backtrace-d

backtrace-d is a library that provides a pretty backtrace for D applications running under Linux. Its usage is very simple, you'll only need to import the module backtrace.backtrace and call printPrettyTrace. Also, make sure that you compile with debug symbols on. On DMD, for example, use the -g flag.

backtrace-d was tested using DMD 2.063.2 and LDC2 0.12.0.

You can also try the experimental install call to make backtraces showing on exceptions beautiful. This works using DMD compiled applications only for now.

Example on using printPrettyTrace

import backtrace;
import std.stdio;

void main() {
  goToF1();
}

void goToF1() {
  goToF2();
}

void goToF2(uint i = 0) {
  if (i == 2) {
    printPrettyTrace(stderr); return;
  }
  goToF2(++i);
}

This will print the following to the standard error:

Stack trace:
#1: /path/to/source/app.d line (14) in void app.goToF2(uint)

 (11)
 (12)     void goToF2(uint i = 0) {
 (13)       if (i == 2) {
>(14)         printPrettyTrace(stderr); return;
 (15)       }
 (16)       goToF2(++i);
 (17)     }

#2: /path/to/source/app.d line (17) in void app.goToF2(uint)

 (14)         printPrettyTrace(stderr); return;
 (15)       }
 (16)       goToF2(++i);
>(17)     }

#3: /path/to/source/app.d line (17) in void app.goToF2(uint)
#4: /path/to/source/app.d line (10) in void app.goToF1()
#5: /path/to/source/app.d line (5) in _Dmain

Example on using install (DMD only)

static import backtrace;
import std.stdio;

void main() {
  backtrace.install(stderr);

  goToF1();
}

void goToF1() {
  goToF2();
}

void goToF2(uint i = 0) {
  if (i == 2) throw new Exception("Exception thrown");
  goToF2(++i);
}

This will print the following to the standard error:

object.Exception@source/app.d(15): Exception thrown
----------------
Stack trace:
#1: /path/to/source/app.d line (16) in void app.goToF2(uint)

 (13)
 (14) void goToF2(uint i = 0) {
 (15)   if (i == 2) throw new Exception("Exception thrown");
>(16)   goToF2(++i);
 (17) }

#2: /path/to/source/app.d line (17) in void app.goToF2(uint)

 (14) void goToF2(uint i = 0) {
 (15)   if (i == 2) throw new Exception("Exception thrown");
 (16)   goToF2(++i);
>(17) }

#3: /path/to/source/app.d line (17) in void app.goToF2(uint)
#4: /path/to/source/app.d line (12) in void app.goToF1()
#5: /path/to/source/app.d line (7) in _Dmain
----------------

You can customize the way the backtrace is printed using the following options:

PrintOptions options;
options.detailedForN = 2;        //number of frames to show code for
options.numberOfLinesBefore = 3; //number of lines of code to show before the specific line
options.numberOfLinesAfter  = 3; //number of lines of code to show after the specific line
options.colored = true;          //enable colored output for the backtrace
options.stopAtDMain = false;     //show stack traces after the entry point of the D code
printPrettyTrace(stdout, options);

Documentation

//prints the backtrace to `output` using the printing `options` provided. Frames to skip is used to
//skip frames that belong to the internal code of the library. You might need to change this depending
//on the optimization level of your compiler
void printPrettyTrace(File output, PrintOptions options = PrintOptions.init, uint framesToSkip = 1)

//install the runtime trace handler to print the backtraces
void install(File file, PrintOptions options = PrintOptions.init, uint framesToSkip = 6)

//returns an array of backtrace addresses
void*[] getBacktrace()

//returns an array of symbols provided an array of addresses
Symbol[] getBacktraceSymbols(const(void*[]) backtrace)

//returns an array of lines and files corresponding to the addresses provided
//this uses `addr2line` tool internally
Trace[] getLineTrace(const(void*[]) backtrace)

Work to do and bugs

• Inaccurate address to line resolving.

• Problem could reside in the debug symbols emitted by the compilers or the code that produces backtrace addresses.

• Integrate the library with Runtime.traceHandler (work in progress)

• Only works under DMD for now.

Feedback and pull requests

Please use Github's issue tracker. I'm also open to pull and feature requests.