must prefix the variable with a &.

An example GDB session looks like:

(gdb) printbson bson
ALLOC [0x555556cd7310 + 0] (len=475)
    'bool' : true,
    'int32' : NumberInt("42"),
    'int64' : NumberLong("3000000042"),
    'string' : "Stŕìñg",
    'objectId' : ObjectID("5A1442F3122D331C3C6757E1"),
    'utcDateTime' : UTCDateTime(1511277299031),
    'arrayOfInts' : [
        '0' : NumberInt("1"),
        '1' : NumberInt("2")
    'embeddedDocument' : {
        'arrayOfStrings' : [
            '0' : "one",
            '1' : "two"
        'double' : 2.718280,
        'notherDoc' : {
            'true' : NumberInt("1"),
            'false' : false
    'binary' : Binary("02", "3031343532333637"),
    'regex' : Regex("@[a-z]+@", "im"),
    'null' : null,
    'js' : JavaScript("print foo"),
    'jsws' : JavaScript("print foo") with scope: {
        'f' : NumberInt("42"),
        'a' : [
            '0' : 3.141593,
            '1' : 2.718282
    'timestamp' : Timestamp(4294967295, 4294967295),
    'double' : 3.141593


The mongo-c-driver repository contains a script that can be imported into an LLDB sessions and allows rich inspection of BSON values.


The module requires an LLDB with Python 3.8 or newer.

To activate the script, import it from the LLDB command line:

(lldb) command script import /path/to/mongo-c-driver/

Upon success, the message lldb_bson is ready will be printed to the LLDB console.

The import of this script can be made automatic by adding the command to an .lldbinit file. For example: Create a file ~/.lldbinit containing:

command script import /path/to/mongo-c-driver/

The docstring at the top of the file contains more information on the capabilities of the module.

Debug Assertions

To enable runtime debug assertions, configure with -DENABLE_DEBUG_ASSERTIONS=ON.


MongoDB, Inc


Sep 06, 2023 1.24.4 libmongoc