Code coverage in Phobos

[Basile B. via Digitalmars-d]

On Monday, 28 March 2016 at 16:44:26 UTC, Vladimir Panteleev 
wrote:
> On Monday, 28 March 2016 at 16:10:48 UTC, Basile B. wrote:
>> On Monday, 28 March 2016 at 11:29:55 UTC, Vladimir Panteleev 
>> wrote:
>>> Yep. The difficulties are:
>>>
>>> 1. Getting data off the autotester. Currently it's nearly 
>>> impossible, as is making any changes to it.
>>>
>>> https://issues.dlang.org/show_bug.cgi?id=14381
>>>
>>> 2. Collating data from multiple platforms, as there is a lot 
>>> of platform-specific code in e.g. std.stdio, std.file, and 
>>> most of Druntime.
>>
>> 3. since the coverage is computed at run-time by the 
>> application that runs the tests all the static code (+ CTFE) 
>> is considered NOT covered. This gives misleading results.
>>
>> For example std.traits will probably have a bad coverage while 
>> actually it's pretty good.
>
> Not really an issue since DMD only counts the code that goes 
> into the binary for coverage. Uncovered lines will have seven 
> zeroes before the |, whereas lines with no compiled code will 
> have nothing.

Not true. I wouldn't be able to link an example in Phobos but 
this is a more general issue with coverage. For example take a 
file with:


template isSomething(T)
{
     bool helper()
     {
         return true; // line 5
     }
     enum isSomething = helper;
}

unittest
{
     bool test;
     static if (isSomething!bool)
     {test = true;}
     assert(test);
}

and compile with -main -unittest -cov then run.
the lst file indicates 00000 for line 5.

Actually with `static if()` and helpers functions executed at 
compile time, 100% coverage is unreachchable. This is more or 
less the same that happens with if(__ctfe) branches.