RedBear-OS/recipes/wip/qt/qtbase/redox.patch

diff -ruwN source-old/cmake/QtPlatformSupport.cmake source/cmake/QtPlatformSupport.cmake
--- source-old/cmake/QtPlatformSupport.cmake	2024-12-02 05:39:06.000000000 +0000
+++ source/cmake/QtPlatformSupport.cmake	2026-04-13 00:00:00.000000000 +0000
@@ -55,8 +55,20 @@
     set(NETBSD 0)
 endif()
 
+# REDOX is set by the Redox toolchain file (redox-toolchain.cmake) as CACHE INTERNAL.
+# When CMAKE_SYSTEM_NAME is "Linux" (for CMake UNIX detection), we need this variable
+# to enable Redox-specific code paths (mkspec, QPA plugin, platform tweaks).
+# Falls back to checking CMAKE_SYSTEM_NAME for standalone/non-toolchain usage.
+if(NOT DEFINED REDOX)
+    if(CMAKE_SYSTEM_NAME STREQUAL "Redox")
+        set(REDOX 1)
+    else()
+        set(REDOX 0)
+    endif()
+endif()
+
 if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten" OR EMSCRIPTEN)
     set(WASM 1)
 else()
     set(WASM 0)
 endif()
 diff -ruwN source-old/cmake/QtMkspecHelpers.cmake source/cmake/QtMkspecHelpers.cmake
--- source-old/cmake/QtMkspecHelpers.cmake	2024-12-02 05:39:06.000000000 +0000
+++ source/cmake/QtMkspecHelpers.cmake	2026-04-13 00:00:00.000000000 +0000
@@ -46,4 +46,8 @@
         endif()
+    elseif(REDOX)
+        if(GCC)
+            set(QT_DEFAULT_MKSPEC redox-g++)
+        endif()
     elseif(LINUX)
         if(GCC)
             set(QT_DEFAULT_MKSPEC linux-g++)
diff -ruwN /dev/null source/mkspecs/redox-g++/qmake.conf
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/mkspecs/redox-g++/qmake.conf	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,14 @@
+#
+# qmake configuration for redox-g++
+#
+
+MAKEFILE_GENERATOR      = UNIX
+QMAKE_PLATFORM         += redox
+CONFIG                 += incremental
+QMAKE_INCREMENTAL_STYLE = sublib
+
+include(../common/unix.conf)
+include(../common/gcc-base-unix.conf)
+include(../common/g++-unix.conf)
+
+load(qt_config)
diff -ruwN /dev/null source/mkspecs/redox-g++/qplatformdefs.h
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/mkspecs/redox-g++/qplatformdefs.h	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,27 @@
+// Copyright (C) 2026 Red Bear OS contributors
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QPLATFORMDEFS_H
+#define QPLATFORMDEFS_H
+
+#include "qglobal.h"
+
+#include <unistd.h>
+
+#include <dirent.h>
+#include <fcntl.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+
+#ifndef O_LARGEFILE
+#  define O_LARGEFILE 0
+#endif
+
+#include "../common/posix/qplatformdefs.h"
+
+#define QT_SNPRINTF ::snprintf
+#define QT_VSNPRINTF ::vsnprintf
+
+#endif // QPLATFORMDEFS_H
diff -ruwN /dev/null source/src/corelib/private/qcore_unix_p.h
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/corelib/private/qcore_unix_p.h	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "../kernel/qcore_unix_p.h"
+
diff -ruwN /dev/null source/src/corelib/private/qeventdispatcher_unix_p.h
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/corelib/private/qeventdispatcher_unix_p.h	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "../kernel/qeventdispatcher_unix_p.h"
+
diff -ruwN /dev/null source/src/corelib/private/qtimerinfo_unix_p.h
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/corelib/private/qtimerinfo_unix_p.h	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "../kernel/qtimerinfo_unix_p.h"
+
diff -ruwN source-old/src/corelib/global/qsystemdetection.h source/src/corelib/global/qsystemdetection.h
--- source-old/src/corelib/global/qsystemdetection.h	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/global/qsystemdetection.h	2026-04-13 00:00:00.000000000 +0000
@@ -30,6 +30,7 @@
      HURD     - GNU Hurd
      QNX      - QNX [has variants]
      QNX6     - QNX RTP 6.1
+     REDOX    - Redox OS
      LYNX     - LynxOS
      BSD4     - Any BSD 4.4 system
      UNIX     - Any UNIX BSD/SYSV system
@@ -123,6 +124,8 @@
 #  define Q_OS_VXWORKS
 #elif defined(__HAIKU__)
 #  define Q_OS_HAIKU
+#elif defined(__redox__)
+#  define Q_OS_REDOX
 #elif defined(__MAKEDEPEND__)
 #else
 #  error "Qt has not been ported to this OS - see http://www.qt-project.org/"
diff -ruwN source-old/src/corelib/kernel/qcore_unix_p.h source/src/corelib/kernel/qcore_unix_p.h
--- source-old/src/corelib/kernel/qcore_unix_p.h	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/kernel/qcore_unix_p.h	2026-04-13 00:00:00.000000000 +0000
@@ -243,9 +243,15 @@
 #ifdef AT_FDCWD
 static inline int qt_safe_openat(int dfd, const char *pathname, int flags, mode_t mode = 0777)
 {
     // everyone already has O_CLOEXEC
     int fd;
+#ifdef Q_OS_REDOX
+    if (dfd != AT_FDCWD)
+        return -1;
+    QT_EINTR_LOOP(fd, QT_OPEN(pathname, flags | O_CLOEXEC, mode));
+#else
     QT_EINTR_LOOP(fd, openat(dfd, pathname, flags | O_CLOEXEC, mode));
+#endif
     return fd;
 }
 #endif
diff -ruwN source-old/src/gui/CMakeLists.txt source/src/gui/CMakeLists.txt
--- source-old/src/gui/CMakeLists.txt	2024-12-02 05:39:06.000000000 +0000
+++ source/src/gui/CMakeLists.txt	2026-04-13 00:00:00.000000000 +0000
@@ -20,6 +20,8 @@
         set(_default_platform "eglfs")
     elseif(HAIKU)
         set(_default_platform "haiku")
+    elseif(REDOX)
+        set(_default_platform "redox")
     elseif(WASM)
         set(_default_platform "wasm")
     else()
diff -ruwN source-old/src/plugins/platforms/CMakeLists.txt source/src/plugins/platforms/CMakeLists.txt
--- source-old/src/plugins/platforms/CMakeLists.txt	2024-12-02 05:39:06.000000000 +0000
+++ source/src/plugins/platforms/CMakeLists.txt	2026-04-13 00:00:00.000000000 +0000
@@ -22,6 +22,9 @@
 if(QNX)
     add_subdirectory(qnx)
 endif()
+if(REDOX)
+    add_subdirectory(redox)
+endif()
 if(QT_FEATURE_eglfs)
     add_subdirectory(eglfs)
     add_subdirectory(minimalegl)
diff -ruwN /dev/null source/src/plugins/platforms/redox/CMakeLists.txt
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/plugins/platforms/redox/CMakeLists.txt	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: BSD-3-Clause
+
+qt_internal_add_plugin(QRedoxIntegrationPlugin
+    OUTPUT_NAME qredox
+    PLUGIN_TYPE platforms
+    DEFAULT_IF "redox" IN_LIST QT_QPA_PLATFORMS
+    SOURCES
+        main.cpp
+    LIBRARIES
+        Qt::Core
+        Qt::CorePrivate
+        Qt::Gui
+        Qt::GuiPrivate
+)
diff -ruwN /dev/null source/src/plugins/platforms/redox/main.cpp
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/plugins/platforms/redox/main.cpp	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include <qpa/qplatformintegrationfactory_p.h>
+#include <qpa/qplatformintegrationplugin.h>
+
+QT_BEGIN_NAMESPACE
+
+class QRedoxIntegrationPlugin : public QPlatformIntegrationPlugin
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID QPlatformIntegrationFactoryInterface_iid FILE "redox.json")
+public:
+    QPlatformIntegration *create(const QString &system, const QStringList &paramList) override;
+};
+
+QPlatformIntegration *QRedoxIntegrationPlugin::create(const QString &system, const QStringList &paramList)
+{
+    if (system.compare(QStringLiteral("redox"), Qt::CaseInsensitive) != 0)
+        return nullptr;
+
+    int argc = 0;
+    char **argv = nullptr;
+    return QPlatformIntegrationFactory::create(QStringLiteral("wayland"), paramList, argc, argv);
+}
+
+QT_END_NAMESPACE
+
+#include "main.moc"
diff -ruwN /dev/null source/src/plugins/platforms/redox/redox.json
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/plugins/platforms/redox/redox.json	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,3 @@
+{
+    "Keys": [ "redox" ]
+}
diff -ruwN source-old/src/3rdparty/sha3/brg_endian.h source/src/3rdparty/sha3/brg_endian.h
--- source-old/src/3rdparty/sha3/brg_endian.h	2024-12-02 05:39:06.000000000 +0000
+++ source/src/3rdparty/sha3/brg_endian.h	2026-04-13 00:00:00.000000000 +0000
@@ -45,6 +45,8 @@
 #  if !defined( __MINGW32__ ) && !defined( _AIX ) && !defined(Q_OS_QNX)
 #    include <endian.h>
-#    if !defined( __BEOS__ ) && !defined(Q_OS_RTEMS) && !defined(Q_OS_VXWORKS)
+#    if defined(__redox__)
+      /* Redox: byteswap.h not in relibc, bswap from endian.h suffices */
+#    elif !defined( __BEOS__ ) && !defined(Q_OS_RTEMS) && !defined(Q_OS_VXWORKS)
 #      include <byteswap.h>
 #    endif
 #  endif
diff -ruwN source-old/src/corelib/io/qstorageinfo_unix.cpp source/src/corelib/io/qstorageinfo_unix.cpp
--- source-old/src/corelib/io/qstorageinfo_unix.cpp	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/io/qstorageinfo_unix.cpp	2026-04-13 00:00:00.000000000 +0000
@@ -51,7 +51,13 @@
 #  if !defined(_STATFS_F_FLAGS) && !defined(Q_OS_NETBSD)
 #    define _STATFS_F_FLAGS 1
 #  endif
-#elif defined(Q_OS_HAIKU) || defined(Q_OS_CYGWIN)
+#elif defined(Q_OS_REDOX)
+#  define QT_STATFSBUF struct statvfs
+#  define QT_STATFS    ::statvfs
+#  if !defined(ST_RDONLY)
+#    define ST_RDONLY 1
+#  endif
+#elif defined(Q_OS_HAIKU) || defined(Q_OS_CYGWIN)
 #  define QT_STATFSBUF struct statvfs
 #  define QT_STATFS    ::statvfs

diff -ruwN source-old/configure.cmake source/configure.cmake
--- source-old/configure.cmake	2024-12-02 05:39:06.000000000 +0000
+++ source/configure.cmake	2026-04-15 00:00:00.000000000 +0000
@@ -1233,7 +1233,7 @@
 qt_feature("intelcet" PRIVATE
     LABEL "Using Intel Control-flow Enforcement Technology (CET)"
     AUTODETECT ON
-    CONDITION TEST_intelcet
+    CONDITION TEST_intelcet AND NOT REDOX
 )
 qt_feature_config("intelcet" QMAKE_PUBLIC_CONFIG)
 qt_feature("glibc_fortify_source" PRIVATE
diff -ruwN source-old/cmake/QtBaseConfigureTests.cmake source/cmake/QtBaseConfigureTests.cmake
--- source-old/cmake/QtBaseConfigureTests.cmake	2024-12-02 05:39:06.000000000 +0000
+++ source/cmake/QtBaseConfigureTests.cmake	2026-04-16 00:00:00.000000000 +0000
@@ -265,4 +265,23 @@
     set(TEST_subarch_sse4_1 FALSE CACHE BOOL INTERNAL FORCE)
     set(TEST_subarch_sse4_2 FALSE CACHE BOOL INTERNAL FORCE)
 endif()
+if(REDOX)
+    set(QT_FEATURE_avx OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx2 OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_f16c OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512f OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512er OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512cd OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512pf OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512dq OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512bw OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512vl OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512ifma OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512vbmi OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_avx512vbmi2 OFF CACHE BOOL INTERNAL FORCE)
+    set(QT_FEATURE_vaes OFF CACHE BOOL INTERNAL FORCE)
+    set(TEST_subarch_avx FALSE CACHE BOOL INTERNAL FORCE)
+    set(TEST_subarch_avx2 FALSE CACHE BOOL INTERNAL FORCE)
+    set(TEST_subarch_avx512vbmi2 FALSE CACHE BOOL INTERNAL FORCE)
+endif()
 qt_run_qtbase_config_tests()

diff -ruwN source-old/src/corelib/plugin/qelfparser_p.cpp source/src/corelib/plugin/qelfparser_p.cpp
--- source-old/src/corelib/plugin/qelfparser_p.cpp	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/plugin/qelfparser_p.cpp	2026-04-15 00:00:00.000000000 +0000
@@ -177,5 +177,8 @@
     static bool checkElfVersion(const uchar *ident)
     {
+#ifdef Q_OS_REDOX
+        return true;
+#endif
         uchar elfversion = ident[EI_VERSION];
         return elfversion == EV_CURRENT;
     }
@@ -258,4 +261,7 @@
     static bool checkFileVersion(const Ehdr &header)
     {
+#ifdef Q_OS_REDOX
+        return true;
+#endif
         return header.e_version == EV_CURRENT;
     }

@@ -742,7 +752,9 @@

     qEDebug << ElfHeaderDebug{ reinterpret_cast<const uchar *>(data.data()) };

-    auto header = reinterpret_cast<const T::Ehdr *>(data.data());
+    typename T::Ehdr headerStorage;
+    memcpy(&headerStorage, data.data(), sizeof(headerStorage));
+    const auto header = &headerStorage;
     if (!ElfHeaderCheck<>::checkHeader(*header))
         return error(ElfHeaderCheck<>::explainCheckFailure(*header));

diff -ruwN source-old/src/corelib/plugin/qlibrary.cpp source/src/corelib/plugin/qlibrary.cpp
--- source-old/src/corelib/plugin/qlibrary.cpp	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/plugin/qlibrary.cpp	2026-04-19 00:00:00.000000000 +0000
@@ -17,6 +17,10 @@
 #include <qoperatingsystemversion.h>
 #include <qstringlist.h>
 
+#ifdef Q_OS_REDOX
+#  include <unistd.h>
+#endif
+
 #ifdef Q_OS_DARWIN
 #  include <private/qcore_mac_p.h>
 #endif
@@ -176,7 +180,14 @@
      to it being used in the plugin in the first place.
    */
 #if defined(Q_OF_ELF)
+#  if defined(Q_OS_REDOX)
+    // Redox currently reaches the plugin file successfully but the ELF-specific
+    // metadata parser misreads shared plugins inside the guest runtime. Fall
+    // back to the generic QTMETADATA search path until the Redox ELF loader /
+    // parser path is trustworthy again.
+#  else
     return QElfParser::parse({s, s_len}, errMsg);
+#  endif
 #elif defined(Q_OF_MACH_O)
     return QMachOParser::parse(s, s_len, errMsg);
 #elif defined(Q_OS_WIN) || defined(Q_OS_CYGWIN)
 @@ -230,7 +234,41 @@
              Q_INT64_C(1) << (sizeof(qsizetype) > 4 ? 40 : 29);
 
     qsizetype fdlen = qMin(file.size(), MaxMemoryMapSize);
-    const char *filedata = reinterpret_cast<char *>(file.map(0, fdlen));
+    const char *filedata = nullptr;
+    QByteArray data;
+
+#ifdef Q_OS_REDOX
+    const qsizetype readLimit = qMin<qsizetype>(fdlen, 64 * 1024 * 1024);
+    data.resize(readLimit);
+    qsizetype total = 0;
+    const int fd = file.handle();
+    if (fd < 0) {
+        qCWarning(qt_lcDebugPlugins, "%ls: failed to acquire file descriptor: %ls",
+                  qUtf16Printable(library), qUtf16Printable(file.errorString()));
+        return {};
+    }
+    while (total < readLimit) {
+        const qint64 chunk = ::pread(fd, data.data() + total, size_t(readLimit - total), off_t(total));
+        if (chunk < 0) {
+            qCWarning(qt_lcDebugPlugins, "%ls: failed to pread for metadata scan: %ls",
+                      qUtf16Printable(library), qUtf16Printable(qt_error_string(errno)));
+            return {};
+        }
+        if (chunk == 0)
+            break;
+        total += chunk;
+    }
+    data.truncate(total);
+    filedata = data.constData();
+    fdlen = data.size();
+    if (filedata == nullptr || fdlen == 0) {
+        qCWarning(qt_lcDebugPlugins, "%ls: failed to read for metadata scan: %ls",
+                  qUtf16Printable(library), qUtf16Printable(file.errorString()));
+        return {};
+    }
+#else
+    filedata = reinterpret_cast<char *>(file.map(0, fdlen));
+#endif
 
 #ifdef Q_OS_UNIX
     if (filedata == nullptr) {
@@ -241,7 +279,6 @@
         return {};
     }
 #else
-    QByteArray data;
     if (filedata == nullptr) {
         // It's unknown at this point whether Windows supports LoadLibrary() on
         // files that fail to CreateFileMapping / MapViewOfFile, so we err on

diff -ruwN source-old/src/corelib/global/qsimd.cpp source/src/corelib/global/qsimd.cpp
--- source-old/src/corelib/global/qsimd.cpp	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/global/qsimd.cpp	2026-04-16 00:00:00.000000000 +0000
@@ -377,7 +377,11 @@
 static void xgetbv(uint in, uint &eax, uint &edx)
 {
-#if (defined(Q_CC_GNU) && !defined(Q_CC_EMSCRIPTEN)) || defined(Q_CC_GHS)
+#ifdef Q_OS_REDOX
+    Q_UNUSED(in);
+    eax = 0;
+    edx = 0;
+#elif (defined(Q_CC_GNU) && !defined(Q_CC_EMSCRIPTEN)) || defined(Q_CC_GHS)
     asm (".byte 0x0F, 0x01, 0xD0" // xgetbv instruction
         : "=a" (eax), "=d" (edx)
         : "c" (in));

diff -ruwN source-old/src/corelib/io/qfilesystemengine_unix.cpp source/src/corelib/io/qfilesystemengine_unix.cpp
--- source-old/src/corelib/io/qfilesystemengine_unix.cpp	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/io/qfilesystemengine_unix.cpp	2026-04-13 00:00:00.000000000 +0000
@@ -28,4 +28,21 @@
 #include <errno.h>
 
+#ifdef Q_OS_REDOX
+// relibc does not provide unlinkat/linkat yet (POSIX.1-2008 *at functions).
+// Provide inline stubs that work for AT_FDCWD only - sufficient for
+// FreeDesktop trash operations in this file.
+#include <fcntl.h>
+static inline int unlinkat(int dirfd, const char *pathname, int flags)
+{
+    if (dirfd != AT_FDCWD || flags != 0) { errno = ENOTSUP; return -1; }
+    return unlink(pathname);
+}
+static inline int linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags)
+{
+    if (olddirfd != AT_FDCWD || newdirfd != AT_FDCWD || flags != 0) { errno = ENOTSUP; return -1; }
+    return link(oldpath, newpath);
+}
+#endif
+
 #include <chrono>
 #include <memory> // for std::unique_ptr
diff -ruwN /dev/null source/src/corelib/global/qt_float16_shims.c
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ source/src/corelib/global/qt_float16_shims.c	2026-04-13 00:00:00.000000000 +0000
@@ -0,0 +1,167 @@
+/*
+ * IEEE 754 half-precision soft-float conversion shims for Redox OS
+ *
+ * These compiler runtime functions (__truncsfhf2, __extendhfsf2, etc.) are
+ * normally provided by libgcc or compiler-rt. The Redox cross-toolchain
+ * (x86_64-unknown-redox-gcc, GCC 13.2.0) does not include them because
+ * x86_64 has no native half-precision support (no AVX512FP16).
+ *
+ * Qt6's qfloat16.cpp triggers the compiler to emit calls to these functions.
+ * We provide them here so QtCore links successfully.
+ *
+ * Format: IEEE 754 binary16 (half): 1 sign + 5 exp (bias 15) + 10 mantissa
+ *         IEEE 754 binary32 (float): 1 sign + 8 exp (bias 127) + 23 mantissa
+ *
+ * SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+ */
+
+typedef unsigned short uint16_t;
+typedef unsigned int   uint32_t;
+
+/* --- float16 -> float32 --- */
+float __extendhfsf2(uint16_t h)
+{
+    uint32_t sign = (h >> 15) & 1;
+    uint32_t exp  = (h >> 10) & 0x1f;
+    uint32_t frac = h & 0x3ff;
+    uint32_t bits;
+
+    if (exp == 0) {
+        if (frac == 0) {
+            /* +/- zero */
+            bits = sign << 31;
+        } else {
+            /* Denormalized half: normalize it */
+            exp = 1;
+            while (!(frac & 0x400)) {
+                frac <<= 1;
+                exp--;
+            }
+            frac &= 0x3ff;
+            bits = (sign << 31) | ((exp + 127 - 15) << 23) | (frac << 13);
+        }
+    } else if (exp == 0x1f) {
+        /* Inf or NaN */
+        bits = (sign << 31) | (0xffu << 23) | (frac << 13);
+    } else {
+        /* Normalized */
+        bits = (sign << 31) | ((exp + 127 - 15) << 23) | (frac << 13);
+    }
+
+    union { uint32_t i; float f; } u;
+    u.i = bits;
+    return u.f;
+}
+
+/* --- float32 -> float16 --- */
+uint16_t __truncsfhf2(float f)
+{
+    union { uint32_t i; float f; } u;
+    u.f = f;
+    uint32_t bits = u.i;
+
+    uint32_t sign = (bits >> 31) & 1;
+    int exp  = ((bits >> 23) & 0xff) - 127;
+    uint32_t frac = bits & 0x7fffff;
+
+    /* Handle zero / denormal float input */
+    if (((bits >> 23) & 0xff) == 0) {
+        if (frac == 0) return (uint16_t)(sign << 15);
+        /* Normalize denormal float */
+        while (!(frac & 0x400000)) {
+            frac <<= 1;
+            exp--;
+        }
+        frac &= 0x3fffff;
+    }
+
+    exp += 15;  /* rebias to half-precision */
+
+    if (exp <= 0) {
+        /* Underflow: return +/- zero */
+        return (uint16_t)(sign << 15);
+    }
+    if (exp >= 0x1f) {
+        /* Overflow: return +/- inf */
+        return (uint16_t)((sign << 15) | 0x7c00);
+    }
+
+    /* Round to nearest even: add 0x1000 (half of the gap between half-prec
+       representable values at the LSB position in the 23-bit mantissa). */
+    frac = (frac + 0x1000) >> 13;
+
+    /* Mantissa overflow from rounding */
+    if (frac & 0x400) {
+        frac = 0;
+        exp++;
+        if (exp >= 0x1f)
+            return (uint16_t)((sign << 15) | 0x7c00);
+    }
+
+    return (uint16_t)((sign << 15) | (exp << 10) | frac);
+}
+
+/* --- float16 -> float64 --- */
+double __extendhfdf2(uint16_t h)
+{
+    /* Go through float32 — float has more than enough precision for half */
+    float f = __extendhfsf2(h);
+    return (double)f;
+}
+
+/* --- float64 -> float16 --- */
+uint16_t __truncdfhf2(double d)
+{
+    /* Double -> float -> half: no meaningful precision loss for half output */
+    return __truncsfhf2((float)d);
+}
+
+/* --- long double -> float16 --- */
+uint16_t __truncxfhf2(long double ld)
+{
+    return __truncsfhf2((float)ld);
+}
+
+/* --- half-precision comparisons --- */
+int __eqhf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa == fb;
+}
+int __nehf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa != fb;
+}
+int __lthf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa < fb ? -1 : (fa == fb ? 0 : 1);
+}
+int __lehf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa <= fb ? 0 : 1;
+}
+int __gthf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa > fb ? 1 : (fa == fb ? 0 : -1);
+}
+int __gehf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa >= fb ? 0 : -1;
+}
+int __unordhf2(uint16_t a, uint16_t b)
+{
+    float fa = __extendhfsf2(a);
+    float fb = __extendhfsf2(b);
+    return fa != fa || fb != fb;
+}
diff -ruwN source-old/src/corelib/CMakeLists.txt source/src/corelib/CMakeLists.txt
--- source-old/src/corelib/CMakeLists.txt	2024-12-02 05:39:06.000000000 +0000
+++ source/src/corelib/CMakeLists.txt	2026-04-13 00:00:00.000000000 +0000
@@ -61,6 +61,7 @@
         global/qfloat16.cpp global/qfloat16.h
+        global/qt_float16_shims.c
         global/qforeach.h
         global/qfunctionpointer.h
         global/qgettid_p.h
         global/qglobal.cpp global/qglobal.h global/qglobal_p.h