Back

Backtraces for Odin on the major platforms (MacOS, Linux, Windows).

For Windows support, all credit goes to DaseinPhaos/pdb.

NOTE: The pdb package allocates a lot of stuff and does not really provide a way of deleting the allocations, so, before calling into the package, this package sets it to use the context.temporary_allocator.

In debug mode, the back.lines will try to use the debug information to get source files and line numbers. When not in debug mode, you will get greatly reduced information.

Installation

Back does not use any libraries or external dependencies not pre-installed on the OS.

On Linux, the addr2line command is invoked, which comes pre-installed (maybe in binutils).

The addr2line command can be changed by setting the -define:BACK_ADDR2LINE_PATH=your/atos flag.

The path to the running binary is also needed for this command, this is os.args[0] by default and to my knowledge is always correct. Nevertheless it can be changed with the -define:BACK_PROGRAM=path/to/binary flag.

To change the size (amount of stackframes to print) in places where this can't be set directly, you can use the -define:BACKTRACE_SIZE=16.

Manual

package manual

import "core:fmt"

import back "../.."

main :: proc() {
	// Allocates for 16 frames.
	bt := back.trace_n(16)
	print(bt)

	// Or, doesn't allocate, returns `-define:BACKTRACE_SIZE` frames.
	btc := back.trace()
	print(btc.trace[:btc.len])

	// Or, fill in a slice.
	bt = make(back.Trace, 16)
	bt = bt[:back.trace_fill(bt)]
	print(bt)
}

print :: proc(bt: back.Trace) {
	lines, err := back.lines(bt)
	if err != nil {
		fmt.eprintf("Could not retrieve backtrace lines: %v\n", err)
	} else {
		defer back.lines_destroy(lines)

		fmt.eprintln("[back trace]")
		back.print(lines)
	}
}

// [back trace]
//     back.trace_n - /Users/laytan/projects/back/back.odin:59
//     manual.main  - /Users/laytan/projects/back/examples/manual/main.odin:9
//     main         - /Users/laytan/third-party/Odin/core/runtime/entry_unix.odin:53
// [back trace]
//     back.trace  - /Users/laytan/projects/back/back.odin:52
//     manual.main - /Users/laytan/projects/back/examples/manual/main.odin:13
//     main        - /Users/laytan/third-party/Odin/core/runtime/entry_unix.odin:53
// [back trace]
//     back.trace_fill - /Users/laytan/projects/back/back.odin:64
//     manual.main     - /Users/laytan/projects/back/examples/manual/main.odin:18
//     main            - /Users/laytan/third-party/Odin/core/runtime/entry_unix.odin:53

Tracking Allocator

package main

import "back"

_main :: proc() {
	_ = new(int)
	free(rawptr(uintptr(100)))
}

main :: proc() {
	track: back.Tracking_Allocator
	back.tracking_allocator_init(&track, context.allocator)
	defer back.tracking_allocator_destroy(&track)

	context.allocator = back.tracking_allocator(&track)
	defer back.tracking_allocator_print_results(&track)

	_main()
}

// /Users/laytan/projects/back/examples/allocator/main.odin(6:6) leaked 8b
// [back trace]
//     back.trace                   - /Users/laytan/projects/back/back.odin:52
//     back.tracking_allocator_proc - /Users/laytan/projects/back/allocator.odin:129
//     runtime.mem_alloc_bytes      - /Users/laytan/third-party/Odin/core/runtime/internal.odin:141
//     runtime.new_aligned-13136    - /Users/laytan/third-party/Odin/core/runtime/core_builtin.odin:250
//     runtime.new-13097            - /Users/laytan/third-party/Odin/core/runtime/core_builtin.odin:246
//     main._main                   - /Users/laytan/projects/back/examples/allocator/main.odin:6
//     main.main                    - /Users/laytan/projects/back/examples/allocator/main.odin:18
//     main                         - /Users/laytan/third-party/Odin/core/runtime/entry_unix.odin:53
//
//
// /Users/laytan/projects/back/examples/allocator/main.odin(7:2) allocation 64 was freed badly
// [back trace]
//     back.trace                   - /Users/laytan/projects/back/back.odin:52
//     back.tracking_allocator_proc - /Users/laytan/projects/back/allocator.odin:102
//     runtime.mem_free             - /Users/laytan/third-party/Odin/core/runtime/internal.odin:162
//     main._main                   - /Users/laytan/projects/back/examples/allocator/main.odin:8
//     main.main                    - /Users/laytan/projects/back/examples/allocator/main.odin:18
//     main                         - /Users/laytan/third-party/Odin/core/runtime/entry_unix.odin:53

Printing a backtrace on assertion failures / panics

package main

import "back"

main :: proc() {
    context.assertion_failure_proc = back.assertion_failure_proc
    assert(3 == 2)
}

// [back trace]
//     back.trace                  - /Users/laytan/projects/back/back.odin:52
//     back.assertion_failure_proc - /Users/laytan/projects/back/back.odin:97
//     runtime.assert.internal-0   - /Users/laytan/third-party/Odin/core/runtime/core_builtin.odin:818
//     runtime.assert              - /Users/laytan/third-party/Odin/core/runtime/core_builtin.odin:820
//     main.main                   - /Users/laytan/projects/back/examples/assert_backtrace/main.odin:8
//     main                        - /Users/laytan/third-party/Odin/core/runtime/entry_unix.odin:53
// /Users/laytan/projects/back/examples/assert_backtrace/main.odin(7:5) runtime assertion

Printing a backtrace on segmentation faults

package main

import "back"

main :: proc() {
	back.register_segfault_handler()

	ptr: ^int
	bad := ptr^ + 2
	_ = bad
}

// Segmentation Fault
// [back trace]
//     back.trace                            - /Users/laytan/projects/back/back.odin:52
//     back.register_segfault_handler$anon-1 - /Users/laytan/projects/back/back.odin:114
//     ??                                    - ??
//     main.main                             - /Users/laytan/projects/back/examples/segfault/main.odin:8