Quality of errors in DMD
John Colvin via Digitalmars-d
digitalmars-d at puremagic.com
Fri Sep 2 11:06:08 PDT 2016
On Friday, 2 September 2016 at 14:26:37 UTC, Ethan Watson wrote:
> Can we have a serious discussion in here about the quality of
> DMD errors?
> I've been alternately a dog chasing its own tail, and a dog
> barking at a fire hydrant, chasing down errors deep in
> templated and mixin code over the last day. This has resulted
> in manually reducing templates and mixins by hand until I get
> to the root of the problem, which then results in submitting a
> bug and devising an ugly workaround.
> And then I get this one in some code:
> Assertion failure: '0' on line 1492 in file 'glue.c'
> The problem ended up being that a symbol tucked away in a
> template that itself was tucked away in a template was
> undefined, but it couldn't tell me that. Rather, it just
> assert(0)'d and terminated. Rather less helpfully, the only
> meaningful information it could give me at the assert point
> (Could it add to it further down the stack? Maybe?) was defined
> out because DMD wasn't in a debug build.
> Honestly, I find stuff like this in a compiler unacceptable.
> Using assert(0) as shorthand for an unexpected error is all
> fine and dandy until you put your product in the hands of the
> masses and they expect your program to at least give you some
> idea of what was going wrong rather than just crashing out in
> So just for fun, I searched DMD for all instances of assert(0)
> in the code base.
> 830 matches in DMD 2.070.2.
> That's 830 possible places where the compiler will give the
> user virtually no help to track down what (if anything) they
> did wrong.
> DMD certainly isn't the only compiler guilty of this. The .NET
> compiler gives precisely no useful information if it encounters
> SSE types in C++ headers for example. But compared to MSVC,
> I've found the error reporting of DMD to be severely lacking.
> In most cases with MSVC, I have an error code that I can google
> for which is (sometimes) thoroughly documented. And thanks to
> being a widely used product, Stack Overflow usually gives me
> results that I can use in my sleuthing.
> I know I'm also seeing more errors than most because I'm doing
> the kind of code most people don't do. But I'm certainly of the
> opinion that searching for a compiler error code is far easier
> than trying to trick google in to matching the text of my error
ICEs like that are always, always compiler bugs. It would be good
if it said that in the message and told you to report it...
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