From a034cceacdbe77694853524abce487a06937b016 Mon Sep 17 00:00:00 2001
From: JJenkx <josh_jenkins@hotmail.com>
Date: Thu, 22 Oct 2026 20:06:33 -0400
Subject: [PATCH] fix(libc): ignore the space and plus flags on wide unsigned
 conversions

The wide printf family passed its flags to the host for %o, %u, %x and
%X, and the UCRT honours a space flag on %u, so swprintf "% u" of 7
gave " 7". The libc.prx that titles ship applies the space and plus
flags to signed conversions only and gives "7". Drop them before the
host formats an unsigned conversion.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 core/libs/prx/libc/src/FormattingWide.cpp | 3 +++
 core/libs/tests/GuestWideFormatting.cpp   | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/core/libs/prx/libc/src/FormattingWide.cpp b/core/libs/prx/libc/src/FormattingWide.cpp
index a2b3d0fe7d..9f6dba530c 100644
--- a/core/libs/prx/libc/src/FormattingWide.cpp
+++ b/core/libs/prx/libc/src/FormattingWide.cpp
@@ -1,3 +1,4 @@
+#include <algorithm>
 #include <cerrno>
 #include <climits>
 #include <cstdint>
@@ -169,6 +170,8 @@ std::u16string FormatWide(const char16_t* format, VaList* source, bool secure =
             } else value = args.Next<unsigned long long>();
             if (conversion == u'o' && value == 0 && precision == 0 && spec.find('#') != std::string::npos)
                 spec = spec.substr(0, spec.find('.')) + ".1";
+            const auto flags = spec.begin() + static_cast<std::ptrdiff_t>(std::min(spec.find_first_not_of("-+ #0", 1), spec.size()));
+            spec.erase(std::remove_if(spec.begin() + 1, flags, [](char flag) { return flag == ' ' || flag == '+'; }), flags);
             AppendNumber(out, spec + "ll" + static_cast<char>(conversion), value);
         } else if (In(conversion, "aAeEfFgG")) {
             if (length == "L") AppendNumber(out, spec + "L" + static_cast<char>(conversion), args.Next<long double>());
diff --git a/core/libs/tests/GuestWideFormatting.cpp b/core/libs/tests/GuestWideFormatting.cpp
index 8ebfa2753e..7a1552e9c7 100644
--- a/core/libs/tests/GuestWideFormatting.cpp
+++ b/core/libs/tests/GuestWideFormatting.cpp
@@ -146,6 +146,12 @@ static void CheckCount() {
     Require(Format(buffer, 16, u"a%n", nullCount) < 0, "vswprintf null %n argument");
 }
 
+static void CheckUnsignedSignFlags() {
+    char16_t buffer[32];
+    Require(swprintf_nid_postfix(buffer, 32, u"[% u|%+u|% lu|% 5u|%+x|% #o]", 7u, 7u, 7ul, 7u, 7u, 7u) == 18 &&
+        buffer == std::u16string(u"[7|7|7|    7|7|07]"), "unsigned conversions ignore the space and plus flags");
+}
+
 static void CheckGroupingFlag() {
     char16_t buffer[48];
     Require(swprintf_nid_postfix(buffer, 48, u"%'d|%'-6u|%'.2f|%'+05d|%'g", 1234567, 42u, 1234.5, 12, 1e6) == 34 &&
@@ -322,4 +328,5 @@ int main() {
     Check(u"%.1s", "\xf0\x9f\x98\x80x", u"");
     Check(u"%.3s", "\xf0\x9f\x98\x80x", u"\U0001f600x");
     CheckGroupingFlag();
+    CheckUnsignedSignFlags();
 }