There are several places in the Stylo FFI boundary where one side thinks it's returning a struct and other side sees something else. With the Linux32 ABI, this causes havoc because returned structs are expected to allocated on the caller's stack and passed as a pointer before all the real arguments. If one side disagrees, then arguments will all be off by one.

Comment on attachment 8897648 [details] Bug 1390691 - Fix up Servo_StyleSet_Init for Linux 32-bit ABI. https://reviewboard.mozilla.org/r/168916/#review174272

Comment on attachment 8897649 [details] Bug 1390691 - Fix up Gecko_CalcStyleDifference for Linux 32-bit ABI. https://reviewboard.mozilla.org/r/168918/#review174274 ::: layout/style/ServoBindings.h:399 (Diff revision 1) > // Not if we do them in Gecko... > nsStyleContext* Gecko_GetStyleContext(RawGeckoElementBorrowed element, > nsIAtom* aPseudoTagOrNull); > mozilla::CSSPseudoElementType Gecko_GetImplementedPseudo(RawGeckoElementBorrowed element); > -nsChangeHint Gecko_CalcStyleDifference(ServoStyleContextBorrowed old_style, > +// We'd like to return `nsChangeHint` here, but bindgen bitfield enums don't > +// work as return values with the Linux 32-bit ABI at the moment because :(

Comment on attachment 8897650 [details] Bug 1390691 - Fix up Servo_TakeChangeHint for Linux 32-bit ABI. https://reviewboard.mozilla.org/r/168920/#review174276

Comment on attachment 8897651 [details] Bug 1390691 - Fix up Servo_StyleSet_MediumFeaturesChanged for Linux 32-bit ABI. https://reviewboard.mozilla.org/r/168922/#review174278 ::: servo/ports/geckolib/glue.rs:903 (Diff revision 1) > > #[no_mangle] > pub extern "C" fn Servo_StyleSet_MediumFeaturesChanged( > raw_data: RawServoStyleSetBorrowed, > viewport_units_used: *mut bool, > -) -> OriginFlags { > +) -> u8 { could you change the type on the gecko side too? otherwise this will fail `./mach test-stylo`

Comment on attachment 8897651 [details] Bug 1390691 - Fix up Servo_StyleSet_MediumFeaturesChanged for Linux 32-bit ABI. https://reviewboard.mozilla.org/r/168922/#review174278 > could you change the type on the gecko side too? otherwise this will fail `./mach test-stylo` Good catch, I fixed these up and verified the tests pass (at least as well they did before on Linux32).

Pushed by jryans@gmail.com: https://hg.mozilla.org/integration/autoland/rev/7c30ae9302d7 Fix up Servo_StyleSet_Init for Linux 32-bit ABI. r=manishearth https://hg.mozilla.org/integration/autoland/rev/fa23649e8468 Fix up Gecko_CalcStyleDifference for Linux 32-bit ABI. r=manishearth https://hg.mozilla.org/integration/autoland/rev/6451e509bea1 Fix up Servo_TakeChangeHint for Linux 32-bit ABI. r=manishearth https://hg.mozilla.org/integration/autoland/rev/5ffa205aea21 Fix up Servo_StyleSet_MediumFeaturesChanged for Linux 32-bit ABI. r=manishearth

https://hg.mozilla.org/mozilla-central/rev/7c30ae9302d7 https://hg.mozilla.org/mozilla-central/rev/fa23649e8468 https://hg.mozilla.org/mozilla-central/rev/6451e509bea1 https://hg.mozilla.org/mozilla-central/rev/5ffa205aea21