building with ninja and looking closely at the output revealed what's
going on. [1] is the output with two `--embed-file path` linker flags
appended to `CMAKE_EXE_LINKER_FLAGS`, and [2] is the output for the same
done with `target_link_options`. as you can see, [2] clubs both of them
together but emcc expected `--embed-file` to just have one argument (if i
can call it that). my mistake was that i didn't read the output carefully
(i was rushing towards the solution <-- real mistake). what i did to "fix"
this was to add quotes around `--embed-file ..@..` linker flags, the quotes
made it to the final command [3]. i thought in cmake everything (arguments)
is a string, so adding quotes won't hurt.
so now i have to figure out how to pass multiple --embed-file flags to the
linker. each tutorial's executable in [0] has it's own assets + the
project's assets, so i need atleast two --embed-file flags. searching and
reading a bit on the internet, i found [-1] i.e. one can pass a flag as
"SHELL:..." and the flag would be passed as a shell string. [-2] explains
it well. it works!
about ninja, it's cool! i tried looked on the internet ways to set ninja as
the default generator inside the cmake file (so that i don't have to use
-G). all i could find was that i can set CMAKE_GENERATOR environment
variable. i then thought of editing the environment varialbe from the cmake
file, but that didn't do anything `set(ENV{CMAKE_GENERATOR} "Ninja")`. so
for now am setting it in the zshrc.
[-2]:
https://gitlab.kitware.com/cmake/cmake/-/merge_requests/1841/diffs?commit_id=ce0b9832163624291db04d38984c6aa7ea8ca7d7
[-1]: https://gitlab.kitware.com/cmake/cmake/-/issues/15826#note_386473
[0]: https://git.kescher.at/printfdebugging/learnopengl
[1]:
```
[79/79] : && /usr/lib/emscripten/emcc -sMAX_WEBGL_VERSION=2
-sNO_DISABLE_EXCEPTION_CATCHING -sASSERTIONS=1 -sWASM=1 -sSAFE_HEAP=1
--embed-file
/home/printfdebugging/repos/learnopengl/source/tutorials/hello-triangle/assets@LearnOpenGL/hello-triangle/assets/
--embed-file
/home/printfdebugging/repos/learnopengl/assets@LearnOpenGL/assets/ -lGL
--js-library
/home/printfdebugging/repos/learnopengl/libs/emscripten-glfw/src/js/lib_emscripten_glfw3.js
source/tutorials/hello-triangle/CMakeFiles/hello-triangle.dir/source/main.c.o
-o source/tutorials/hello-triangle/hello-triangle.html
source/core/libcore.a source/loader/libloader.a libs/glad/libglad.a
libs/emscripten-glfw/libglfw3.a libs/cglm/libcglm.a
cmake/stb/libstb_image.a cmake/stb/libstb_include.a && :
```
[2]:
```
[79/79] : && /usr/lib/emscripten/emcc -sMAX_WEBGL_VERSION=2
-sNO_DISABLE_EXCEPTION_CATCHING -sASSERTIONS=1 -sWASM=1 -sSAFE_HEAP=1
--embed-file
/home/printfdebugging/repos/learnopengl/assets@LearnOpenGL/assets/
/home/printfdebugging/repos/learnopengl/source/tutorials/hello-triangle/assets@LearnOpenGL/hello-triangle/assets/
-lGL --js-library
/home/printfdebugging/repos/learnopengl/libs/emscripten-glfw/src/js/lib_emscripten_glfw3.js
source/tutorials/hello-triangle/CMakeFiles/hello-triangle.dir/source/main.c.o
-o source/tutorials/hello-triangle/hello-triangle.html
source/core/libcore.a source/loader/libloader.a libs/glad/libglad.a
libs/emscripten-glfw/libglfw3.a libs/cglm/libcglm.a
cmake/stb/libstb_image.a cmake/stb/libstb_include.a && :
FAILED: [code=1] source/tutorials/hello-triangle/hello-triangle.html
: && /usr/lib/emscripten/emcc -sMAX_WEBGL_VERSION=2
-sNO_DISABLE_EXCEPTION_CATCHING -sASSERTIONS=1 -sWASM=1 -sSAFE_HEAP=1
--embed-file
/home/printfdebugging/repos/learnopengl/assets@LearnOpenGL/assets/
/home/printfdebugging/repos/learnopengl/source/tutorials/hello-triangle/assets@LearnOpenGL/hello-triangle/assets/
-lGL --js-library
/home/printfdebugging/repos/learnopengl/libs/emscripten-glfw/src/js/lib_emscripten_glfw3.js
source/tutorials/hello-triangle/CMakeFiles/hello-triangle.dir/source/main.c.o
-o source/tutorials/hello-triangle/hello-triangle.html
source/core/libcore.a source/loader/libloader.a libs/glad/libglad.a
libs/emscripten-glfw/libglfw3.a libs/cglm/libcglm.a
cmake/stb/libstb_image.a cmake/stb/libstb_include.a && :
emcc: error:
/home/printfdebugging/repos/learnopengl/source/tutorials/hello-triangle/assets@LearnOpenGL/hello-triangle/assets/:
No such file or directory
("/home/printfdebugging/repos/learnopengl/source/tutorials/hello-triangle/assets@LearnOpenGL/hello-triangle/assets/"
was expected to be an input file, based on the commandline arguments
provided)
ninja: build stopped: subcommand failed.
```
[3]:
```
[79/79] : && /usr/lib/emscripten/emcc -sMAX_WEBGL_VERSION=2
-sNO_DISABLE_EXCEPTION_CATCHING -sASSERTIONS=1 -sWASM=1 -sSAFE_HEAP=1
"--embed-file
/home/printfdebugging/repos/learnopengl/assets@LearnOpenGL/assets/"
"--embed-file
/home/printfdebugging/repos/learnopengl/source/tutorials/hello-triangle/assets@LearnOpenGL/hello-triangle/assets/"
-lGL --js-library
/home/printfdebugging/repos/learnopengl/libs/emscripten-glfw/src/js/lib_emscripten_glfw3.js
source/tutorials/hello-triangle/CMakeFiles/hello-triangle.dir/source/main.c.o
-o source/tutorials/hello-triangle/hello-triangle.html
source/core/libcore.a source/loader/libloader.a libs/glad/libglad.a
libs/emscripten-glfw/libglfw3.a libs/cglm/libcglm.a
cmake/stb/libstb_image.a cmake/stb/libstb_include.a && :
```
On Tuesday, December 16, 2025 at 1:04:25 AM UTC+5:30 [email protected] wrote:
> On Mon, Dec 15, 2025 at 11:28 AM Sahil Gautam <[email protected]>
> wrote:
>
>> the linker flags are indeed passed in both of them, but the loader module
>> throws an error "LearnOpenGL/hello-triangle/shaders/shader.vert" file not
>> found. i use make on linux and ninja on windows though i see your point,
>> ninja is significantly faster. am using `--embed-file` now, thanks sam!
>>
>
> The other reason I recommend ninja so strongly is that it shows the
> failing sub commands. cmake + make will hide the commands from you, even
> when they fail, which causes a lot of annoying back and forth on our bug
> tracker :)
>
> regards
>> sahil gautam
>>
>> On 12/15/25 11:50 PM, 'Sam Clegg' via emscripten-discuss wrote:
>>
>> `target_link_options` should certainly work, and `CMAKE_EXE_LINKER_FLAGS`
>> will also work (the downside is that it applies to all executables).
>>
>> Can you build with `ninja -v` or `make VERBOSE=1` so you can see the full
>> link command that is being used (if you are not using ninja yet I recommend
>> switching right away).
>>
>> You can then easily see if the `--preload-file` argument is passed to the
>> linker or not.
>>
>> Also, I highly recommend using `--embed-file` over `--preload-file`
>> unless you have a specific reason not to. Embedding files in the binary
>> in more efficient in several ways.
>>
>> cheers,
>> sam
>>
>>
>>
>> On Sun, Dec 14, 2025 at 4:23 PM Sahil Gautam <[email protected]>
>> wrote:
>>
>>> hi, i have been putting together an opengl application and recently i
>>> got to know about Emscripten and wasm, so i got to work to add support for
>>> wasm. i got most of the things working thanks to the demo[2]. most of the
>>> examples (in [2] and elsewhere on the internet) append to
>>> `CMAKE_EXE_LINKER_FLAGS` the wasm specific linker flags including
>>> `--preload-file ... `. i read somewhere while learning cmake "we shouldn't
>>> modify CMAKE_EXE_LINKER_FLAGS directly".. don't remember where i read that.
>>>
>>> so i tried using `target_link_options` but the files don't load and the
>>> .data file isn't created either. i wonder if there's a better way to set
>>> these flags than directly appending to CMAKE_EXE_LINKER_FLAGS and i also
>>> wonder why target_link_options doesn't work.
>>>
>>> i will really appreciate some help. i asked this question on an old
>>> github issue [3] as well, then got the idea of writing to the mailing list.
>>>
>>> regards
>>> sahil gautam
>>>
>>> [1]: https://codeberg.org/printfdebugging/learnopengl
>>> [2]:
>>> https://github.com/pongasoft/emscripten-glfw/blob/master/test/demo/CMakeLists.txt
>>> [3]:
>>> https://github.com/emscripten-core/emscripten/issues/4398#issuecomment-3652385357
>>> --
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>>> .
>>>
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