Thread overview
How to catch line number of exception without catching it ?
Dec 13
Thomas
Dec 13
Nathan S.
December 13
Hi forks!

I wanted to ask if there is a way to catch the line position on an exception without setting a try + catch block ?
What I want is something like this:


module main;

import std.stdio;
import std.conv;

void foo()
{
	scope(failure)
	{
		writeln("Got a failure in ", __FILE__, " ", __FUNCTION__, "!" );
		// what I miss is the line position with __LINE__
	}
	
	int x = to!int("1x");  // <-- here is the exception throwing

}

int main()
{
	foo();
	return 0;
}


My goal is to trace the failure from the branch back to the root like this:

(error) in "module2" at "foo2()" on line "..."
(error) in "module1" at "foo1()" on line "..."
(error) in "main" at "main()" on line "..."

I don't want to set on every function a try + catch functionality because I think it is not a good coding style. Also I dont want to send on every possible position where an exception/error could happen (even when catched) the line position into an error log function. So I got the idea of writing out modulename and function with scope(failure) on the beginning of each function, which works great recursive, but only the line position is missing.
So my question is: Is there a way to catch that line where the exception has happened without a catch ?

Or is there a better solution for tracing the error position from root till the branch ?

Thank you for your time!
December 13
On Wednesday, December 13, 2017 18:24:09 Thomas via Digitalmars-d-learn wrote:
> Hi forks!
>
> I wanted to ask if there is a way to catch the line position on
> an exception without setting a try + catch block ?
> What I want is something like this:
>
>
> module main;
>
> import std.stdio;
> import std.conv;
>
> void foo()
> {
>   scope(failure)
>   {
>       writeln("Got a failure in ", __FILE__, " ", __FUNCTION__, "!" );
>       // what I miss is the line position with __LINE__
>   }
>
>   int x = to!int("1x");  // <-- here is the exception throwing
>
> }
>
> int main()
> {
>   foo();
>   return 0;
> }
>
>
> My goal is to trace the failure from the branch back to the root like this:
>
> (error) in "module2" at "foo2()" on line "..."
> (error) in "module1" at "foo1()" on line "..."
> (error) in "main" at "main()" on line "..."
>
> I don't want to set on every function a try + catch functionality
> because I think it is not a good coding style. Also I dont want
> to send on every possible position where an exception/error could
> happen (even when catched) the line position into an error log
> function. So I got the idea of writing out modulename and
> function with scope(failure) on the beginning of each function,
> which works great recursive, but only the line position is
> missing.
> So my question is: Is there a way to catch that line where the
> exception has happened without a catch ?
>
> Or is there a better solution for tracing the error position from root till the branch ?

If you want access to an exception in flight, you must catch it and rethrow it. There is no other way.

But normally, if you want to see the stack when an exception was thrown, you'd either use a debugger, or you'd look at the stack trace that gets printed when the exception exits main (though unfortunately, as I understand it, there's currently a regression, and the line numbers don't show up in stack traces on Linux anymore, even when you compile with -g).

- Jonathan M Davis

December 13
On Wednesday, 13 December 2017 at 18:24:09 UTC, Thomas wrote:
> So my question is: Is there a way to catch that line where the exception has happened without a catch ?

Yes: use a debugger.
December 14
On Wednesday, 13 December 2017 at 18:24:09 UTC, Thomas wrote:
> Or is there a better solution for tracing the error position from root till the branch ?
>

Speaking of tracing exceptions, here's my favourite one .. so far ;-)
(I mean come on.. debugging is great fun!)

btw. If you compile/run this code on Windows, using LDC, you'll get a nice little beep from the speaker (when it runs).

// ------------
module test;

import std.stdio;

void main()
{
    auto str = "hello";
    string * ptr = &str;
    writeln(ptr[1]);   //compile without using the -O option
    // writeln(ptr.ptr[1]); // the above line was meant to be this line.
}
// ------------