Properly handle *snprintf() errors Posix guarantees that the resulting string is null-terminated, even if we have an overflow. Instead of doing what has already been done, properly warn when there has been an error or overflow, so the user can do something about it.
Laslo Hunhold dev@frign.de
Thu, 17 May 2018 23:23:28 +0200
2 files changed,
17 insertions(+),
12 deletions(-)
M
slstatus.c
→
slstatus.c
@@ -1,4 +1,5 @@
/* See LICENSE file for copyright and license details. */ +#include <errno.h> #include <locale.h> #include <signal.h> #include <stdio.h>@@ -53,7 +54,7 @@ {
struct sigaction act; struct timespec start, current, diff, intspec, wait; size_t i, len; - int sflag; + int sflag, ret; char status[MAXLEN]; sflag = 0;@@ -88,12 +89,16 @@ status[0] = '\0';
for (i = len = 0; i < LEN(args); i++) { const char * res = args[i].func(args[i].args); res = (res == NULL) ? unknown_str : res; - len += snprintf(status + len, sizeof(status) - len, - args[i].fmt, res); - - if (len >= sizeof(status)) { - status[sizeof(status) - 1] = '\0'; + if ((ret = snprintf(status + len, sizeof(status) - len, + args[i].fmt, res)) < 0) { + fprintf(stderr, "snprintf: %s\n", + strerror(errno)); + break; + } else if ((size_t)ret >= sizeof(status) - len) { + fprintf(stderr, "snprintf: Output truncated\n"); + break; } + len += ret; } if (sflag) {
M
util.c
→
util.c
@@ -10,15 +10,15 @@ const char *
bprintf(const char *fmt, ...) { va_list ap; - size_t len; + int ret; va_start(ap, fmt); - len = vsnprintf(buf, sizeof(buf) - 1, fmt, ap); - va_end(ap); - - if (len >= sizeof(buf)) { - buf[sizeof(buf)-1] = '\0'; + if ((ret = vsnprintf(buf, sizeof(buf), fmt, ap)) < 0) { + fprintf(stderr, "vsnprintf: %s\n", strerror(errno)); + } else if ((size_t)ret >= sizeof(buf)) { + fprintf(stderr, "vsnprintf: Output truncated\n"); } + va_end(ap); return buf; }