QT-Webassembly - Compile Examples

David_001

Hi everybody,

i would like to compile some of the qt examples with emcc compiler, but i have some trouble with it.
I already searched for this error some hours but didn't get a good solution.

So here is what i have done:

1. Downloaded qt web installer (linux) from qt.io
2. Installed qt 5.13 (complete) => with sources and Webassembly
3. => Since 5.13 i think there is no need to compile Webassembly on his own like on 5.12 anymore.
4. Than i installed emcc like the instruction on emscription.org said.

git clone https://github.com/emscripten-core/emsdk.git
cd emsdk
git pull
./emsdk install latest
./emsdk activate latest
source ./emsdk_env.sh
sudo apt-get install python2.7
sudo apt-get install cmake
sudo apt-get install default-jre

After i have done that i verified the emcc installation. Everything is fine.

5. Started QtCreator => There is already an QtWebassembly Kit but without an Compiler
6. Added emcc and em++ compiler to QtCreator (custom-compiler)

Name: emcc
Compiler-Path:  ~/work/privat/project/emc/emsdk/fastcomp/emscripten/emcc
Path to Make: /usr/bin/make
ABI: x86,linux,generic, elf,64bit
QT-mkspecs: empty

Name: em++
Compiler-Path:  ~/work/privat/project/emc/emsdk/fastcomp/emscripten/em++
Path to Make: /usr/bin/make
ABI: x86,linux,generic, elf,64bit
QT-mkspecs: empty

Everything else on Default.

7. Added Compiler to QtWebassembly-Kit
8. Opened any example from Qt and also made a simple Window with an anchors.fill red Rectangle
9. Compiling staring like always BUTTTTT than there where some issues.

warning: unexpected return type i32 in call to 'lseek', should be i64
warning: unexpected argument type i32 at index 5 in call to '__mmap', should be i64
warning: unexpected argument type i32 at index 5 in call to '__mmap', should be i64
warning: unexpected argument type i32 at index 5 in call to '__mmap', should be i64
warning: unexpected argument type i32 at index 5 in call to '__mmap', should be i64
warning: unexpected argument type i32 at index 5 in call to '__mmap', should be i64
warning: unexpected argument type i32 at index 1 in call to 'lseek', should be i64
warning: unexpected return type i32 in call to 'lseek', should be i64
warning: unexpected argument type i32 at index 5 in call to '__mmap', should be i64
emcc: warning: cannot represent a NaN literal '0x1b1af280' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
  in   ret double 0x7FF4000000000000 in _ZL7qt_snanv() 
emcc: warning: cannot represent a NaN literal '0x1b1af280' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
  in   ret double 0x7FF4000000000000 in _ZL7qt_snanv.24722() 
warning: unexpected return type i32 in call to '__ftello', should be i64
warning: unexpected argument type i32 at index 1 in call to 'lseek', should be i64
warning: unexpected return type i32 in call to 'lseek', should be i64

After a while QtCreator starts printing a lot lot lot lot output in assmbly (takes lot of time)

alt text

Ending up with this error:

fatal: error in validating output shared:error:
--total-memory=16777216 --trap-mode=clamp -Os --mem-init=./untitled.js.mem --mem-base=1024 --wasm-only -g -o ./untitled.wast -S --mvp-features' failed (1)

As i said i already searched for it at google and tried some option i found:

QMAKE_CXXFLAGS += -s WASM=0
QMAKE_CXXFLAGS += -s TOTAL_MEMORY=52428800

Still the same :( Does anyone knows where i made a mistake ? What am i doing wrong?

lorn.potter

@david_001 What version of emscripten do you have?
Qt 5.13 webassembly requires 1.38.27
https://wiki.qt.io/Qt_for_WebAssembly

David_001

Lastest => 1.38.39 shouldn't it work with a newer version as well?

lorn.potter

@david_001
emscripten can and do make radical and non compatible changes. So we decided that we would tie a certain Qt version to a certain emscripten version.
We have not made any changes to enforce this, or at least to point out to the developer that a certain version is required.

David_001

I used the Version you recommended, with the Version 1.38.27 the compilation will successfully.

Here a Tutorial to setup:

1. Downloaded qt web installer (linux) from qt.io
2. Installed qt 5.13 (complete) => with sources and Webassembly
3. => Since 5.13 i think there is no need to compile Webassembly on his own like on 5.12 anymore.
4. Than i installed emcc like the instruction on emscription.org said.

git clone https://github.com/emscripten-core/emsdk.git
cd emsdk
git pull
./emsdk install sdk-1.38.27-64bit
./emsdk activate sdk-1.38.27-64bit
source ./emsdk_env.sh
sudo apt-get install python2.7
sudo apt-get install cmake
sudo apt-get install default-jre

After i have done that i verified the emcc installation. Everything is fine.

5. Started QtCreator => There is already an QtWebassembly Kit but without an Compiler
6. Added emcc and em++ compiler to QtCreator (custom-compiler)

Name: emcc
Compiler-Path:  ~/work/privat/project/emsdk/emscripten/1.38.27/emcc
Path to Make: /usr/bin/make
ABI: x86,linux,generic, elf,64bit
QT-mkspecs: empty

Name: em++
Compiler-Path:  ~/work/privat/project/emsdk/emscripten/1.38.27/em++
Path to Make: /usr/bin/make
ABI: x86,linux,generic, elf,64bit
QT-mkspecs: empty

Everything else on Default.

7. Added Compiler to QtWebassembly-Kit
8. DONE

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