[SpiderMonkey] exposing internal APIs when embedding into a C++ project?

SpiderMonkey
1

I am trying to create a debug build of SpiderMonkey and load it as a library in a different C++ project while exposing internal APIs like the BytecodeEmitter, etc.

I tried updating the moz.build files:

EXPORTS.frontend += [
  "frontend/AbstractScopePtr.h",
  "frontend/AsyncEmitter.h",
  "frontend/BytecodeCompiler.h",
  "frontend/BytecodeControlStructures.h",
  "frontend/BytecodeEmitter.h",
...

After the build I tried to load up the project

include_directories(
    ${SPIDERMONKEY_OBJ_DIR}/dist/include
)
...
target_link_libraries(metal_monkey PRIVATE
    ${ICU_LIBRARIES}
    /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/js/src/build/libjs_static.a
    z
    dl
    pthread
    stdc++
)

But the build fails with a bunch of linker errors

[100%] Linking CXX executable mmm
/usr/bin/ld: /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/js/src/build/libjs_static.a(Unified_cpp_js_src18.o): in function `mozilla::Array<js::GlobalObjectData::ConstructorWithProto, 95ul>::operator[](unsigned long) const':
/home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/dist/include/mozilla/Array.h:51: undefined reference to `mozilla::detail::InvalidArrayIndex_CRASH(unsigned long, unsigned long)'
/usr/bin/ld: /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/dist/include/mozilla/Array.h:51: undefined reference to `mozilla::detail::InvalidArrayIndex_CRASH(unsigned long, unsigned long)'
/usr/bin/ld: /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/dist/include/mozilla/Array.h:51: undefined reference to `mozilla::detail::InvalidArrayIndex_CRASH(unsigned long, unsigned long)'
/usr/bin/ld: /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/dist/include/mozilla/Array.h:51: undefined reference to `mozilla::detail::InvalidArrayIndex_CRASH(unsigned long, unsigned long)'
/usr/bin/ld: /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/dist/include/mozilla/Array.h:51: undefined reference to `mozilla::detail::InvalidArrayIndex_CRASH(unsigned long, unsigned long)'
/usr/bin/ld: /home/mm/wd/mozilla-unified/obj-debug-x86_64-pc-linux-gnu/js/src/build/libjs_static.a(Unified_cpp_js_src18.o): in function `mozilla::IsUtf8(mozilla::Span<char const, 18446744073709551615ul>)':
...

I know this is not the intended mode of operation but I wanted to experiment a bit with SpiderMonkey without directly modifying the source code, any help is appreciated :slight_smile:

I am a beginner to the project so I apologize for dumb questions :slightly_frowning_face:

2

Symbols are hidden by default. You would need to add JS_PUBLIC_API to everything you’re using, and perhaps some JS_PUBLIC_DATA. That’s probably pretty annoying for experimentation, so you might want to try hacking in a -fvisibility=default flag somewhere, or sticking #pragma GCC visibility push(default) into a header like jstypes.h or js-config.h. (There may be problems with that approach.)

For further information, you may need to post your metal_monkey logo for us to examine, because that sounds like it would look pretty cool.

3

Hey Steve, thanks for the reply. Exposing the functions using JS_PUBLIC_API worked :confetti_ball:. Sadly we dont have a logo for metal monkey (yet) :see_no_evil_monkey: With metal monkey we are looking into experimenting with static analysis of JS code with SpiderMonkey bytecode as the backend.

4

You’re not doing anything wrong—linker errors like these usually mean some required object files (like from mozglue or other Mozilla internal libs) aren’t being linked. Try linking against mozglue as well and make sure you include all dependent static libs SpiderMonkey expects. Also double-check that JS_STATIC_BUILD is defined consistently across your build.