[PATCH] misc: Add grub_sprintf() C99/POSIX non-conformance comment

[Glenn Washburn <development@efficientek.com>]

Make clear that grub_sprintf() does not conform to C99/POSIX. It returns
the number of bytes written, even when n is less than the length of the
fully formatted string.

Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 grub-core/kern/misc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/grub-core/kern/misc.c b/grub-core/kern/misc.c
index 2890aad49fa7..634bf1441c63 100644
--- a/grub-core/kern/misc.c
+++ b/grub-core/kern/misc.c
@@ -983,6 +983,7 @@ write_number (char *str, grub_size_t *count, grub_size_t max_len, grub_size_t fo
       write_char (str, count, max_len, zerofill);
 }
 
+/* See grub_snprintf for details of non-compliance to C99 and POSIX */
 static int
 grub_vsnprintf_real (char *str, grub_size_t max_len, const char *fmt0,
 		     struct printf_args *args)
@@ -1204,6 +1205,14 @@ grub_vsnprintf (char *str, grub_size_t n, const char *fmt, va_list ap)
   return ret < n ? ret : n;
 }
 
+/*
+ * Note: grub_snprintf does not conform to C99 nor the POSIX specs.
+ * Specifically, it returns the number of bytes written, minus the NULL
+ * byte. Whereas, the specs say that the return value should be the
+ * number of bytes that *would* be written if n were sufficiently large
+ * to contain the formatted output. This only matters when n is smaller
+ * than the formatted string.
+ */
 int
 grub_snprintf (char *str, grub_size_t n, const char *fmt, ...)
 {
-- 
2.34.1