fix(libc): return invalid argument error on null buffer in basename_r

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

@@ -30,7 +30,10 @@ long long APS5_VABI strtonum_nid_postfix(const char* text, long long minimum, lo
 }
 
 char* APS5_VABI basename_r_nid_postfix(const char* path, char* buffer) {
-    if (buffer == nullptr) throw std::invalid_argument("basename_r: null buffer");
+    if (buffer == nullptr) {
+        errno = 22;
+        return nullptr;
+    }
     std::string_view name = path && *path ? path : ".";
     while (name.size() > 1 && name.back() == '/') name.remove_suffix(1);
     if (name != "/") {

core/libs/tests/GuestStrings.cpp

@@ -379,6 +379,8 @@ int main() {
     Require(basename_r_nid_postfix(("/a/" + longest).c_str(), baseBuffer) == baseBuffer && std::strlen(baseBuffer) == 1023);
     *__error_nid_postfix() = 0;
     Require(basename_r_nid_postfix(longName.c_str(), baseBuffer) == nullptr && *__error_nid_postfix() == 63);
+    *__error_nid_postfix() = 0;
+    Require(basename_r_nid_postfix(path, nullptr) == nullptr && *__error_nid_postfix() == 22);
     const unsigned char loopbackBytes[4] = {127, 0, 0, 1};
     unsigned int loopback;
     std::memcpy(&loopback, loopbackBytes, sizeof(loopback));

docs/dev/debt/libc.md

@@ -43,6 +43,7 @@
 - [getw and putw](../../../core/libs/prx/libc/src/BinaryWordIo.cpp) (libc) follow FreeBSD 11.4 [getw.c](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/lib/libc/stdio/getw.c) and [putw.c](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/lib/libc/stdio/putw.c): one 32-bit little-endian word, `getw` returns -1 for EOF or an error, and `putw` returns 0 on success or -1 on error while holding the stream lock. They use the existing host-backed streams, so buffering and error timing follow the host CRT. Null streams throw and closed streams return -1 with `EBADF`, as existing byte I/O does. Console behavior is unverified.
 - [vsnwprintf_s](../../../core/libs/prx/libc/src/FormattingWide.cpp) (libc) - `va_list` counterpart of `snwprintf_s` (C11 K.3.9.1.3): truncates to the buffer and returns the full length, with the same constraints and argument checks
 - [strndup and strdup](../../../core/libs/prx/libc/src/AllocatingStrings.cpp) (libc) return null with `errno` set to `EINVAL` (22) when `source` is null, preventing a host segfault on invalid guest input. POSIX.1-2008 and FreeBSD 11.4 libc leave `strndup(NULL)` and `strdup(NULL)` undefined (faulting); exact console behavior on hardware is unverified.
+- [basename_r](../../../core/libs/prx/libc/src/StringExtensions.cpp) (libc) returns null with `errno` set to `EINVAL` (22) when `buffer` is null, following POSIX reentrant conventions and preventing an unhandled crash on invalid guest input. Exact console behavior on hardware is unverified.
 - [snprintf_s and vsnprintf_s](../../../core/libs/prx/libc/src/Formatting.cpp) (libc) - follow C11 K.3.5.3.5 and K.3.5.3.12 with `RSIZE_MAX` assumed to be `SIZE_MAX >> 1`, as `snwprintf_s` does: a null buffer or format, `size` of 0 or above `RSIZE_MAX`, any `%n` and a null `%s`, `%ls` or `%S` argument return a negative value and set `buffer[0]` to zero when the buffer and size allow it; otherwise the output is truncated to the buffer and the full length is returned. A violation only returns: the constraint handler is not invoked, and the console's error value is unverified. Not confirmed on a PS5 title
 - [vsscanf_s](../../../core/libs/prx/libc/src/Formatting.cpp) (libc) - returns the count of items converted before an undersized `%s`/`%c`/`%[` destination (0 when it is the first), not EOF. Not confirmed on a PS5 title
 - [localeconv](../../../core/libs/prx/libc/src/LocaleSupport.cpp) (libc, re-exported by libSceAmpr) - the 0x90-byte Dinkumware struct (empty monetary strings, `CHAR_MAX` for the 14 `char` fields, `decimal_point` ".", `_False`/`_True` "false"/"true") is read from the `libc.prx` that Astro's Playroom ships. It is a fixed C-locale table: whether the console changes it with `setlocale` is not known, and `_Frac_grouping`, `_Frac_sep`, `_No`, `_Yes` are empty strings as in that dump