When ensuring the destination buffer is truncated for a string obtained

from a BIF, use the size of the destinatino buffer, not the length of the
string to determine where to put the nul char.  As a side effect, the
old code would truncate the string by one character while it was possibly
overflowing the buffer.

sys/dev/acpica/acpi_cmbat.c

@@ -93,7 +93,7 @@ static int acpi_cmbat_units = 0;
 	default:							\
 		goto label;						\
 	}								\
-	dest[length-1] = '\0';						\
+	dest[sizeof(dest)-1] = '\0';					\
 } while(0)
 
 static void