wip: Build with -Wconversionlukeshu/safe-conversion

I think this found a real bug in the dhcp packet parser.

I don't think anything called lib9p_str{,n}() values that could be big
enough, but their bounds-checking was broken.

2 files changed, 13 insertions, 5 deletions

diff --git a/libmisc/tests/test_obj_nest.c b/libmisc/tests/test_obj_nest.c
index bb9d6de..be303f2 100644
--- a/libmisc/tests/test_obj_nest.c
+++ b/libmisc/tests/test_obj_nest.c
@@ -5,6 +5,10 @@
  */
 
 #include <string.h> /* for memcpy() */
+#include <limits.h>   /* for SSIZE_MAX, not set by newlib */
+#ifndef SSIZE_MAX
+#define SSIZE_MAX (SIZE_MAX >> 1)
+#endif
 
 #include <libmisc/obj.h>
 
@@ -45,8 +49,10 @@ static ssize_t myclass_read(struct myclass *self, void *buf, size_t count) {
 	test_assert(self);
 	if (count > self->len)
 		count = self->len;
+	if (count > SSIZE_MAX)
+		count = SSIZE_MAX;
 	memcpy(buf, self->buf, count);
-	return count;
+	return (ssize_t)count;
 }
 
 static ssize_t myclass_write(struct myclass *self, void *buf, size_t count) {
@@ -55,9 +61,11 @@ static ssize_t myclass_write(struct myclass *self, void *buf, size_t count) {
 		return -1;
 	if (count > sizeof(self->buf))
 		count = sizeof(self->buf);
+	if (count > SSIZE_MAX)
+		count = SSIZE_MAX;
 	memcpy(self->buf, buf, count);
 	self->len = count;
-	return count;
+	return (ssize_t)count;
 }
 
 /* main test body *************************************************************/
diff --git a/libmisc/tests/test_rand.c b/libmisc/tests/test_rand.c
index 02f4c1c..b98dacf 100644
--- a/libmisc/tests/test_rand.c
+++ b/libmisc/tests/test_rand.c
@@ -53,14 +53,14 @@ static void test_n(uint64_t cnt) {
 		bool seen[MAX_SEE_ALL] = {0};
 		for (int i = 0; i < ROUNDS; i++) {
 			uint64_t val = rand_uint63n(cnt);
-			sum += val;
+			sum += (double)val;
 			test_assert(val < cnt);
 			if (cnt < MAX_SEE_ALL)
 				seen[val] = true;
 		}
 		if (cnt > 1) {
-			test_assert(sum/ROUNDS > 0.45*(cnt-1));
-			test_assert(sum/ROUNDS < 0.55*(cnt-1));
+			test_assert(sum/ROUNDS > 0.45*(double)(cnt-1));
+			test_assert(sum/ROUNDS < 0.55*(double)(cnt-1));
 		}
 		if (cnt < MAX_SEE_ALL) {
 			for (uint64_t i = 0; i < cnt; i++)