feat(libc): export tzname

ES-DE in RetroArch (PPSA99169) imports tzname from libSceLibcInternal and
fails to load without it; ICU's uprv_tzname reads it after localtime. It
points at the host's zone names and tzset refreshes it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/libs/prx/libc/src/Time.cpp

@@ -402,10 +402,22 @@ std::size_t formatGuestTime(char* destination, std::size_t size, const char* for
     *buffer.cursor = '\0';
     return static_cast<std::size_t>(buffer.cursor - destination);
 }
+
+char** HostZoneNames() {
+#ifdef _WIN32
+    _tzset();
+    return _tzname;
+#else
+    ::tzset();
+    return ::tzname;
+#endif
+}
 }
 
 extern "C" {
 
+char* tzname_nid_postfix[2] = {HostZoneNames()[0], HostZoneNames()[1]};
+
 GuestTm* APS5_VABI localtime_s_nid_postfix(const int64_t* timer, GuestTm* result);
 GuestTm* APS5_VABI gmtime_s_nid_postfix(const int64_t* timer, GuestTm* result);
 std::size_t APS5_VABI wcsrtombs_nid_postfix(char* destination, const std::uint16_t** source, std::size_t capacity, void* state);
@@ -413,11 +425,9 @@ std::size_t APS5_VABI mbsrtowcs_nid_postfix(std::uint16_t* destination, const ch
 int APS5_VABI ___mb_cur_max_nid_postfix();
 
 void APS5_VABI tzset_nid_postfix(void) {
-#ifdef _WIN32
-    _tzset();
-#else
-    ::tzset();
-#endif
+    char** names = HostZoneNames();
+    tzname_nid_postfix[0] = names[0];
+    tzname_nid_postfix[1] = names[1];
 }
 
 int64_t APS5_VABI libc_time_nid_postfix(int64_t* timer) {

core/libs/tests/GuestTimeConversion.cpp

@@ -23,6 +23,7 @@ char* APS5_VABI asctime_nid_postfix(const GuestTm*);
 std::int64_t APS5_VABI mktime_nid_postfix(GuestTm*);
 std::size_t APS5_VABI strftime_nid_postfix(char*, std::size_t, const char*, const GuestTm*);
 void APS5_VABI tzset_nid_postfix(void);
+extern char* tzname_nid_postfix[2];
 char* APS5_VABI ctime_nid_postfix(const std::int64_t*);
 int* APS5_VABI __error_nid_postfix();
 double APS5_VABI libc_difftime_nid_postfix(std::int64_t, std::int64_t);
@@ -388,4 +389,14 @@ int main() {
     GuestTm shifted{};
     Require(localtime_s_nid_postfix(&epoch, &shifted) == &shifted && shifted.tm_hour == 5 && shifted.tm_gmtoff == 18000,
         "tzset did not pick up the new TZ");
+    Require(tzname_nid_postfix[0] != nullptr && std::strcmp(tzname_nid_postfix[0], "UTC") == 0 && tzname_nid_postfix[1] != nullptr,
+        "tzname does not name the zone tzset set");
+#ifdef _WIN32
+    _putenv_s("TZ", "EST5EDT");
+#else
+    setenv("TZ", "EST5EDT", 1);
+#endif
+    tzset_nid_postfix();
+    Require(std::strcmp(tzname_nid_postfix[0], "EST") == 0 && std::strcmp(tzname_nid_postfix[1], "EDT") == 0,
+        "tzname does not name the standard and daylight zones");
 }

docs/dev/debt/libc.md

@@ -55,6 +55,7 @@
 - [The scanf family](../../../core/libs/prx/libc/src/Formatting.cpp) (libc), the `_s` forms included, on Linux throws for the 16-bit wide conversions (`%ls`, `%lc`, `%l[`, `%S`, `%C`): glibc would store a 32-bit `wchar_t` per character into the guest's 16-bit buffer. Windows hands `%ls`, `%lc` and `%l[` to the host, whose `wchar_t` is 16 bits
 - [The scanf family](../../../core/libs/prx/libc/include/WindowsScanning.hpp) (libc) on Windows returns 0, as C17 and FreeBSD do, when input fails after only suppressed conversions have completed (`sscanf("12", "%*d%d", &value)`). Linux hands the format to glibc, which returns `EOF` there. On Windows the host stops a `%x`, `%X`, `%i` or `%p` after the `x` of a `0x` that no hex digit follows (or that the width cuts off), and a float conversion (`%e`, `%f`, `%g`, `%a`) after the `e` of an exponent with no digits (`1e`), where C17 and FreeBSD stop before the `x` or the `e`
 - [Guest path resolution](../../../core/libs/prx/libc/src/General.cpp) falls back to ASCII case-insensitive component lookup, following [shadPS4's host filesystem](https://github.com/shadps4-emu/shadPS4/blob/945dbc3cc3eee80ac3e053b438502ed936fa6bb2/src/core/file_sys/backends/host_fs.cpp). PPSA03747 requests `Skyrim.INI`, `Data/Video` and lowercase archive/plugin names that differ from the dump's filenames. Exact host names take precedence; multiple fallback matches throw instead of selecting an arbitrary file. Existing parent names are resolved when creating a new file, and guest mount aliases use the same ASCII comparison. Results are not cached, so renames and newly created files remain visible. Unicode case folding and PS5 behaviour for case-colliding host entries are unverified; host roots are used as supplied. Explicit native Windows drive and UNC paths bypass guest parent-component validation.
+- [tzname](../../../core/libs/prx/libc/src/Time.cpp) (libc) points at the host's zone names, read at load and again by `tzset`: the abbreviations a `TZ` string gives (`EST5EDT` is `EST` and `EDT` on both hosts), but on Windows without `TZ` the CRT's full names such as `GMT Standard Time`, which ICU's [uprv_tzname](https://github.com/unicode-org/icu/blob/457157a92aa053e632cc7fcfd0e12f8a943b2d11/icu4c/source/common/putil.cpp#L1244-L1264) (ES-DE in PPSA99169) cannot map to a zone ID. A zone with no daylight-saving time has `tzname[1]` empty on Windows and equal to `tzname[0]` on Linux, where FreeBSD leaves three spaces. The console's names are not known
 - [localtime, mktime](../../../core/libs/prx/libc/src/Time.cpp) (libc) on Windows convert through the CRT's `localtime_s` and `mktime`, which accept about 1970 to January 3001 UTC and apply the CRT's daylight-saving rule. A time outside that range is converted a whole number of 400-year Gregorian cycles away, where the calendar repeats, so it gets the rule the CRT applies to that year and not the zone's historical one. `gmtime` converts every time whose year fits an `int` on both hosts.
 - [strftime and asctime](../../../core/libs/prx/libc/src/Time.cpp) (libc) follow FreeBSD 11 [strftime.c](https://github.com/freebsd/freebsd-src/blob/5ed7eb0d97ba4436218e810f61bd059acba984c2/lib/libc/stdtime/strftime.c) and [asctime.c](https://github.com/freebsd/freebsd-src/blob/5ed7eb0d97ba4436218e810f61bd059acba984c2/contrib/tzcode/stdtime/asctime.c) with the C locale on every host, not measured on the console; other locales are not implemented. `%s` follows FreeBSD 9 and 11 and is the local-time `mktime` of the broken-down time (current FreeBSD uses `tm_gmtoff`), which is -1 on Windows outside the range above. `%Z` is `tm_zone`, or `tzname[tm_isdst != 0]` when it is null and `tm_isdst` is not negative. The two-digit year warning FreeBSD writes to `stderr` when `CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS` is set is not written
 - [wcsftime](../../../core/libs/prx/libc/src/Time.cpp) (libc) follows FreeBSD 11.4's [wcsftime.c](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/lib/libc/locale/wcsftime.c) over this library's `wcsrtombs`, `strftime` and `mbsrtowcs` in the single-byte C locale of [none.c](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/lib/libc/locale/none.c), with the guest's 16-bit `wchar_t`, without console verification. It has the `strftime` gaps above. A format unit above 255 returns 0 with `EILSEQ`; an empty result, a result that does not fit and a null buffer return 0 with `errno` unchanged, discarding the `ERANGE` or `EINVAL` that the Windows CRT's `strftime` sets. A null format or `tm` throws, where FreeBSD dereferences it (a null `tm` is read there only when the format has a conversion that needs it)