chore: wasi support

This PR adds rudimentary WebAssembly/WASI support
by excluding unsupported calls to non-implemented
WASI/posix syscalls.

This also adds an OS definition for WASI in Qt.

Author: Rio Martinez

src/corelib/global/qsystemdetection.h

@@ -130,6 +130,8 @@
 #elif defined(__HAIKU__)
 #  define Q_OS_HAIKU
 #elif defined(__MAKEDEPEND__)
+#elif defined(__wasi__)
+#  define Q_OS_WASI
 #else
 #  error "Qt has not been ported to this OS - see http://www.qt-project.org/"
 #endif

src/corelib/kernel/qeventdispatcher_unix.cpp

@@ -196,8 +196,10 @@ int QThreadPipe::check(const pollfd &pfd)
 
 QEventDispatcherUNIXPrivate::QEventDispatcherUNIXPrivate()
 {
+#if !defined(Q_OS_WASI)
     if (Q_UNLIKELY(threadPipe.init() == false))
         qFatal("QEventDispatcherUNIXPrivate(): Cannot continue without a thread pipe");
+#endif
 }
 
 QEventDispatcherUNIXPrivate::~QEventDispatcherUNIXPrivate()

src/gui/painting/qgrayraster_p.h

@@ -55,7 +55,11 @@
 
 /* Minimum buffer size for raster object, that accounts
    for TWorker and TCell sizes.*/
-#define MINIMUM_POOL_SIZE 8192
+#if !defined(Q_OS_WASI)
+#  define MINIMUM_POOL_SIZE 8192
+#else
+#  define MINIMUM_POOL_SIZE 81920
+#endif
 
   QT_FT_EXPORT_VAR( const QT_FT_Raster_Funcs )  QT_MANGLE_NAMESPACE(qt_ft_grays_raster);
 

src/testlib/qtestcrashhandler_p.h

@@ -39,7 +39,7 @@ namespace CrashHandler {
     bool alreadyDebugging();
     void blockUnixSignals();
 
-#if !defined(Q_OS_WASM) || QT_CONFIG(thread)
+#if !(defined(Q_OS_WASM) || defined(Q_OS_WASI)) || QT_CONFIG(thread)
     void printTestRunTime();
     void generateStackTrace(quintptr ip = 0);
 #endif
@@ -54,7 +54,7 @@ namespace CrashHandler {
         WindowsFaultHandler();
     };
     using FatalSignalHandler = WindowsFaultHandler;
-#elif defined(Q_OS_UNIX) && !defined(Q_OS_WASM)
+#elif defined(Q_OS_UNIX) && !defined(Q_OS_WASM) && !defined(Q_OS_WASI)
     class Q_TESTLIB_EXPORT FatalSignalHandler
     {
     public:

src/testlib/qtestcrashhandler_unix.cpp

@@ -414,7 +414,7 @@ void generateStackTrace(quintptr ip)
     (void) prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
 #  endif
 
-#  if !defined(Q_OS_INTEGRITY) && !defined(Q_OS_VXWORKS)
+#  if !defined(Q_OS_INTEGRITY) && !defined(Q_OS_VXWORKS) && !defined(Q_OS_WASI)
     writeToStderr("\n=== Stack trace ===\n");
 
     // execlp() requires null-termination, so call the default constructor
@@ -488,7 +488,7 @@ void generateStackTrace(quintptr ip)
 #  endif // !Q_OS_INTEGRITY && !Q_OS_VXWORKS
 }
 
-#ifndef Q_OS_WASM // no signal handling for WASM
+#if !(defined(Q_OS_WASM) || defined(Q_OS_WASI)) // no signal handling for WASM or WASI
 void blockUnixSignals()
 {
     // Block most Unix signals so the WatchDog thread won't be called when
@@ -827,7 +827,7 @@ void actionHandler(int signum, siginfo_t *info, void *ucontext)
     // we shouldn't reach here!
     std::abort();
 }
-#endif // !defined(Q_OS_WASM)
+#endif // !(defined(Q_OS_WASM) || defined(Q_OS_WASI))
 
 } // namespace CrashHandler
 } // namespace QTest