[hackers] [sbase] [PATCH] tail: Don't print garbage when input contains no newlines.

From: Wolfgang Corcoran-Mathe <first.lord.of.teal_AT_gmail.com>
Date: Fri, 28 Aug 2015 00:10:02 -0400

getline(3) expects newline-terminated input. While glibc's
implementation seems to catch unterminated input and zero the
buffer, other versions (notably musl's) do not.

This is a workaround. Garbage will still be read, but
not printed.

---
 tail.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/tail.c b/tail.c
index 306bbc1..417289f 100644
--- a/tail.c
+++ b/tail.c
_AT_@ -39,6 +39,7 @@ taketail(FILE *fp, const char *str, size_t n)
 	Rune *r = NULL;
 	char **ring = NULL;
 	size_t i, j, *size = NULL;
+	int seenln = 0;
 
 	if (!n)
 		return;
_AT_@ -47,7 +48,7 @@ taketail(FILE *fp, const char *str, size_t n)
 		ring = ecalloc(n, sizeof(*ring));
 		size = ecalloc(n, sizeof(*size));
 
-		for (i = j = 0; getline(ring + i, size + i, fp) > 0; )
+		for (i = j = 0; getline(ring + i, size + i, fp) > 0; seenln = 1)
 			i = j = (i + 1) % n;
 	} else {
 		r = ecalloc(n, sizeof(*r));
_AT_@ -59,7 +60,7 @@ taketail(FILE *fp, const char *str, size_t n)
 		eprintf("%s: read error:", str);
 
 	do {
-		if (ring && ring[j]) {
+		if (seenln && ring && ring[j]) {
 			fputs(ring[j], stdout);
 			free(ring[j]);
 		} else if (r) {
-- 
2.3.5

Received on Fri Aug 28 2015 - 06:10:02 CEST