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
flames.
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
message.
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...
