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libc: actual overrun checks in strftime; fix %z to use proper format

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This commit is contained in:
K. Lange 2023-12-23 12:41:11 +09:00
parent 7aaeec1eba
commit a535a2cdac
1 changed files with 50 additions and 44 deletions
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94
libc/time/strftime.c
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@ -38,15 +38,15 @@ static char * months_short[] = {
size_t strftime(char *s, size_t max, const char *fmt, const struct tm *tm) { size_t strftime(char *s, size_t max, const char *fmt, const struct tm *tm) {
if (!tm) { if (!tm) {
if (max < sizeof("[tm is null]")) return 0;
return sprintf(s, "[tm is null]"); return sprintf(s, "[tm is null]");
} }
char * b = s; char * b = s;
size_t count = 0;
for (const char *f = fmt; *f; f++) { for (const char *f = fmt; *f; f++) {
if (*f != '%') { if (*f != '%') {
count++; if (max == 0) return 0;
max--;
*b++ = *f; *b++ = *f;
if (count == max) return b - s;
continue; continue;
} }
++f; ++f;
@ -61,22 +61,23 @@ size_t strftime(char *s, size_t max, const char *fmt, const struct tm *tm) {
} }
(void)_alte; /* TODO: Implement these */ (void)_alte; /* TODO: Implement these */
(void)_alto; (void)_alto;
int w = 0;
switch (*f) { switch (*f) {
case 'a': case 'a':
b += sprintf(b, "%s", weekdays_short[tm->tm_wday]); w = snprintf(b, max, "%s", weekdays_short[tm->tm_wday]);
break; break;
case 'A': case 'A':
b += sprintf(b, "%s", weekdays[tm->tm_wday]); w = snprintf(b, max, "%s", weekdays[tm->tm_wday]);
break; break;
case 'h': case 'h':
case 'b': case 'b':
b += sprintf(b, "%s", months_short[tm->tm_mon]); w = snprintf(b, max, "%s", months_short[tm->tm_mon]);
break; break;
case 'B': case 'B':
b += sprintf(b, "%s", months[tm->tm_mon]); w = snprintf(b, max, "%s", months[tm->tm_mon]);
break; break;
case 'c': case 'c':
b += sprintf(b, "%s %s %02d %02d:%02d:%02d %04d", w = snprintf(b, max, "%s %s %02d %02d:%02d:%02d %04d",
weekdays_short[tm->tm_wday], weekdays_short[tm->tm_wday],
months_short[tm->tm_mon], months_short[tm->tm_mon],
tm->tm_mday, tm->tm_mday,
@ -86,119 +87,124 @@ size_t strftime(char *s, size_t max, const char *fmt, const struct tm *tm) {
tm->tm_year + 1900); tm->tm_year + 1900);
break; break;
case 'C': case 'C':
b += sprintf(b, "%02d", (tm->tm_year + 1900) / 100); w = snprintf(b, max, "%02d", (tm->tm_year + 1900) / 100);
break; break;
case 'd': case 'd':
b += sprintf(b, "%02d", tm->tm_mday); w = snprintf(b, max, "%02d", tm->tm_mday);
break; break;
case 'D': case 'D':
b += sprintf(b, "%02d/%02d/%02d", tm->tm_mon+1, tm->tm_mday, tm->tm_year % 100); w = snprintf(b, max, "%02d/%02d/%02d", tm->tm_mon+1, tm->tm_mday, tm->tm_year % 100);
break; break;
case 'e': case 'e':
b += sprintf(b, "%2d", tm->tm_mday); w = snprintf(b, max, "%2d", tm->tm_mday);
break; break;
case 'F': case 'F':
b += sprintf(b, "%04d-%02d-%02d", tm->tm_year + 1900, tm->tm_mon+1, tm->tm_mday); w = snprintf(b, max, "%04d-%02d-%02d", tm->tm_year + 1900, tm->tm_mon+1, tm->tm_mday);
break; break;
case 'H': case 'H':
b += sprintf(b, "%02d", tm->tm_hour); w = snprintf(b, max, "%02d", tm->tm_hour);
break; break;
case 'I': case 'I':
b += sprintf(b, "%02d", tm->tm_hour == 0 ? 12 : (tm->tm_hour == 12 ? 12 : (tm->tm_hour % 12))); w = snprintf(b, max, "%02d", tm->tm_hour == 0 ? 12 : (tm->tm_hour == 12 ? 12 : (tm->tm_hour % 12)));
break; break;
case 'j': case 'j':
b += sprintf(b, "%03d", tm->tm_yday); w = snprintf(b, max, "%03d", tm->tm_yday);
break; break;
case 'k': case 'k':
b += sprintf(b, "%2d", tm->tm_hour); w = snprintf(b, max, "%2d", tm->tm_hour);
break; break;
case 'l': case 'l':
b += sprintf(b, "%2d", tm->tm_hour == 0 ? 12 : (tm->tm_hour == 12 ? 12 : (tm->tm_hour % 12))); w = snprintf(b, max, "%2d", tm->tm_hour == 0 ? 12 : (tm->tm_hour == 12 ? 12 : (tm->tm_hour % 12)));
break; break;
case 'm': case 'm':
b += sprintf(b, "%02d", tm->tm_mon+1); w = snprintf(b, max, "%02d", tm->tm_mon+1);
break; break;
case 'M': case 'M':
b += sprintf(b, "%02d", tm->tm_min); w = snprintf(b, max, "%02d", tm->tm_min);
break; break;
case 'n': case 'n':
b += sprintf(b, "\n"); w = snprintf(b, max, "\n");
break; break;
case 'p': case 'p':
b += sprintf(b, "%s", tm->tm_hour < 12 ? "AM" : "PM"); w = snprintf(b, max, "%s", tm->tm_hour < 12 ? "AM" : "PM");
break; break;
case 'P': case 'P':
b += sprintf(b, "%s", tm->tm_hour < 12 ? "am" : "pm"); w = snprintf(b, max, "%s", tm->tm_hour < 12 ? "am" : "pm");
break; break;
case 'r': case 'r':
b += sprintf(b, "%02d:%02d:%02d %s", w = snprintf(b, max, "%02d:%02d:%02d %s",
tm->tm_hour == 0 ? 12 : (tm->tm_hour == 12 ? 12 : (tm->tm_hour % 12)), tm->tm_hour == 0 ? 12 : (tm->tm_hour == 12 ? 12 : (tm->tm_hour % 12)),
tm->tm_min, tm->tm_min,
tm->tm_sec, tm->tm_sec,
tm->tm_hour < 12 ? "AM" : "PM"); tm->tm_hour < 12 ? "AM" : "PM");
break; break;
case 'R': case 'R':
b += sprintf(b, "%02d:%02d", w = snprintf(b, max, "%02d:%02d",
tm->tm_hour, tm->tm_hour,
tm->tm_min); tm->tm_min);
break; break;
case 's': case 's':
b += sprintf(b, "%ld", mktime((struct tm*)tm)); w = snprintf(b, max, "%ld", mktime((struct tm*)tm));
break; break;
case 'S': case 'S':
b += sprintf(b, "%02d", tm->tm_sec); w = snprintf(b, max, "%02d", tm->tm_sec);
break; break;
case 't': case 't':
b += sprintf(b, "\t"); w = snprintf(b, max, "\t");
break; break;
case 'T': case 'T':
b += sprintf(b, "%02d:%02d:%02d", w = snprintf(b, max, "%02d:%02d:%02d",
tm->tm_hour, tm->tm_hour,
tm->tm_min, tm->tm_min,
tm->tm_sec); tm->tm_sec);
break; break;
case 'u': case 'u':
b += sprintf(b, "%d", tm->tm_wday == 0 ? 7 : tm->tm_wday); w = snprintf(b, max, "%d", tm->tm_wday == 0 ? 7 : tm->tm_wday);
break; break;
case 'w': case 'w':
b += sprintf(b, "%d", tm->tm_wday); w = snprintf(b, max, "%d", tm->tm_wday);
break; break;
case 'x': case 'x':
b += sprintf(b, "%02d/%02d/%02d", tm->tm_mon+1, tm->tm_mday, tm->tm_year % 100); w = snprintf(b, max, "%02d/%02d/%02d", tm->tm_mon+1, tm->tm_mday, tm->tm_year % 100);
break; break;
case 'X': case 'X':
b += sprintf(b, "%02d:%02d:%02d", w = snprintf(b, max, "%02d:%02d:%02d",
tm->tm_hour, tm->tm_hour,
tm->tm_min, tm->tm_min,
tm->tm_sec); tm->tm_sec);
break; break;
case 'y': case 'y':
b += sprintf(b, "%02d", tm->tm_year % 100); w = snprintf(b, max, "%02d", tm->tm_year % 100);
break; break;
case 'Y': case 'Y':
b += sprintf(b, "%04d", tm->tm_year + 1900); w = snprintf(b, max, "%04d", tm->tm_year + 1900);
break;
case 'z': {
int zone_offset = tm->_tm_zone_offset >= 0 ? tm->_tm_zone_offset : -tm->_tm_zone_offset;
char sign = tm->_tm_zone_offset >= 0 ? '+' : '-';
int hour = zone_offset / 3600;
int mins = (zone_offset / 60) % 60;
w = snprintf(b, max, "%c%02d%02d", sign, hour, mins);
break; break;
case 'z':
if (tm->_tm_zone_offset >= 0) {
b += sprintf(b, "+%04d", tm->_tm_zone_offset);
} else {
b += sprintf(b, "-%04d", -tm->_tm_zone_offset);
} }
break;
case 'Z': case 'Z':
b += sprintf(b, tm->_tm_zone_name); w = snprintf(b, max, tm->_tm_zone_name);
break; break;
case '%': case '%':
b += sprintf(b, "%c", '%'); w = snprintf(b, max, "%c", '%');
break; break;
case 'V': case 'V':
case 'W': case 'W':
case 'U': case 'U':
case 'G': case 'G':
case 'g': case 'g':
b += sprintf(b, "<%c unsupported>", *f); w = snprintf(b, max, "<%c unsupported>", *f);
break; break;
} }
if (w < 0) return 0; /* error while formatting */
if ((size_t)w >= max) return 0; /* output was truncated */
max -= w;
b += w;
} }
/* Ensure the buffer ends in a null */ /* Ensure the buffer ends in a null */
*b = '\0'; *b = '\0';