How to use Hermes

[gabriel-earle]

Thanks a ton for a wonderful package. What are the steps I can use to choose Hermes as the JS engine?

Gabe

[shih1]

I had to add configs to the Preprocessor Definitions and Header Search Paths recently to get hermes to work

Preprocessor

REACTJUCE_USE_HERMES=1

Headers

**/react-juce/react_juce/hermes/API/
**/react-juce/react_juce/hermes/public/
**/react-juce/react_juce/hermes/API/jsi/

Header locations will change depending on system.

[gabriel-earle]

Thank you!! I was able to actually figure it out with the help of ChatGPT 4. It was able to scan this Repo using the browser, use its deep knowledge of C++, a tiny bit of knowledge of Hermes, and everything else to help me get to a solution. I am also compiling through Projucer so that added a ton of work. CMake is probably a better choice if using Hermes, but if anyone stumbles upon this who is using Projucer, you'll need to do the following:

• build Hermes manually. It's not too hard, just compile using the python script in utils/build, and then build by changing directory to the build directory that was created and using ninja.
• In Projucer, in your Exporter settings, add all of these to "external libraries to link". Each one of these is a part of hermes that corresponds to one lib file (ie hermesSupport corresponds to libhermesSupport.a):

  hermesapi
  hermesSupport
  hermesVMRuntime
  hermesADT
  hermesPlatform
  hermesPlatformUnicode
  hermesBackend
  hermesHBCBackend
  hermesFrontend
  hermesOptimizer
  hermesSourceMap
  hermesFrontEndDefs
  hermesAST
  hermesInst
  hermesRegex
  hermesParser
  LLVHSupport
  jsi
  dtoa

• Then in your target (I've only done debug so far), add all of the "external library search paths". These are just the directories that directly contain each of the lib files above. I’ve only tested it as an absolute path. I'm just gonna cut everything off before the hermes submodule for simplicity.

  hermes/utils/build/build/API/hermes
  hermes/utils/build/build/lib/Support
  hermes/utils/build/build/lib/VM
  hermes/utils/build/build/lib/ADT
  hermes/utils/build/build/lib/Platform
  hermes/utils/build/build/lib/Platform/Unicode
  hermes/utils/build/build/lib/BCGen
  hermes/utils/build/build/lib/BCGen/HBC
  hermes/utils/build/build/lib
  hermes/utils/build/build/lib/SourceMap
  hermes/utils/build/build/lib/FrontEndDefs
  hermes/utils/build/build/lib/AST
  hermes/utils/build/build/lib/Inst
  hermes/utils/build/build/lib/Regex
  hermes/utils/build/build/lib/Parser
  hermes/utils/build/build/jsi
  hermes/utils/build/build/external/llvh/lib/Support
  hermes/utils/build/build/external/dtoa