Escaping Safety with Debug Statements

Question

I know of

debug writeln("Some good debug message")

in pure functions but what about functions that I have carefully tagged as @safe or @trusted? DMD currently doesn't allow debug writeln's in those because writeln and similar are currently @system. This is IMHO very frustrating. Is there a clever way to escape safety or do I have to temporarily comment out all my @safe and @trusted tags?

score 5 · Accepted Answer · answered Oct 16 '13 at 20:59

5

What I do is make my own @trusted debug_writeln.

@trusted void debug_writeln(T...)(T t) {
      import std.stdio;
      writeln(t);
}

Since this is @trusted, it will work inside @safe functions without changing anything. You can also just call it writeln and then don't import std.stdio or alias to force the disambiguation.

answered Oct 16 '13 at 20:59

Adam D. Ruppe

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Great! I knew you guys had a solution ;) – Nordlöw Oct 16 '13 at 21:25
I believe this is what we all do, for now. :) – DejanLekic Oct 17 '13 at 10:21
this is bad if T has an unsafe to!string method – Demi Oct 25 '13 at 20:40

score 2 · Answer 2 · answered Oct 16 '13 at 21:02

A generic solution

import std.stdio;

void main () @safe pure
{
    auto str = trustedPureDebugCall!readln();
    trustedPureDebugCall!writeln(str);
}

debug auto trustedPureDebugCall (alias fn, A...) (A args) @trusted pure
{
     debug return fn(args);
}

Escaping Safety with Debug Statements

2 Answers2