wasm: allow apps to override EXPORT_RUNTIME_METHODS

Developers can add to Emscripten's EXPORT_RUNTIME_METHODS
by defining their own using:
QT_WASM_EXTRA_EXPORTED_METHODS

Which will add on to Qt's default exported runtime methods
of UTF16ToString,stringToUTF16

for cmake:
set_target_properties(<target> PROPERTIES QT_WASM_EXTRA_EXPORTED_METHODS "ccall,cwrap")
or
set(QT_WASM_EXTRA_EXPORTED_METHODS "ccall,cwrap")

for qmake:
QT_WASM_EXTRA_EXPORTED_METHODS = ccall,cwrap

Done-with: Mikolaj Boc
Fixes: QTBUG-104882
Pick-to: 6.4
Change-Id: I9678bdb7b077aaa8527057212ea4e161c0be0b60
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtExecutableHelpers.cmake

@@ -40,8 +40,10 @@ function(qt_internal_add_executable name)
     endif()
 
     if(WASM)
+        qt_internal_wasm_add_finalizers("${name}")
         _qt_internal_wasm_add_target_helpers("${name}")
     endif()
+
     if (arg_VERSION)
         if(arg_VERSION MATCHES "[0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+")
             # nothing to do

cmake/QtWasmHelpers.cmake

@@ -7,7 +7,6 @@ function (qt_internal_setup_wasm_target_properties wasmTarget)
 
     target_link_options("${wasmTarget}" INTERFACE
     "SHELL:-s ERROR_ON_UNDEFINED_SYMBOLS=1"
-    "SHELL:-s EXPORTED_RUNTIME_METHODS=UTF16ToString,stringToUTF16"
     "SHELL:-s MAX_WEBGL_VERSION=2"
     "SHELL:-s FETCH=1"
     "SHELL:-s WASM_BIGINT=1")
@@ -80,3 +79,9 @@ function (qt_internal_setup_wasm_target_properties wasmTarget)
         target_compile_definitions("${wasmTarget}" INTERFACE QT_HAVE_EMSCRIPTEN_ASYNCIFY)
     endif()
 endfunction()
+
+function(qt_internal_wasm_add_finalizers target)
+    qt_add_list_file_finalizer(_qt_internal_add_wasm_extra_exported_methods ${target})
+endfunction()
+
+

mkspecs/features/wasm/wasm.prf

@@ -7,6 +7,14 @@ isEmpty(DESTDIR): DESTDIR = $$OUT_PWD
 exists($$QMAKE_QT_CONFIG) {
 ## this may be subject to change
 
+    ## qmake puts a space if done otherwise
+    !isEmpty(QT_WASM_EXTRA_EXPORTED_METHODS): {
+        EXPORTED_METHODS = UTF16ToString,stringToUTF16,$$QT_WASM_EXTRA_EXPORTED_METHODS
+    } else {
+         EXPORTED_METHODS = UTF16ToString,stringToUTF16
+    }
+    EMCC_LFLAGS += -s EXPORTED_RUNTIME_METHODS=$$EXPORTED_METHODS
+
     qtConfig(thread) {
 
         EMCC_LFLAGS += -pthread

mkspecs/wasm-emscripten/qmake.conf

@@ -32,7 +32,6 @@ EMCC_COMMON_LFLAGS += \
     -s WASM=1 \
     -s MAX_WEBGL_VERSION=2 \
     -s ERROR_ON_UNDEFINED_SYMBOLS=1 \
-    -s EXPORTED_RUNTIME_METHODS=UTF16ToString,stringToUTF16 \
     --bind \
     -s FETCH=1 \
     -s MODULARIZE=1 \

src/corelib/Qt6CoreMacros.cmake

@@ -650,6 +650,7 @@ function(_qt_internal_finalize_executable target)
 
     if(EMSCRIPTEN)
         _qt_internal_wasm_add_target_helpers("${target}")
+        _qt_internal_add_wasm_extra_exported_methods("${target}")
     endif()
     if(IOS)
         _qt_internal_finalize_ios_app("${target}")

src/corelib/Qt6WasmMacros.cmake

@@ -60,3 +60,21 @@ function(_qt_internal_wasm_add_target_helpers target)
     endif()
 endfunction()
 
+function(_qt_internal_add_wasm_extra_exported_methods target)
+    get_target_property(wasm_extra_exported_methods "${target}" QT_WASM_EXTRA_EXPORTED_METHODS)
+
+    if(NOT wasm_extra_exported_methods)
+        set(wasm_extra_exported_methods ${QT_WASM_EXTRA_EXPORTED_METHODS})
+    endif()
+
+    if(wasm_extra_exported_methods)
+        target_link_options("${target}" PRIVATE
+        "SHELL:-s EXPORTED_RUNTIME_METHODS=UTF16ToString,stringToUTF16,${wasm_extra_exported_methods}"
+        )
+    else()
+        # an errant dangling comma will break this
+        target_link_options("${target}" PRIVATE
+            "SHELL:-s EXPORTED_RUNTIME_METHODS=UTF16ToString,stringToUTF16"
+        )
+    endif()
+endfunction()