Exception Hierarchy [WAS: Re: Top 5]

[Frits van Bommel]

Brad Roberts wrote:
> For anything running on top of glibc (ie, every linux distribution) it's 
> fairly trivial via backtrace() and backtrace_symbols() found in 
> execinfo.h.  The symbols are the mangled form, but that's a simple matter 
> of code to translate back to more meaningful names.  An incomplete version 
> of that is available in phobos already (and probably somewhere in Tango 
> too) -- and it should really be in the core runtime, probably.
> 
> Given the 2 or 3 implementations floating around, I imagine it wouldn't be 
> hard to integrate for both windows and linux.

Hey, those are a handy pair of functions.
I just implemented a backtrace handler for Tango using those.

The source is attached.

Features:
* Produces stacktraces (obviously).
* Easy to use: just make sure it gets linked in (e.g. by importing 
trace.backtrace and using DSSS). The static constructor will then 
register as a stack trace provider with the runtime, and every exception 
will contain a stack trace.
* Uses a slightly modified std.demangle (just enough to get it to 
compile with Tango) to demangle function names.
* Filters out initial frames from its own module since they're not 
particularly interesting.
* Lazily converts a stack trace to strings. Traces that are never 
printed only allocate the trace object and a list of return addresses. 
Stack traces that are printed multiple times only allocate the strings once.
* Shouldn't be hard to port to Phobos.

Less desirable behavior:
* toString() returns a fresh string every time. This could be prevented 
with some more bookkeeping but I'm not sure it's worth it.


Everyone: feel free to use this any way you want. In particular, feel 
free to commit this to the Tango, Phobos and/or druntime repositories :).


Example:
=====
$ cat test.d
module test;

import trace.backtrace; // just so DSSS picks it up.

void main() {
     foo();
}

void foo() {
     bar();
}

void bar() {
     throw new Exception("Just showing off");
}
$ dsss build
[[[snip]]]
$ ./test
object.Exception: Just showing off
----------------
./test(class Exception object.Exception._ctor(char[], class 
Exception)+0x24) [0x42b174]
./test(void test.bar()+0x37) [0x4186ba]
./test(void test.foo()+0x9) [0x418681]
./test(_Dmain+0x9) [0x418671]
./test [0x42dece]
./test [0x42dfae]
./test [0x42e540]
./test [0x42dfae]
./test(_d_run_main+0xbb) [0x42e42b]
/lib/libc.so.6(__libc_start_main+0xf4) [0x7fd1aacff1c4]
./test [0x4185d9]
=====
Note: the trace may be wrapped in your newsreader.
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