scc

commit 108a79e6a070b320c7efd64b51b215d3ff73cb7d
parent 1ead11308a65c7fd1b816a007a597b4569b8c7f3
Author: Roberto E. Vargas Caballero <k0ga@shike2.net>
Date:   Tue, 14 Apr 2026 17:56:38 +0200

libc/time: Force values for all the tzone vars

The tzone variables are used in different places, and they are
assumed to have correct values. This invariant was not enforced
by _tzset() and _tzname[0] and _tzname[1] could have a NULL pointer
that would produce a segmentation fault when the TZ variable
was not set in case of using any of the strftime() specifiers
that require these strings or in the function gmtoff() of
localtime.c.

Diffstat:
M
src/libc/arch/posix/_systime.c
 | 
5
+++--
M
src/libc/arch/posix/_tzone.c
 | 
1
+
M
src/libc/libc.h
 | 
40
++++++++++++++++++++--------------------
M
src/libc/time/localtime.c
 | 
4
+++-

4 files changed, 27 insertions(+), 23 deletions(-)
diff --git a/src/libc/arch/posix/_systime.c b/src/libc/arch/posix/_systime.c
@@ -5,12 +5,13 @@
 time_t
 _systime(struct tm *tm)
 {
+	int i;
 	time_t t = 0;
 	int year = tm->tm_year + MINYEAR;
 
-	for (int i = EPOCH; i < year; ++i)
+	for (i = EPOCH; i < year; ++i)
 		t += _daysyear(i) * SECDAY;
-	for (int i = 0; i < tm->tm_mon; ++i)
+	for (i = 0; i < tm->tm_mon; ++i)
 		t += _daysmon[i] * SECDAY;
 
 	t += tm->tm_sec;
diff --git a/src/libc/arch/posix/_tzone.c b/src/libc/arch/posix/_tzone.c
@@ -230,6 +230,7 @@ _tzset(void)
 	char *tz = getenv("TZ");
 	int i;
 
+	_tzname[1] = _tzname[0] = "UTC";
 	_tzstdoff = _tzdstoff = (time_t) -1;
 	_tzstart = _tzend = (time_t) -1;
 	_tzjulian = 0;
diff --git a/src/libc/libc.h b/src/libc/libc.h
@@ -1,3 +1,17 @@
+struct tm;
+struct _FILE;
+
+void *_getheap(void);
+int _dtoi(char c);
+
+#ifdef stdin
+int _allocbuf(FILE *);
+int _flsbuf(FILE *);
+FILE *_fpopen(const char * restrict, const char *restrict,
+                     FILE *restrict);
+#endif
+
+#ifdef _TIME_H
 enum {
 	SUN,
 	MON,
@@ -19,33 +33,19 @@ enum {
 #define SECHOUR (60 * SECMIN)    /* 3600 */
 #define SECDAY (24 * SECHOUR)   /* 86400 */
 
-struct tm;
-struct _FILE;
-
-void *_getheap(void);
-int _dtoi(char c);
-
-#ifdef stdin
-int _allocbuf(FILE *);
-int _flsbuf(FILE *);
-FILE *_fpopen(const char * restrict, const char *restrict,
-                     FILE *restrict);
-#endif
-
-#ifdef _TIME_H
+/* _tzone.c variables */
 extern time_t _tzstdoff, _tzdstoff;
 extern time_t _tzstart, _tzend;
+extern char *_tzname[2];
+extern int _tzjulian;
 
-time_t _systime(struct tm *);
-#endif
+extern int _daysmon[12];
 
+time_t _systime(struct tm *);
 void _tzset(void);
 int _daysyear(int);
 int _newyear(int);
-
-extern int _tzjulian;
-extern int _daysmon[12];
-extern char *_tzname[2];
+#endif
 
 extern unsigned _exitn;
 extern void (*_flushall)(void);
diff --git a/src/libc/time/localtime.c b/src/libc/time/localtime.c
@@ -7,7 +7,6 @@
 struct tzone {
         char *name;
         int gmtoff;
-        int isdst;
 };
 
 #include "tz.c"
@@ -17,6 +16,9 @@ gmtoff(char *tz)
 {
 	struct tzone *t;
 
+	if (!strcmp(tz, "UTC"))
+		return 0;
+
 	for (t = tzones; t->name; t++) {
 		if (!strcmp(t->name, tz))
 			return t->gmtoff;