Hello Jørgen,
having support for MC/DC coverage in GCC would be really nice. I tried
out your latest patch on an arm cross-compiler with Newlib (inhibit_libc
is defined). Could you please add the following fix to your patch:
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 seems that support for the new GCOV_TAG_CONDS is missing in gcov-tool
and gcov-dump, see "tag_table" in gcc/gcov-dump.c and libgcc/libgcov-util.c.
On 21/03/2022 12:55, Jørgen Kvalsvik via Gcc-patches wrote:
[...]
Like Wahlen et al this implementation uses bitsets to store conditions,
which gcov later interprets. This is very fast, but introduces an max
limit for the number of terms in a single boolean expression. This limit
is the number of bits in a gcov_unsigned_type (which is typedef'd to
uint64_t), so for most practical purposes this would be acceptable.
limitation can be relaxed with a more sophisticated way of storing and
updating bitsets (for example length-encoding).
For multi-threaded applications using -fprofile-update=atomic is quite
important. Unfortunately, not all 32-bit targets support 64-bit atomic
operations in hardware. There is a target hook to select the size of
gcov_type. Maybe a dedicated 64-bit type should be used for the bitfield
using two 32-bit atomic OR if necessary.
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?
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