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.

1 files changed, 10 insertions, 2 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 *************************************************************/