aft: Silence format-overflow warning with gcc-10.

	aft.c: In function 'print_list_item':
	aft.c:736:17: warning: '%*u' directive writing between 1 and 65529 bytes into a region of size 30 [-Wformat-overflow=]
	  736 |   sprintf(buf, "%*u:%02u:%02d", max_width - 6, hours, mins,
	      |                 ^~~
	aft.c:736:16: note: directive argument in the range [1, 4294967295]
	  736 |   sprintf(buf, "%*u:%02u:%02d", max_width - 6, hours, mins,
	      |                ^~~~~~~~~~~~~~~
	aft.c:736:16: note: directive argument in the range [-59, 59]
	aft.c:736:3: note: 'sprintf' output between 8 and 65545 bytes into a destination of size 30
	  736 |   sprintf(buf, "%*u:%02u:%02d", max_width - 6, hours, mins,
	      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	  737 |    seconds % 60);
	      |    ~~~~~~~~~~~~~

The code is correct but gcc can't prove it. Silence the warning by
passing the size of the buffer and asserting that it won't overflow
before printing to it.

diff --git a/aft.c b/aft.c
index eb955e019f538e3d73f38074ff657c9b86d2199d..b358c96cd9afd23bfa7f043c8add8bbf8b4bfade 100644 (file)
--- a/aft.c
+++ b/aft.c
@@ -721,7 +721,8 @@ __a_const static short unsigned get_duration_width(int seconds)
        return width + 6;
 }
 
-static void get_duration_buf(int seconds, char *buf, struct ls_options *opts)
+static void get_duration_buf(int seconds, char *buf, size_t bufsize,
+               struct ls_options *opts)
 {
        unsigned hours = seconds / 3600, mins = (seconds % 3600) / 60;
        short unsigned max_width;
@@ -729,10 +730,12 @@ static void get_duration_buf(int seconds, char *buf, struct ls_options *opts)
        if (!hours) { /* m:ss or mm:ss */
                max_width = opts->mode == LS_MODE_LONG?
                        opts->widths.duration_width : 4;
+               assert(max_width < bufsize - 1);
                sprintf(buf, "%*u:%02d", max_width - 3, mins, seconds % 60);
        } else { /* more than one hour => h:mm:ss, hh:mm:ss, hhh:mm:ss, ... */
                max_width = opts->mode == LS_MODE_LONG?
                        opts->widths.duration_width : 7;
+               assert(max_width < bufsize - 1);
                sprintf(buf, "%*u:%02u:%02d", max_width - 6, hours, mins,
                        seconds % 60);
        }
@@ -856,7 +859,8 @@ static int print_list_item(struct ls_data *d, struct ls_options *opts,
                if (ret < 0)
                        goto out;
        }
-       get_duration_buf(afhi->seconds_total, duration_buf, opts);
+       get_duration_buf(afhi->seconds_total, duration_buf,
+               sizeof(duration_buf), opts);
        if (opts->mode == LS_MODE_LONG) {
                struct ls_widths *w = &opts->widths;
                if (lls_opt_given(r_a))