Re: [PATCH] Add condition coverage profiling

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

Hello Jørgen,

thanks for the updated patch. I used it for a test suite run and the 
results look quite good.

Could you please add this hunk to your patch set:

diff --git a/libgcc/libgcov-merge.c b/libgcc/libgcov-merge.c
index 89741f637e1..9e3e8ee5657 100644
--- a/libgcc/libgcov-merge.c
+++ b/libgcc/libgcov-merge.c
@@ -33,6 +33,11 @@ void __gcov_merge_add (gcov_type *counters 
__attribute__ ((unused)),
                         unsigned n_counters __attribute__ ((unused))) {}
  #endif

+#ifdef L_gcov_merge_ior
+void __gcov_merge_ior (gcov_type *counters  __attribute__ ((unused)),
+                      unsigned n_counters __attribute__ ((unused))) {}
+#endif
+
  #ifdef L_gcov_merge_topn
  void __gcov_merge_topn (gcov_type *counters  __attribute__ ((unused)),
                         unsigned n_counters __attribute__ ((unused))) {}

It is necessary to use gcov in freestanding environments (inhibit_libc 
is defined).

The condition profiling found one spot for which we have insufficient 
condition coverage:

function _Leap_year called 227 returned 100% blocks executed 100%
       227:   54:static bool _Leap_year(
         -:   55:  uint32_t year
         -:   56:)
         -:   57:{
       227:   58:  return (((year % 4) == 0) && ((year % 100) != 0)) || 
((year % 400) == 0);
branch  0 taken 19% (fallthrough)
branch  1 taken 81%
branch  2 taken 16% (fallthrough)
branch  3 taken 84%
branch  4 taken 4% (fallthrough)
branch  5 taken 96%
conditions covered 5/6
condition  1 not covered (false)
         -:   59:}

This is because we don't test with the year 2100 for example. This value 
would result in:

year % 4 == 0: true
year % 100 != 0: false
year % 400 == 0: false

It was not immediately clear to me what the

"conditions covered 5/6
condition  1 not covered (false)"

is supposed to tell me. I guess a reasonable interpretation is: 
condition 1 (which is "(year % 100) != 0" should be false and determine 
the outcome of the decision.

What could be a bit confusing is that we have "conditions covered 5/6", 
however, there are only three conditions (0: (year % 4) == 0, 1: (year % 
100) != 0, 2: (year % 400) == 0). Maybe it would be more clear if the 
report says "condition variants covered 5/6" or something like this.

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