Re: [PATCH] Add condition coverage profiling

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 05/04/2022 22:07, Jørgen Kvalsvik wrote:
>>> In action it looks pretty similar to the branch coverage. The -g short
>>> opt carries no significance, but was chosen because it was an available
>>> option with the upper-case free too.
>>>
>>> gcov --conditions:
>>>
>>>           3:   17:void fn (int a, int b, int c, int d) {
>>>           3:   18:    if ((a && (b || c)) && d)
>>> conditions covered 5/8
>>> condition  1 not covered (false)
>>> condition  2 not covered (true)
>>> condition  2 not covered (false)
>>>           1:   19:        x = 1;
>>>           -:   20:    else
>>>           2:   21:        x = 2;
>>>           3:   22:}
>> I have some trouble to understand the output. Would 8/8 mean that we have 100%
>> MC/DC coverage? What does "not covered (false)" or "not covered (true)" mean?
>>
> Yes, 8/8 would mean that the expression is 100% covered (all conditions take on
> both values and have independent effect on the outcome). 

This is really great.

> "not covered" is a
> report of missing coverage, that is "condition  1 not covered (false)" means
> that bit N (N = 1, b in this case) has not taken on false yet, and to achieve
> 100% coverage you need a test case where b = false.
> 
> The wording is arbitrary, and I tried to strike a balance between density,
> clarity, grepability and noise. I am open to other suggestions that would
> improve this.

Ok, for the default output this is good. The output can be explained in 
the documentation. I will try to help here.

In theory, would it be possible to print the state of the truth table 
with the information available in the gcda and gcno files? For example:

Truth table for: a && (b || c)) && d

0 | 1 | 2 | 3 || covered
--+---+---+---++--------
0 | X | X | X || Y
0 | X | X | X || Y
0 | X | X | X || Y
0 | X | X | X || Y
0 | X | X | X || Y
0 | X | X | X || Y
0 | X | X | X || Y
0 | X | X | X || Y
1 | 0 | 0 | X || N
1 | 0 | 0 | X || N
1 | 0 | 1 | 0 || N
1 | 0 | 1 | 1 || N
1 | 1 | X | 0 || Y
1 | 1 | X | 0 || Y
1 | 1 | X | 1 || Y
1 | 1 | X | 1 || Y

Would it be possible to map the condition index to a source code 
snippet? For example condition 1 to "b"?

> 
> Unrelated to this, in typing up some notes on this I found a few minor and one
> quite significant (really, the masking algorithm is broken) error in the
> algorithm, which I am working on correcting. I will propose the new patch with
> these fixes too once I have finished writing and testing it.

Thanks a lot for this work.

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