sam: fix bogus clang compiler warning

Strictly speaking this is a compiler bug:

 https://llvm.org/bugs/show_bug.cgi?id=22062

The C11 standard section 6.4.4.3 says:

 "An identifier declared as an enumeration constant has type int."

and 6.7.2.2:

 "Each enumerated type shall be compatible with char, a signed
  integer type, or an unsigned integer type. The choice of type is
  implementation-defined, but shall be capable of representing
  the values of all the members of the enumeration."

So while `err` can store a value larger than that of any enumeration
member, it could also be of signed type, resulting in a warning about
comparing integers of different signs.

Converting it to size_t before the range check and array indexing,
should fix both warnings.

Fix #478

1 files changed, 2 insertions, 1 deletions

diff --git a/sam.c b/sam.c
index e123b56..00b5e1a 100644
--- a/sam.c
+++ b/sam.c
@@ -431,7 +431,8 @@ const char *sam_error(enum SamError err) {
 		[SAM_ERR_GROUP_INVALID_CMD] = "Destructive command in group",
 	};
 
-	return err < LENGTH(error_msg) ? error_msg[err] : NULL;
+	size_t idx = err;
+	return idx < LENGTH(error_msg) ? error_msg[idx] : NULL;
 }
 
 static void change_free(Change *c) {