Using Emscripten in CMake doesn't output html

[techie-guy]

Version of emscripten/emsdk:
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.25 (febd44b)
clang version 16.0.0 (https://github.com/llvm/llvm-project effd75bda4b1a9b26e554c1cda3e3b4c72fa0aa8)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: D:\sdk\emsdk\upstream\bin

I am trying to add emscripten support to my project, but when I specify -o output.html in target_link_options, it doesn't output a html file, but a js and a wasm file

Using set(CMAKE_EXECUTABLE_SUFFIX ".html") also doesn't work

The CMakeLists.txt snippet

set(CMAKE_TOOLCHAIN_FILE $ENV{EMSDK_HOME}/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake)
set(CMAKE_EXECUTABLE_SUFFIX ".html")
set(LINK_OPTIONS ${LINK_OPTIONS} -o output.html -sMIN_WEBGL_VERSION=2 -sMAX_WEBGL_VERSION=2 -sUSE_GLFW=3 -sWASM=1)
set(LINK_LIBRARIES ${LINK_LIBRARIES} -lglfw3 -lGLESv2 -lEGL)

[sbc100]

CMAKE_EXECUTABLE_SUFFIX seems to work for me, and we do have tests for it.

Does the following not work for you:

$ cat CMakeLists.txt 
set(CMAKE_EXECUTABLE_SUFFIX ".html")
add_executable(hello_world "hello.c")
$ emcmake cmake . -G Ninja
$ ninja
$ ninja -v
[1/1] : && /usr/local/google/home/sbc/dev/wasm/emscripten/emcc   CMakeFiles/hello_world.dir/hello.c.o -o hello_world.html  
$ ls hello_world*
hello_world.html  hello_world.js  hello_world.wasm*

[techie-guy]

No, it doesn't work.

But, using ninja -v, I got this:

[10/10] cmd.exe /C "cd . && D:\dev\programs\emsdk\upstream\emscripten\em++.bat  -o listboard.html -sUSE_GLFW=3 -sWASM=1 -sALLOW_MEMORY_GROWTH=1 -sNO_EXIT_RUNTIME=0 -sASSERTIONS=1 CMakeFiles/listboard.dir/src/main.cpp.o CMakeFiles/listboard.dir/src/Application.cpp.o CMakeFiles/listboard.dir/third_party/imgui/imgui.cpp.o CMakeFiles/listboard.dir/third_party/imgui/imgui_demo.cpp.o CMakeFiles/listboard.dir/third_party/imgui/imgui_draw.cpp.o CMakeFiles/listboard.dir/third_party/imgui/imgui_tables.cpp.o CMakeFiles/listboard.dir/third_party/imgui/imgui_widgets.cpp.o CMakeFiles/listboard.dir/third_party/imgui/backends/imgui_impl_glfw.cpp.o CMakeFiles/listboard.dir/third_party/imgui/backends/imgui_impl_opengl3.cpp.o -o listboard.js  -lglfw3  -lGLESv2  -lEGL && cd ."

During the last step i.e linking, something is passing -o listboard.js after -o listboard.html. That's the reason it outputs the js file instead of html.

But, what's passing the -o listboard.js argument?

[sbc100]

I have no idea I'm afraid. BTW the explicit -o should not be need. CMAKE_EXECUTABLE_SUFFIX should be enough. Can you try removing the LINK_OPTIONS that adds the -o?

Are you using emcmake? Can you share the full cmake command and as much as possible of CMakeList.txt.

[techie-guy]

No, I'm not using emcmake

The cmake command: COMPILE_FOR_WASM=1 cmake ..

The CMakeLists.txt

cmake_minimum_required(VERSION 3.2.1)

set(CMAKE_CXX_STANDARD 14)

set(IMGUI_DIR third_party/imgui)
set(GLAD_DIR third_party/glad)

set(IMGUI_SOURCES ${IMGUI_DIR}/imgui.cpp ${IMGUI_DIR}/imgui_demo.cpp ${IMGUI_DIR}/imgui_draw.cpp ${IMGUI_DIR}/imgui_tables.cpp ${IMGUI_DIR}/imgui_widgets.cpp ${IMGUI_DIR}/backends/imgui_impl_glfw.cpp ${IMGUI_DIR}/backends/imgui_impl_opengl3.cpp)
set(SOURCES src/main.cpp src/Application.cpp ${IMGUI_SOURCES})

set(COMPILE_DEFINITIONS)
set(COMPILE_OPTIONS)
set(LINK_OPTIONS)
set(LINK_LIBRARIES)
set(INCLUDE_DIRS include ${IMGUI_DIR} ${IMGUI_DIR}/backends)

if($ENV{COMPILE_FOR_WASM})
	set(COMPILE_DEFINITIONS _PLATFORM_WASM)
	set(CMAKE_TOOLCHAIN_FILE $ENV{EMSDK_HOME}/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake)
	set(CMAKE_EXECUTABLE_SUFFIX ".html")
	set(LINK_OPTIONS ${LINK_OPTIONS} -sUSE_GLFW=3 -sWASM=1 -sALLOW_MEMORY_GROWTH=1 -sNO_EXIT_RUNTIME=0 -sASSERTIONS=1)
	set(LINK_LIBRARIES ${LINK_LIBRARIES} -lglfw3 -lGLESv2 -lEGL)
else()
	set(COMPILE_DEFINITIONS _PLATFORM_NATIVE)
	find_package(PkgConfig REQUIRED)
	pkg_check_modules(GLFW3 REQUIRED glfw3)
	set(INCLUDE_DIRS ${INCLUDE_DIRS} ${GLAD_DIR}/include)
	set(LINK_LIBRARIES ${LINK_LIBRARIES} ${GLFW3_LIBRARIES})
endif()

project(listboard)

add_executable(listboard ${SOURCES})
target_compile_options(listboard PUBLIC ${COMPILE_OPTIONS})
target_compile_definitions(listboard PUBLIC ${COMPILE_DEFINITIONS})
target_include_directories(listboard PUBLIC ${INCLUDE_DIRS})
target_link_options(listboard PUBLIC ${LINK_OPTIONS})
target_link_libraries(listboard PUBLIC ${LINK_LIBRARIES})

The complete project: https://github.com/techie-guy/listboard

[sbc100]

Can you try using emcmake or passing -DCMAKE_TOOLCHAIN_FILE=... on the command line instead of in the CMakeLists.txt?

[techie-guy]

I passed the toolchain file on the command line and used emcmake cmake .. -G Ninja, still the same js output!

[techie-guy]

But I did find one thing.
On modifying the CMAKE_EXECUTABLE_SUFFIX in the toolchain file from .js to .html and using COMPILE_FOR_WASM=1 cmake .. , it does output the html file.

In the toolchain file at path/to/emscripten_sdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake

set(CMAKE_EXECUTABLE_SUFFIX ".html")

[starball5]

Ahaha I found you again (I saw and answered your question on Stack Overflow). You folks can find the solution there.

My suggestion to prevent issues like from happening is for the Emscripten toolchain file to only set a default value for CMAKE_EXECUTABLE_SUFFIX if a value hasn't already been defined by the user. This can be done using if(DEFINED ...). I came to the issues page for this repo to raise this suggestion and found this issue ticket :P

[sbc100]

Thanks. Sounds like a relatively simple fix!

[starball5]

If this behaviour is documented anywhere, it would be nice for this nuance to be included in the documentation as well.

[robtaylor]

Why was this closed?

[techie-guy]

Why was this closed?

It was solved in this StackOverflow Question

https://stackoverflow.com/q/75594285/11107541

[robtaylor]

Hmm, no, this isn't fixed in general.. shouldn't need to modify cmake to generate the right outcome, should be.a define, or an option to emcmake

…

On Mon, Jul 10, 2023 at 3:06 PM Techie Guy ***@***.***> wrote: Why was this closed? It was solved in this StackOverflow Question https://stackoverflow.com/q/75594285/11107541 — Reply to this email directly, view it on GitHub <#18860 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAB4O4GAJD4SCGCHI5YQ6CDXPP45DANCNFSM6AAAAAAVJWKCTQ> . You are receiving this because you commented.Message ID: ***@***.***>