Add comment to gawkapi.h about string termination.

2 files changed, 11 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 24dcaf37..16f7f184 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2016-06-27         Andrew J. Schorr     <aschorr@telemetry-investments.com>
 
+	* gawkapi.h (awk_string): Add comment about the potential lack of
+	NUL-termination.
+
+2016-06-27         Andrew J. Schorr     <aschorr@telemetry-investments.com>
+
 	* awk.h: Add a comment regarding the potential lack of NUL-termination
 	for Node_val strings.
 
diff --git a/gawkapi.h b/gawkapi.h
index f0244604..975f82df 100644
--- a/gawkapi.h
+++ b/gawkapi.h
@@ -278,6 +278,12 @@ enum {
  * The API deals exclusively with regular chars; these strings may
  * be multibyte encoded in the current locale's encoding and character
  * set. Gawk will convert internally to wide characters if necessary.
+ *
+ * Note that the string may not be terminated with a '\0' character.
+ * In particular, this happens for field values $n where n > 0 and n < NF,
+ * since the string points directly into the $0 buffer. All other strings,
+ * including those created by extensions, should be NUL-terminated. In general
+ * though, extension code should not assume that the string is NUL-terminated!
  */
 typedef struct awk_string {
 	char *str;	/* data */