Passing a default-conv sx function to a `callconv(.c)` fn-pointer slot
(e.g. pthread_create's start routine) used to silently mismatch ABIs:
the C-side caller didn't supply __sx_ctx, so the sx-side body read its
first user param as garbage. The bug surfaced as a SIGSEGV inside
ANativeWindow_setBuffersGeometry on Android during chess bringup.
Now the compiler rejects the coercion outright at the bare-fn name
lookup site:
error: call-convention mismatch: 'sx_handler' is declared with
default sx convention but the target type expects callconv(.c)
Also: `#foreign` declarations without an explicit `callconv` now default
to `.c` instead of `.default`. Every external C symbol is by definition
C-conv; the previous default silently typed `objc_msgSend` (et al.) as
default-conv, so the check would fire on the consumer side when the
user typed a fn-ptr as `callconv(.c)`. With the foreign-default fix,
the existing typed-msgSend casts in `std/objc.sx` and `gpu/metal.sx`
keep type-checking and the rule is "C-conv on both sides or neither."
Caught by the new check (fixed in the same commit):
- `ios_gl_proc` in `platform/uikit.sx` lacked callconv(.c) but was
passed to `load_gl` whose `get_proc` slot expects it.
- `ffi_apply_callback` / `ffi_apply_callback2` in
`examples/ffi-06-callback.sx` had default-conv fn-ptr params but
the C bodies (in the companion .c) are unambiguously C-conv.
Regression test: `examples/131-callconv-mismatch-diagnostic.sx`
locks in the diagnostic shape (sx-conv fn → callconv(.c) slot).
153/153 example tests pass. Chess green on macOS / iOS sim / Android.
Continues the implicit-Context refactor. Bare-fn trampolines, lambda
trampolines, and protocol thunks now carry __sx_ctx at slot 0; call
sites for closures, fn-pointer variables, and method dispatch prepend
the caller's current ctx.
- emit_llvm.zig:1687 call_indirect treats `fp_ctx_slots` leading args
as opaque ptr (the implicit ctx) when the fn-pointer is default-conv
under has_implicit_ctx.
- lower.zig:fnPtrTypeWantsCtx predicate gates the prepend at both
scope-local and global fn-pointer call sites.
- lower.zig:fixupMethodReceiver skips __sx_ctx when probing the
receiver param's type.
- lower.zig:lowerLambda builds closure type from user-visible params
only (skip ctx + env).
- lower.zig:closure(bare_fn) builds closure type from user-visible
params only.
- module.zig: Module.has_implicit_ctx flag mirrors Lowering's switch
so emit_llvm can read it without a back-pointer.
Tests updated:
- 5 ObjC-block/runtime tests get `callconv(.c)` on fn-ptr types
cast from `objc_msgSend` / Block.invoke (C-side calls into sx).
- ffi-06-callback gets `callconv(.c)` on double_it/add_with_ctx —
the registered C-side callbacks.
- 08-types snapshot regen (undefined-init drift from layout shift).
- 11 JNI/ObjC .ir snapshots regen for the ctx-prepended thunk
signatures.
151/152 example tests pass. Remaining failure (05-run) is the
comptime/interp path that requires Step 7 (callWithDefaultContext).
vendors/ is a third-party namespace (stb_image, kb_text_shape, etc.);
test fixtures don't belong there. The .c/.h companion files for the
Phase-0 FFI baselines now sit alongside the .sx that drives them in
examples/, with matching basenames:
examples/ffi-01-primitives.{sx,c,h} <- was vendors/ffi_primitives/
examples/ffi-02-small-struct.{sx,c,h} <- was vendors/ffi_structs/
examples/ffi-03-large-struct.{sx,c,h} <- was vendors/ffi_large_struct/
examples/ffi-04-fp-struct.{sx,c,h} <- was vendors/ffi_fp_struct/
examples/ffi-05-string-args.{sx,c,h} <- was vendors/ffi_strings/
examples/ffi-06-callback.{sx,c,h} <- was vendors/ffi_callback/
examples/101-ffi-medium-struct.{sx,c} <- was vendors/ffi_medium_struct/
`#source` / `#include` paths in the .sx files become bare filenames
(no prefix) since imports.zig's base_dir resolution finds them
relative to the importing .sx file's directory.
`library/vendors/sx_ffi_resolve_test/` stays put — that one's the
whole point: regression coverage for the stdlib-search branch of
the resolution chain, so it must live where ONLY that branch can
find it.
94/94 regression tests pass.
93/93 regression tests pass (+ffi-06-callback).
Mirrors the `app->onInputEvent` install pattern from
library/modules/platform/android.sx:
1. (s32) -> s32 — single primitive arg/return
2. (*void, s32) -> s32 — opaque ctx pointer + value
(the onInputEvent shape)
Side effects via two file-level globals so the test observes both
the return value AND state mutation across multiple calls:
- g_callback_hits = N proves the callback fired N times.
- g_callback_sum = sum of args proves each individual call landed
with the correct value.
The ctx-pointer variant casts `*void` back to `*s32` inside the
callback and reads through it (`p.*`), proving the pointer survives
the round-trip with no aliasing weirdness.
