9498ec7239
Most of the folders now have README.md in Markdown format and it is
possible to create html docs out of them which is available at:
https://docs.libreoffice.org/
The content of README file was previously converted to Markdown
format in commit d19299f579
, so only
the rename of the README file was needed.
Change-Id: Ib030676a70194fdb24aea066ec985c2f95ee4b3e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/123449
Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>
Tested-by: Jenkins
302 lines
11 KiB
Markdown
302 lines
11 KiB
Markdown
# Support for Emscripten Cross Build
|
|
|
|
This module provides support for emscripten cross build
|
|
|
|
## Status
|
|
|
|
$ make
|
|
$ emrun --serve_after_close instdir/program/ui-previewer.html
|
|
|
|
The `ui-previewer` "binary" will "crash" with memory alignment problems.
|
|
|
|
You can run the WASM mandelbrot Qt example, if you copy its HTML
|
|
and the qtloader.js from the Qt's example folder after build with:
|
|
|
|
$ emrun --serve_after_close workdir/LinkTarget/Executable/mandelbrot.html
|
|
|
|
REMINDER: Always start new tabs in the browser, reload might fail / cache!
|
|
|
|
|
|
## Setup for the LO WASM build (with Qt)
|
|
|
|
We're using Qt 5.15 with the officially supported emscripten v1.39.8.
|
|
But there are several potential problems with threads and exceptions, so this will likely
|
|
change later to a newer emscripten.
|
|
|
|
Qt WASM is not yet used with LO, just if you're wondering!
|
|
|
|
- See below under Docker build for another build option
|
|
|
|
### Setup emscripten
|
|
|
|
<https://emscripten.org/docs/getting_started/index.html>
|
|
|
|
git clone https://github.com/emscripten-core/emsdk.git
|
|
./emsdk install 1.39.8
|
|
./emsdk activate --embedded 1.39.8
|
|
|
|
Example `bashrc` scriptlet:
|
|
|
|
EMSDK_ENV=$HOME/Development/libreoffice/git_emsdk/emsdk_env.sh
|
|
[ -f "$EMSDK_ENV" ] && \. "$EMSDK_ENV" 1>/dev/null 2>&1
|
|
|
|
### Setup Qt
|
|
|
|
<https://doc.qt.io/qt-5/wasm.html>
|
|
|
|
I originally build the Qt 5.15 branch, but probably better to build a tag like v5.15.2.
|
|
|
|
So:
|
|
|
|
git clone https://github.com/qt/qt5.git
|
|
cd qt5
|
|
git checkout v5.15.2
|
|
./init-repository
|
|
./configure -xplatform wasm-emscripten -feature-thread -compile-examples -prefix $PWD/qtbase
|
|
make -j<CORES> module-qtbase module-qtdeclarative
|
|
|
|
Building with examples will break with some of them, but at that point Qt already works.
|
|
|
|
At some point Qt configure failed for me with:
|
|
|
|
"Checking for target architecture... Project ERROR: target architecture detection binary not found."
|
|
|
|
What seems to have fixed this was to run "emsdk activate 1.39.8" again.
|
|
|
|
Current Qt fails to start the demo webserver: <https://bugreports.qt.io/browse/QTCREATORBUG-24072>
|
|
|
|
Use `emrun --serve_after_close` to run Qt WASM demos
|
|
|
|
Enabling multi-thread support in Firefox is a bit of work with older versions:
|
|
|
|
- <https://bugzilla.mozilla.org/show_bug.cgi?id=1477743#c7>
|
|
- <https://wiki.qt.io/Qt_for_WebAssembly#Multithreading_Support>
|
|
- <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer>
|
|
|
|
|
|
### Setup LO
|
|
|
|
`autogen.sh` is patched to use emconfigure. That basically sets various environment vars,
|
|
especially `EMMAKEN_JUST_CONFIGURE`, which will create the correct output file names, checked by
|
|
`configure` (`a.out`).
|
|
|
|
There's a distro config for WASM (work in progress), that gets your
|
|
defaults right (and currently disables a ton of 3rd party stuff which
|
|
is not essential).
|
|
|
|
Recommended configure setup is thusly:
|
|
|
|
* grab defaults
|
|
`--with-distro=LibreOfficeWASM32`
|
|
|
|
* local config
|
|
`QT5DIR=/dir/of/git_qt5/qtbase`
|
|
|
|
* if you want to use ccache on both sides of the build
|
|
`--with-build-platform-configure-options=--enable-ccache`
|
|
`--enable-ccache`
|
|
|
|
### Using Docker to cross-build with emscripten
|
|
|
|
If you prefer a controlled environment (sadly emsdk install/activate
|
|
is _not_ stable over time, as e.g. nodejs versions evolve), that is
|
|
easy to replicate across different machines - consider the docker
|
|
images we're providing.
|
|
|
|
Config/setup file see
|
|
<https://git.libreoffice.org/lode/+/ccb36979563635b51215477455953252c99ec013>
|
|
|
|
Run
|
|
|
|
docker-compose build
|
|
|
|
in the lode/docker dir to get the container prepared. Run
|
|
|
|
PARALLELISM=4 BUILD_OPTIONS= BUILD_TARGET=build docker-compose run --rm -e PARALLELISM -e BUILD_TARGET -e BUILD_OPTIONS builder
|
|
|
|
to perform an actual `srcdir != builddir` build; the container mounts
|
|
checked-out git repo and output dir via `docker-compose.yml` (so make
|
|
sure the path names there match your setup):
|
|
|
|
The lode setup expects, inside the lode/docker subdir, the following directories:
|
|
|
|
- core (`git checkout`)
|
|
- workdir (the output dir - gets written into)
|
|
- cache (`ccache tree`)
|
|
- tarballs (external project tarballs gets written and cached there)
|
|
|
|
|
|
## Ideas for an UNO bridge implementation
|
|
|
|
My post to Discord #emscripten:
|
|
|
|
"I'm looking for a way to do an abstract call
|
|
from one WASM C++ object to another WASM C++ object, so like FFI / WebIDL,
|
|
just within WASM. All my code is C++ and normally I have bridge code, with
|
|
assembler to implement the function call /RTTI and exception semantics of the
|
|
specified platform. Code is at
|
|
<https://cgit.freedesktop.org/libreoffice/core/tree/bridges/source/cpp_uno>.
|
|
I've read a bit about `call_indirect` and stuff, but I don't have yet a good
|
|
idea, how I could implement this (and there is an initial feature/wasm branch
|
|
for the interested). I probably need some fixed lookup table, like on iOS,
|
|
because AFAIK you can't dynamically generate code in WASM. So any pointers or
|
|
ideas for an implementation? I can disassemble some minimalistic WASM example
|
|
and read clang code for `WASM_EmscriptenInvoke`, but if there were some
|
|
standalone code or documentation I'm missing, that would be nice to know."
|
|
|
|
We basically would go the same way then the other backends. Write the bridge in
|
|
C++, which is probably largely boilerplate code, but the function call in WAT
|
|
(<https://github.com/WebAssembly/wabt>) based on the LLVM WASM calling
|
|
conventions in `WASM_EmscriptenInvoke`. I didn't get a reply to that question for
|
|
hours. Maybe I'll open an Emscripten issue, if we really have to implement
|
|
this.
|
|
|
|
WASM dynamic dispatch:
|
|
|
|
- <https://fitzgeraldnick.com/2018/04/26/how-does-dynamic-dispatch-work-in-wasm.html>
|
|
|
|
|
|
## Workaround for eventual clang WASM compiler bug
|
|
|
|
````
|
|
sc/source/core/data/attarray.cxx:378:44: error: call to member function 'erase' is ambiguous
|
|
aNewCondFormatData.erase(nIndex);
|
|
~~~~~~~~~~~~~~~~~~~^~~~~
|
|
include/o3tl/sorted_vector.hxx:86:15: note: candidate function
|
|
size_type erase( const Value& x )
|
|
^
|
|
include/o3tl/sorted_vector.hxx:97:10: note: candidate function
|
|
void erase( size_t index )
|
|
````
|
|
|
|
This is currently patched by using `x.erase` (`x.begin() + nIndex`).
|
|
|
|
There shouldn't be an ambiguity, because of "[WebAssembly] Change size_t to `unsigned long`."
|
|
<https://reviews.llvm.org/rGdf07a35912d78781ed6a62a7c032bfef5085a4f5#change-IrS9f6jH6PFq>,
|
|
from "Jul 23 2018" which pre-dates the emscripten tag 1.39.8 from 02/14/2020 by ~1.5y.
|
|
|
|
|
|
## Tools for problem diagnosis
|
|
|
|
* `nm -s` should list the symbols in the archive, based on the index generated by ranlib.
|
|
If you get linking errors that archive has no index.
|
|
|
|
|
|
## Emscripten filesystem access with threads
|
|
|
|
This is closed, but not really fixed IMHO:
|
|
|
|
- <https://github.com/emscripten-core/emscripten/issues/3922>
|
|
|
|
|
|
## Dynamic libraries `/` modules in emscripten
|
|
|
|
There is a good summary in:
|
|
|
|
- <https://bugreports.qt.io/browse/QTBUG-63925>
|
|
|
|
Summary: you can't use modules and threads.
|
|
|
|
This is mentioned at the end of:
|
|
|
|
- <https://github.com/emscripten-core/emscripten/wiki/Linking>
|
|
|
|
The usage of `MAIN_MODULE` and `SIDE_MODULE` has other problems, a major one IMHO is symbol resolution at runtime only.
|
|
So this works really more like plugins in the sense of symbol resolution without dependencies `/` rpath.
|
|
|
|
There is some clang-level dynamic-linking in progress (WASM dlload). The following link is already a bit old,
|
|
but I found it a god summary of problems to expect:
|
|
|
|
- <https://iandouglasscott.com/2019/07/18/experimenting-with-webassembly-dynamic-linking-with-clang/>
|
|
|
|
|
|
## Mixed information, links, problems, TODO
|
|
|
|
More info on Qt WASM emscripten pthreads:
|
|
|
|
- <https://wiki.qt.io/Qt_for_WebAssembly#Multithreading_Support>
|
|
|
|
WASM needs `-pthread` at compile, not just link time for atomics support. Alternatively you can provide
|
|
`-s USE_PTHREADS=1`, but both don't seem to work reliable, so best provide both.
|
|
<https://github.com/emscripten-core/emscripten/issues/10370>
|
|
|
|
The output file must have the prefix .o, otherwise the WASM files will get a
|
|
`node.js` shebang (!) and ranlib won't be able to index the library (link errors).
|
|
|
|
Qt with threads has further memory limit. From Qt configure:
|
|
````
|
|
Project MESSAGE: Setting PTHREAD_POOL_SIZE to 4
|
|
Project MESSAGE: Setting TOTAL_MEMORY to 1GB
|
|
````
|
|
|
|
You can actually allocate 4GB:
|
|
|
|
- <https://bugzilla.mozilla.org/show_bug.cgi?id=1392234>
|
|
|
|
LO uses a nested event loop to run dialogs in general, but that won't work, because you can't drive
|
|
the browser event loop. like VCL does with the system event loop in the various VCL backends.
|
|
Changing this will need some major work (basically dropping Application::Execute).
|
|
|
|
But with the know problems with exceptions and threads, this might change:
|
|
|
|
- <https://github.com/emscripten-core/emscripten/pull/11518>
|
|
- <https://github.com/emscripten-core/emscripten/issues/11503>
|
|
- <https://github.com/emscripten-core/emscripten/issues/11233>
|
|
- <https://github.com/emscripten-core/emscripten/issues/12035>
|
|
|
|
We're also using emconfigure at the moment. Originally I patched emscripten, because it
|
|
wouldn't create the correct a.out file for C++ configure tests. Later I found that
|
|
the `emconfigure` sets `EMMAKEN_JUST_CONFIGURE` to work around the problem.
|
|
|
|
ICU bug:
|
|
|
|
- <https://github.com/emscripten-core/emscripten/issues/10129>
|
|
|
|
Alternative, probably:
|
|
|
|
- <https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Intl>
|
|
|
|
There is a wasm64, but that still uses 32bit pointers!
|
|
|
|
Old outdated docs:
|
|
|
|
- <https://wiki.documentfoundation.org/Development/Emscripten>
|
|
|
|
Reverted patch:
|
|
|
|
- <https://cgit.freedesktop.org/libreoffice/core/commit/?id=0e21f6619c72f1e17a7b0a52b6317810973d8a3e>
|
|
|
|
Generally <https://emscripten.org/docs/porting>:
|
|
|
|
- <https://emscripten.org/docs/porting/guidelines/api_limitations.html#api-limitations>
|
|
- <https://emscripten.org/docs/porting/files/file_systems_overview.html#file-system-overview>
|
|
- <https://emscripten.org/docs/porting/pthreads.html>
|
|
- <https://emscripten.org/docs/porting/emscripten-runtime-environment.html>
|
|
|
|
This will be interesting:
|
|
|
|
- <https://emscripten.org/docs/getting_started/FAQ.html#how-do-i-run-an-event-loop>
|
|
|
|
This didn't help much yet:
|
|
|
|
- <https://github.com/emscripten-ports>
|
|
|
|
Emscripten supports standalone WASI binaries:
|
|
|
|
- <https://github.com/emscripten-core/emscripten/wiki/WebAssembly-Standalone>
|
|
- <https://www.qt.io/qt-examples-for-webassembly>
|
|
- <http://qtandeverything.blogspot.com/2017/06/qt-for-web-assembly.html>
|
|
- <http://qtandeverything.blogspot.com/2020/>
|
|
- <https://emscripten.org/docs/api_reference/Filesystem-API.html>
|
|
- <https://discuss.python.org/t/add-a-webassembly-wasm-runtime/3957/12>
|
|
- <http://git.savannah.gnu.org/cgit/config.git>
|
|
- <https://webassembly.org/specs/>
|
|
- <https://developer.chrome.com/docs/native-client/>
|
|
- <https://emscripten.org/docs/getting_started/downloads.html>
|
|
- <https://github.com/openpgpjs/openpgpjs/blob/master/README.md#getting-started>
|
|
- <https://developer.mozilla.org/en-US/docs/WebAssembly/Using_the_JavaScript_API>
|
|
- <https://github.com/bytecodealliance/wasmtime/blob/main/docs/WASI-intro.md>
|
|
- <https://www.ip6.li/de/security/x.509_kochbuch/openssl-fuer-webassembly-compilieren>
|
|
- <https://emscripten.org/docs/introducing_emscripten/about_emscripten.html#about-emscripten-porting-code>
|
|
- <https://emscripten.org/docs/compiling/Building-Projects.html>
|
|
|