fix(libc): keep %% at end of input an input failure in the wide scanner

Co-Authored-By: Claude <[email protected]>

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

@@ -304,6 +304,7 @@ private:
         if (*format == u'%') {
             ++format;
             SkipSpace();
+            if (input.Peek() < 0) return Outcome::Input;
             return Literal(u'%');
         }
         const Directive directive = Parse();

core/libs/tests/GuestWideConversion.cpp

@@ -147,6 +147,7 @@ static void CheckScan() {
 
     Require(swscanf_s_nid_postfix(u"a", u"b%d", &first) == 0, "literal mismatch is a matching failure");
     Require(swscanf_s_nid_postfix(u"", u"x") == 0, "literal at end of input returns zero");
+    Require(swscanf_s_nid_postfix(u"", u"%%") == -1, "percent literal at end of input is an input failure");
     Require(swscanf_s_nid_postfix(u"", u"%d", &first) == -1, "empty input is an input failure");
     Require(swscanf_s_nid_postfix(u"   ", u"%ls", text, std::size_t{6}) == -1, "white space only is an input failure");
     Require(swscanf_s_nid_postfix(u"5", u"%d%d", &first, &second) == 1, "input failure after a conversion");
@@ -212,6 +213,7 @@ static void CheckUnsizedScan() {
 
     Require(swscanf_nid_postfix(u"a", u"b%d", &first) == 0, "swscanf literal mismatch is a matching failure");
     Require(swscanf_nid_postfix(u"", u"x") == 0, "swscanf literal at end of input returns zero");
+    Require(swscanf_nid_postfix(u"", u"%%") == -1, "swscanf percent literal at end of input is an input failure");
     Require(swscanf_nid_postfix(u"3 x", u"%d%d", &first, &second) == 1 && first == 3, "swscanf partial match");
     Require(swscanf_nid_postfix(u"", u"%d", &first) == -1, "swscanf empty input is an input failure");
     Require(swscanf_nid_postfix(u"", u"%ls", text) == -1, "swscanf empty input before %ls");

core/libs/tests/GuestWideStreamScan.cpp

@@ -105,6 +105,10 @@ static void CheckConsumption() {
     Require(ScanStream(stream, u"x") == 0, "a literal at end of input returns zero");
     Close(stream);
 
+    stream = Open("");
+    Require(ScanStream(stream, u"%%") == -1, "a percent literal at end of input is an input failure");
+    Close(stream);
+
     stream = Open("x");
     Require(ScanStream(stream, u"%d", &value) == 0, "a letter is not an integer");
     Require(fgetwc_nid_postfix(stream) == u'x', "the rejected letter is pushed back");

docs/dev/debt/libc.md

@@ -126,7 +126,7 @@
 - [syslog](../../../core/libs/prx/libc/src/Syslog.cpp) (libc) writes each message to `stderr` as `[syslog:<priority>] <message>`, with a newline added when missing, instead of sending it to the console's system log. Priority and facility handling follow FreeBSD's `vsyslog`: `%m` expands to the guest errno's message, unknown bits are reported (as priority 0x23, since FreeBSD passes `LOG_ERR|LOG_CONS|LOG_PERROR|LOG_PID` as the priority) and masked, a missing facility becomes `LOG_USER` or the facility set by `openlog`, and errno is preserved. `openlog` applies its identity and `LOG_PID`; a null identity retains the previous one, and a valid nonzero facility replaces the default. `closelog` clears the identity but retains the options and facility, as in FreeBSD 11; when no identity is set, FreeBSD falls back to the program name, which this backend does not emit. `LOG_PERROR` has no extra effect because stderr is the emulated log sink; `LOG_NDELAY`/`LOG_ODELAY`, `LOG_NOWAIT` and `LOG_CONS` have no daemon, child or console backend to control. `setlogmask` follows [FreeBSD 11](https://github.com/freebsd/freebsd-src/blob/8d2708de5d6112a492744d367cfdfb8fd219227a/lib/libc/gen/syslog.c): the process-wide mask defaults to 0xff, zero queries it, and nonzero values replace it; masked messages are skipped before formatting, including the unknown-priority diagnostic. The console's mask behaviour is unverified
 - [fwscanf, vfwscanf, wscanf, vwscanf and their `_s` forms](../../../core/libs/prx/libc/src/ScanningWide.cpp) (libc) run the `swscanf` scanner on characters read with `fgetwc`, so everything listed for `swscanf` in this file applies to them. As in the console's `libc.prx`, a field takes characters while they can still begin a valid item, so a failed field such as `0x` for `%x` stays consumed, and only the character that ended the scan goes back to the stream. That character is pushed back as its UTF-8 bytes with `ungetc`, because `ungetwc` takes single bytes only; the Windows C runtime guarantees one byte of push-back, so a non-ASCII lookahead can be lost there. A null stream or format returns `EOF`; the console checks them only in the `_s` forms.
 - [daemon](../../../core/libs/prx/libc/src/Process.cpp) (libc) throws: forking into the background is not supported. PPSA85300 imports it and fails to load without it. VLC 3.0 calls it only when its `daemon` option is set ([libvlc.c](https://github.com/videolan/vlc/blob/6de05adcbaf2e8b85fe86aad4169393098628119/src/libvlc.c#L190-L197)), and the title starts libVLC with `--ignore-config` and without `--daemon` ([player.cc](https://github.com/ZiZc3/VLC/blob/f3253020a64368153233ede29183014c0b6c8979/src/player.cc#L960-L981))
-- [_WStoul](../../../core/libs/prx/libc/src/Strings.cpp), [_Iswctype](../../../core/libs/prx/libc/src/RuneLocale.cpp), [swscanf_s and swscanf](../../../core/libs/prx/libc/src/ScanningWide.cpp) (libc) - `_WStoul` is `wcstoul` and throws for a base other than 0 or 2 to 36. `_Iswctype` takes the class numbers of Dinkumware's [xwcc.h](https://github.com/superna9999/ti-cgt6x/blob/cgt6x_7_3_4/include/xwcc.h) (1 `alnum` to 11 `xdigit`, 12 `blank`) and throws for any other value, including the FreeBSD masks `wctype` returns; the numbering is not confirmed on the console's `libc.prx`. `swscanf_s` follows C11 7.29.2.2 and K.3.9.1.5, but reads the size argument as `unsigned int` like `sscanf_s` where K.3.9.1.5 specifies `rsize_t`; the console's width is unverified. A runtime-constraint violation (null buffer, format or receiving pointer) only returns `EOF`, and a too small array gets a null first element as in `sscanf_s`. A literal at end of input returns the number of assignments, including zero, rather than `EOF`. An incomplete floating exponent such as `1e+` converts its mantissa, as reported from the console scanner in #8479; other incomplete exponent forms are not separately verified. A short `%c` field is currently a matching failure without storing its available prefix, while #9321 reports that the console stores a short `%3lc` field; its return count, partial-output extent and precedence are unverified. An integer field that is only a prefix, such as `0x`, does not convert; FreeBSD's `vfwscanf` reports an input failure for it. Integers out of range are truncated from `strtoll`/`strtoull`. `%p` follows FreeBSD 11's [vfwscanf.c](https://github.com/freebsd/freebsd-src/blob/4ab2e064d7950be84256d671a7ae93f87cc6aa36/lib/libc/stdio/vfwscanf.c#L610-L615): a hexadecimal integer with an optional `0x`, converted as unsigned and stored as a pointer; a length modifier on it throws, where FreeBSD ignores it. It throws for `%S`, `%C`, unknown length modifiers, scanset ranges, `%n` with suppression or width, and narrow `%s`, `%c` or `%[` input that the C-locale `wcrtomb` cannot convert. `swscanf` runs the same scanner without the size arguments of `%s`, `%c` and `%[`, as FreeBSD's [swscanf.c](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/lib/libc/stdio/swscanf.c) passes its arguments to `vswscanf`, so everything above except the sizes applies to it; it also keeps the null buffer, format and receiving pointer checks returning `EOF`, where C leaves those undefined. Neither variant is confirmed on a PS5 title
+- [_WStoul](../../../core/libs/prx/libc/src/Strings.cpp), [_Iswctype](../../../core/libs/prx/libc/src/RuneLocale.cpp), [swscanf_s and swscanf](../../../core/libs/prx/libc/src/ScanningWide.cpp) (libc) - `_WStoul` is `wcstoul` and throws for a base other than 0 or 2 to 36. `_Iswctype` takes the class numbers of Dinkumware's [xwcc.h](https://github.com/superna9999/ti-cgt6x/blob/cgt6x_7_3_4/include/xwcc.h) (1 `alnum` to 11 `xdigit`, 12 `blank`) and throws for any other value, including the FreeBSD masks `wctype` returns; the numbering is not confirmed on the console's `libc.prx`. `swscanf_s` follows C11 7.29.2.2 and K.3.9.1.5, but reads the size argument as `unsigned int` like `sscanf_s` where K.3.9.1.5 specifies `rsize_t`; the console's width is unverified. A runtime-constraint violation (null buffer, format or receiving pointer) only returns `EOF`, and a too small array gets a null first element as in `sscanf_s`. A literal at end of input returns the number of assignments, including zero, rather than `EOF` as FreeBSD does, as reported from the console scanner in #8479; `%%` at end of input still returns `EOF`. A literal mismatch is a matching failure, where FreeBSD's `vfwscanf` reports an input failure. An incomplete floating exponent such as `1e+` converts its mantissa, as reported from the console scanner in #8479; other incomplete exponent forms are not separately verified. A short `%c` field is currently a matching failure without storing its available prefix, while #9321 reports that the console stores a short `%3lc` field; its return count, partial-output extent and precedence are unverified. An integer field that is only a prefix, such as `0x`, does not convert; FreeBSD's `vfwscanf` pushes back the `x` and converts the `0`. Integers out of range are truncated from `strtoll`/`strtoull`. `%p` follows FreeBSD 11's [vfwscanf.c](https://github.com/freebsd/freebsd-src/blob/4ab2e064d7950be84256d671a7ae93f87cc6aa36/lib/libc/stdio/vfwscanf.c#L610-L615): a hexadecimal integer with an optional `0x`, converted as unsigned and stored as a pointer; a length modifier on it throws, where FreeBSD ignores it. It throws for `%S`, `%C`, unknown length modifiers, scanset ranges, `%n` with suppression or width, and narrow `%s`, `%c` or `%[` input that the C-locale `wcrtomb` cannot convert. `swscanf` runs the same scanner without the size arguments of `%s`, `%c` and `%[`, as FreeBSD's [swscanf.c](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/lib/libc/stdio/swscanf.c) passes its arguments to `vswscanf`, so everything above except the sizes applies to it; it also keeps the null buffer, format and receiving pointer checks returning `EOF`, where C leaves those undefined. Neither variant is confirmed on a PS5 title
 - [flock](../../../core/libs/prx/libc/src/FileLock.cpp) (libkernel) on Windows shares one lock state between duplicated descriptors, following FreeBSD 11.4's [flock(2)](https://github.com/freebsd/freebsd-src/blob/releng/11.4/lib/libc/sys/flock.2). Independent opens have separate states; closing a descriptor or reopening a stream drops only its reference. Lock transitions on one open file description are serialized. The lock is a host [LockFileEx](https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-lockfileex) lock on one byte at offset 2^63 - 2, which no file reaches, so it excludes other `flock` calls and leaves reads, writes and mapped views alone, like FreeBSD's advisory locks. Console behavior, signal interruption and concurrent closure of a descriptor while its lock call is pending are unverified.
 - [std::_Throw_Cpp_error](../../../core/libs/prx/libc/src/exception/StandardExceptions.cpp) (libc) follows Dinkumware `thread0.cpp` ([VC12](https://github.com/ganboing/crt.vc12/blob/f1d47126/src/thread0.cpp), [STL](https://github.com/microsoft/STL/blob/da52dc0f/stl/src/thread0.cpp)), without console verification. Codes outside 0..6 throw `std::out_of_range`, the deleting destructor throws, and STREAMS errnos absent from FreeBSD 11.4 [`errno.h`](https://github.com/freebsd/freebsd-src/blob/releng/11.4/sys/sys/errno.h) (`ENODATA`, `ENOSR`, `ENOSTR`, `ETIME`) are omitted. Codes 0..6 throw a 32-byte [VC12 `system_error`](https://github.com/ganboing/crt.vc12/blob/f1d47126/src/system_error) with FreeBSD errnos (16, 22, 3, 12, 1, 11, 35), a static `generic_category` (not `_Generic_object`), and unverified 40-byte [GuestLocale::String](../../../core/libs/prx/libc/include/GuestLocale.hpp) messages from [`syserror.cpp`](https://github.com/ganboing/crt.vc12/blob/f1d47126/src/syserror.cpp)
 - [Call tracing](../../../core/libs/prx/libc/src/specifics/x86_64/CallTrace.cpp) (`--trace-imports`, `APS5_TRACE_CALLS`) is missing on macOS and records only the entry of a call, not its arguments or result. One process-wide ring keeps the last 65536 calls, so a busy thread pushes the others out; the reporting thread's own calls are listed only while they are still in that ring. Calls are counted per traced target; an import bound to a target already traced under another name is counted under the first name. The thunk saves the integer argument registers and `xmm0` to `xmm7`; wider vector arguments survive only while the recording code avoids AVX, which is untested. Linux has no crash report, so it prints the trace only on `SIGABRT` (guest or host `abort()`), not on `SIGSEGV`; a caller in a module loaded after the last traced import prints without a module name, and a thread aborting while another writes the report waits for it at most 2 seconds