a workaround in the meantime is to modify the _CSMITH_BITFIELD macro in runtime/random_inc.h so that it never returns 0 when applied to an argument different from 0. Something like (VERY little tested):
diff --git a/runtime/random_inc.h b/runtime/random_inc.h
index 7559cbd..c037bee 100644
--- a/runtime/random_inc.h
+++ b/runtime/random_inc.h
@@ -102,7 +102,7 @@ char __executed_checks[N_WRAP+1];
#endif
#define INT_BIT (sizeof(int)*CHAR_BIT)
-#define _CSMITH_BITFIELD(x) (((x)>INT_BIT)?((x)%INT_BIT):(x))
+#define _CSMITH_BITFIELD(x) (((x)>INT_BIT)?((((x)%INT_BIT)?((x)%INT_BIT):1)):(x))
#ifdef TCC