desktop/source/app/sofficemain.cxx | 15 +++++++++++++--
static/README.wasm.md | 7 +++++++
2 files changed, 20 insertions(+), 2 deletions(-)
New commits:
commit 146fafa691e63de00d6030d88626833ab43d7a65
Author: Stephan Bergmann <stephan.bergm...@allotropia.de>
AuthorDate: Wed Aug 7 15:01:25 2024 +0200
Commit: Stephan Bergmann <stephan.bergm...@allotropia.de>
CommitDate: Wed Aug 7 17:18:34 2024 +0200
I finally understand why we need that hack
...that 77129fbb74bcefde4551d494f029169e7c6026e3 "Emscripten: Add hack to
prepare for --enable-wasm-exceptions" was puzzled about
Change-Id: Iba54a77e3c2a71fe45b97795ca2da0606c3adf41
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/171594
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergm...@allotropia.de>
diff --git a/desktop/source/app/sofficemain.cxx
b/desktop/source/app/sofficemain.cxx
index 9470add3b488..bfa1a66d886a 100644
--- a/desktop/source/app/sofficemain.cxx
+++ b/desktop/source/app/sofficemain.cxx
@@ -75,8 +75,19 @@ extern "C" int DESKTOP_DLLPUBLIC soffice_main()
tools::extendApplicationEnvironment();
#if defined EMSCRIPTEN
- //TODO, see "Experimental (AKA currently broken) WASM exception + SjLj
build" in
- // static/README.wasm.md:
+ //HACK: Qt5 QWasmEventDispatcher::processEvents
+ // (qtbase/src/plugins/platforms/wasm/qwasmeventdispatcher.cpp) calls
+ // emscripten_set_main_loop_arg with simulateInfiniteLoop == true, and as
we use
+ // -fwasm-exceptions (cf. solenv/gbuild/platform/EMSCRIPTEN_INTEL_GCC.mk),
aDesktop allocated on
+ // the stack would run into the issue warned about at
+ //
<https://emscripten.org/docs/api_reference/emscripten.h.html#c.emscripten_set_main_loop>
+ // "Note: Currently, using the new Wasm exception handling and
simulate_infinite_loop == true at
+ // the same time does not work yet in C++ projects that have objects with
destructors on the
+ // stack at the time of the call." (Also see the mailing list thread at
+ // <https://groups.google.com/g/emscripten-discuss/c/xpWDVwyJu-M>
"Implementation of
+ // -fexceptions and -fwasm-exceptions" for why such automatic variables
are destroyed with
+ // -fwasm-exceptions but not with -fexceptions.) So deliberately leak the
Desktop instance
+ // here:
new desktop::Desktop();
#else
desktop::Desktop aDesktop;
diff --git a/static/README.wasm.md b/static/README.wasm.md
index cb5d0aa7fc3e..de595b19b459 100644
--- a/static/README.wasm.md
+++ b/static/README.wasm.md
@@ -69,6 +69,13 @@ With "-opensource -confirm-license" you agree to the open
source license.
./configure -opensource -confirm-license -xplatform wasm-emscripten
-feature-thread -prefix <whatever> QMAKE_CFLAGS+=-sSUPPORT_LONGJMP=wasm
QMAKE_CXXFLAGS+=-sSUPPORT_LONGJMP=wasm
make -j<CORES> module-qtbase
+Do not include `-fwasm-exceptions` in the above `QMAKE_CXXFLAGS`, see
+<https://emscripten.org/docs/api_reference/emscripten.h.html#c.emscripten_set_main_loop>
"Note:
+Currently, using the new Wasm exception handling and simulate_infinite_loop ==
true at the same time
+does not work yet in C++ projects that have objects with destructors on the
stack at the time of the
+call." (Also see the EMSCRIPTEN-specific HACK in soffice_main,
desktop/source/app/sofficemain.cxx,
+for what we need to do to work around that.)
+
Optionally you can add the configure flag "-compile-examples". But then you
also have to
patch at least mkspecs/wasm-emscripten/qmake.conf with EXIT_RUNTIME=0,
otherwise they will
fail to run. In addition, building with examples will break with some of them,
but at that
