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Fix strftime if tm_zone is null.

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Upstream tzcode said "On platforms with tm_zone, strftime.c now assumes it
is not NULL". Which is fine for any struct tm generated by tzcode, but not
necessarily true of a struct tm constructed by arbitrary code. In particular,
Netflix on Nexus Player was failing to start because they format "%Z" with
a struct tm whose tm_zone is null (the other fields are valid, but, yeah,
that's probably not intentional).

glibc takes a null tm_zone to mean "the current time zone", so let's do that
too. (Historically Android would use the empty string, and POSIX doesn't
clarify which of this is the appropriate behavior when tm_zone is null.)

Bug: http://b/25170306
Change-Id: Idbf68bfe90d143aca7dada8607742905188b1d33
This commit is contained in:
Elliott Hughes
2015-11-12 16:51:31 -08:00
parent 7c10ee9473
commit a9cac4c87a
3 changed files with 58 additions and 1 deletions
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38
tests/time_test.cpp
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@@ -143,6 +143,44 @@ TEST(time, strftime) {
EXPECT_STREQ("Sun Mar 10 00:00:00 2100", buf);
}
TEST(time, strftime_null_tm_zone) {
// Netflix on Nexus Player wouldn't start (http://b/25170306).
struct tm t;
memset(&t, 0, sizeof(tm));
char buf[64];
setenv("TZ", "America/Los_Angeles", 1);
tzset();
t.tm_isdst = 0; // "0 if Daylight Savings Time is not in effect".
EXPECT_EQ(5U, strftime(buf, sizeof(buf), "<%Z>", &t));
EXPECT_STREQ("<PST>", buf);
#if defined(__BIONIC__) // glibc 2.19 only copes with tm_isdst being 0 and 1.
t.tm_isdst = 2; // "positive if Daylight Savings Time is in effect"
EXPECT_EQ(5U, strftime(buf, sizeof(buf), "<%Z>", &t));
EXPECT_STREQ("<PDT>", buf);
t.tm_isdst = -123; // "and negative if the information is not available".
EXPECT_EQ(2U, strftime(buf, sizeof(buf), "<%Z>", &t));
EXPECT_STREQ("<>", buf);
#endif
setenv("TZ", "UTC", 1);
tzset();
t.tm_isdst = 0;
EXPECT_EQ(5U, strftime(buf, sizeof(buf), "<%Z>", &t));
EXPECT_STREQ("<UTC>", buf);
#if defined(__BIONIC__) // glibc 2.19 thinks UTC DST is "UTC".
t.tm_isdst = 1; // UTC has no DST.
EXPECT_EQ(2U, strftime(buf, sizeof(buf), "<%Z>", &t));
EXPECT_STREQ("<>", buf);
#endif
}
TEST(time, strptime) {
setenv("TZ", "UTC", 1);