Determine DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR value at compile-time or runtime ?

[Benjamin Golinvaux]

Hello,

I am writing a library using Emscripten and I stumbled on issues related to users using different values for DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR when building our lib.

I was about to add a note that mentions the mandatory usage of -s DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR=1 but I thought it would be more elegant to have the library adapt itself (the client of the library have to build it on their own)

I was wondering if I could somehow introspect the settings at compile time (with a #define macro) to find out the value of this flag or, if no macro is provided, at runtime (worse, but sufficient for my needs)

I think I could use an awful hack where I examine the dom and try to register a dummy event callback and check its value, but I would like to avoid that if possible.

Thanks in advance for any information on this topic.

Benjamin

[A K]

Hi Benjamin,

I would be happy if Emscripten had something like what you propose, but just let me share how we deal with these issues:

If you use cmake then the Emscripten toolchain file defines EMSCRIPTEN_VERSION (https://github.com/emscripten-core/emscripten/blob/ceacba11/cmake/Modules/Platform/Emscripten.cmake#L128), which you can use to direct compilation through cmake=>preprocessor defines. You unfortunately still have to check the changelog or Emscripten history manually to find out when each feature was introduced/changed.

For the find event target behavior change in particular, we have the following in our code:

if (EMSCRIPTEN_VERSION VERSION_GREATER_EQUAL "1.39.5")
    set(EMSCRIPTEN_HAS_NEW_DOM_ELEMENT_LOOKUP_BEHAVIOUR ON)
else()
    set(EMSCRIPTEN_HAS_NEW_DOM_ELEMENT_LOOKUP_BEHAVIOUR OFF)
endif()

Which is later exposed to the C++ preprocessor using configure_file and a #cmakedefine01.

András

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[Benjamin Golinvaux]

Hello András,

Thanks for your reply. Unfortunately (unless I am missing something), even though the version can be checked, previous versions (such as the 1.38.47 I am using) can be used with DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR set to 0 (or unset) or 1.

I was hoping for an extra macro available to the C/C++ preprocessor...

Your tip might be useful in many other situations, though!

Best

[Alon Zakai]

Another option is RETAIN_COMPILER_SETTINGS and then calling emscripten_get_compiler_setting(), see settings.js.

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[Benjamin Golinvaux]

Thank you !   I wasn't aware of this. Very handy.