Add comment to awk.h regarding the potential lack of NUL-termination for strings.

1 files changed, 7 insertions, 0 deletions

diff --git a/awk.h b/awk.h
index 1d1e4fb8..c737c16b 100644
--- a/awk.h
+++ b/awk.h
@@ -476,6 +476,13 @@ typedef struct exp_node {
 #define re_cnt	flags
 
 /* Node_val */
+/*
+ * Note that the string in stptr may not be NUL-terminated, but it is
+ * guaranteed to have at least one extra byte that may be temporarily set
+ * to '\0'. This is helpful when calling functions such as strtod that require
+ * a NUL-terminated argument. In particular, field values $n for n > 0 and
+ * n < NF will not have a NUL terminator, since they point into the $0 buffer.
+ */
 #define stptr	sub.val.sp
 #define stlen	sub.val.slen
 #define valref	sub.val.sref