randomize instrumentLimitEvery
In old style, if we run in fork-and-exec mode, `staticCnt` will starts
from zero for each run. So for example `__sanitizer_cov_trace_cmp4` will
only be executed at the 4096th time...
If the target is small to have 4096 cmp during execution,
`__sanitizer_cov_trace_cmp4` trick will never work.
Even if the target is big, the old style is still inbalanced.
So just make it random.
diff --git a/libhfuzz/instrument.c b/libhfuzz/instrument.c
index 1f97dd3..957242e 100644
--- a/libhfuzz/instrument.c
+++ b/libhfuzz/instrument.c
@@ -233,10 +233,7 @@
/* Used to limit certain expensive actions, like adding values to dictionaries */
static inline bool instrumentLimitEvery(uint64_t step) {
- static __thread uint64_t staticCnt = 0;
- if (((staticCnt++) % step) == 0) {
- return true;
- }
+ if (util_rndGet(0, step) == 0) return true;
return false;
}
