Re: [PATCH] Add condition coverage profiling

[Hans-Peter Nilsson <hp@bitrange.com>]

On Wed, 12 Oct 2022, Jørgen Kvalsvik via Gcc-patches wrote:
> This patch adds support in gcc+gcov for modified condition/decision
> coverage (MC/DC) with the -fprofile-conditions flag.

I'd love improvements in this area.

But this is a serious concern:

> gcov --conditions:
> 
>         3:   17:void fn (int a, int b, int c, int d) {
>         3:   18:    if ((a && (b || c)) && d)
> condition outcomes covered 3/8
> condition  0 not covered (true false)
> condition  1 not covered (true)
> condition  2 not covered (true)
> condition  3 not covered (true)
>         1:   19:        x = 1;
>         -:   20:    else
>         2:   21:        x = 2;
>         3:   22:}

Is this the suggested output from gcov?

Sorry, but this is too hard to read; I can't read this.  What 
does it mean?  What's 0 and what's 1 and which are the 8 
conditions?  (Why not 16 or more; which are redundant?)  Or to 
wit, a glance, which parts of (a && (b || c)) && d are actually 
covered?

There has got to be a better *intuitively* understandable 
presentation format than this. If you please forgive the errors 
in not matching the partal expressions like in your proposal and 
focus on the presentation format, I'd suggest something like, 
for a one-time run with a=true, b=false, c=true, d=false:

"With:
         3:   18:    if ((a && (b || c)) && d)
0:                       ^^^^^^^^^^^^^^^
1:                                          ^
2:                        ^
3:                             ^^^^^^^^
4:                              ^
5:                                   ^
condition  0 not covered (false)
condition  1 not covered (true)
condition  2 not covered (false)
condition  3 not covered (false)
condition  4 not covered (true)
condition  5 not covered (false)"
(etc)

Possibly with each partial expression repeated above its 
underscoring for readability, because of the increasing distance 
between the underscoring and referred source.

Actually, a separate indexed table like that isn't the best 
choice either.  Perhaps better quoting the source:

"condition (a && (b || c)) false not covered
condition d false not covered
condition (b || c) false not covered
condition b true not covered
condition c false not covered"

Or, just underscoring as instead of quoting the source:
"        3:   18:    if ((a && (b || c)) && d)

In condition:            ^^^^^^^^^^^^^^^
false not covered"
(etc)

It is possible I completely misunderstand your proposal, but 
there has to be something from the above to pick.  I'd hate to 
see this go down because of usability problems.  Hope this was 
constructive.

brgds, H-P