Hi all! I’m trying to introduce a rust library to ...

# kotlin-native

[SeikoDes]

Hi all! I’m trying to introduce a rust library to KMP, but I don’t know how to configure ios cinterops, I’ve tried to build an xcode project to verify that the .h .a is working, but currently in KMP it prompts:

Undefined symbols for architecture x86_64:
  "_CTFontGetXHeight", referenced from:
      SkScalerContext_Mac::generateFontMetrics(SkFontMetrics*) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
  "_CTFontGetUnderlineThickness", referenced from:
      SkScalerContext_Mac::generateFontMetrics(SkFontMetrics*) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
  "_CTFontGetUnderlinePosition", referenced from:
      SkScalerContext_Mac::generateFontMetrics(SkFontMetrics*) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
  "_CTFontGetAdvancesForGlyphs", referenced from:
      SkScalerContext_Mac::generateMetrics(SkGlyph*, SkArenaAlloc*) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
  "_CTFontCreatePathForGlyph", referenced from:
      SkScalerContext_Mac::generateMetrics(SkGlyph*, SkArenaAlloc*) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
      SkScalerContext_Mac::generatePath(SkGlyph const&, SkPath*) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
  "_CTFontDrawGlyphs", referenced from:
      SkCTFontGetSmoothBehavior() in libskia.a(libskia.SkCTFont.o)
      SkScalerContext_Mac::Offscreen::getCG(SkScalerContext_Mac const&, SkGlyph const&, unsigned short, unsigned long*, bool) in libskia.a(fontmgr_mac_ct.SkScalerContext_mac_ct.o)
  "_kCTFontVariationAxisMinimumValueKey", referenced from:
      SkCTVariationFromSkFontArguments(__CTFont const*, SkFontArguments const&) in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
      SkTypeface_Mac::onGetVariationDesignParameters(SkFontParameters::Variation::Axis*, int) const in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
  "_CTFontGetSize", referenced from:
      ...
  "_CTFontGetSymbolicTraits", referenced from:
      create_from_name(char const*, SkFontStyle const&) in libskia.a(fontmgr_mac_ct.SkFontMgr_mac_ct.o)
      SkTypeface_Mac::Make(std::__1::unique_ptr<__CTFont const, SkFunctionWrapper<void (void const*), &(CFRelease)> >, OpszVariation, std::__1::unique_ptr<SkStreamAsset, std::__1::default_delete<SkStreamAsset> >)::$_0::operator()() const in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
      SkTypeface_Mac::onGetAdvancedMetrics() const in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
  "_kCTFontFamilyNameKey", referenced from:
      SkTypeface_Mac::onCreateFamilyNameIterator() const in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
  "_CTFontCollectionCreateMatchingFontDescriptors", referenced from:
      (anonymous namespace)::SkCopyAvailableFontFamilyNames(__CTFontCollection const*) in libskia.a(fontmgr_mac_ct.SkFontMgr_mac_ct.o)
  "_CTFontCopyAttribute", referenced from:
      SkCTFontCreateExactCopy(__CTFont const*, double, OpszVariation) in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
      SkTypeface_Mac::onOpenStream(int*) const in libskia.a(fontmgr_mac_ct.SkTypeface_mac_ct.o)
  "_CTFontCreateForString", referenced from:
      SkFontMgr_Mac::onMatchFamilyStyleCharacter(char const*, SkFontStyle const&, char const**, int, int) const in libskia.a(fontmgr_mac_ct.SkFontMgr_mac_ct.o)
ld: symbol(s) not found for architecture x86_64

demo: https://github.com/qdsfdhvh/compose-hellorust

[napperley]

Do note that Kotlin Native doesn't provide any Rust interop. Interoperability with Rust isn't supported.

[kpgalligan]

It would if rust exposes C interop, yes?

[napperley]

If rust generates a C compliant API then that would work with Kotlin Native via its C interop. This doesn't automatically mean that Rust interop is supported since that would require direct communication between Kotlin and Rust, without an intermediate API getting in the way.

[kpgalligan]

Well, I mean, I would assume anybody trying to interop with Rust would expose a C interface. AFAIK, that’s the only (reasonable) way to interop with Rust.

[kpgalligan]

That is me making assumptions. Definitely no direct interop.

[kpgalligan]

Looking at the errors, that does look like what the OP is trying to do.

[napperley]

Not surprising since C in some ways acts as a common language for many native/platforms APIs like JS does for web APIs.

[napperley]

I'm not familiar with how Rust generates C APIs. Does Rust only generate header files, or does it generate header and library files (aka traditional C library)?

[napperley]

Looks like the OP hasn't setup the configuration properly for generating the C library from Rust. Some libraries (like LVGL for example - https://docs.lvgl.io/8/porting/project.html#configuration-file ) use configuration to determine which symbols to include in library files (to keep the file size down as much as possible - common in Embedded environments).