Module host_fns 

Enums

RuntimeError

Runtime errors raised by JIT code via host functions.

Functions

clear_gc_state

Clear the active GC state for the current thread.

clear_gc_test_hook

Clear the GC test hook.

clear_stack_map_registry

Clear the stack map registry for the current thread.

debug_app_check^⚠

Returns 0 if the call is safe to proceed, or a poison pointer if the call should be short-circuited (runtime error already set or call depth exceeded).

drain_diagnostics

Drain all accumulated diagnostics.

error_poison_ptr

Return a pointer to a pre-allocated “poison” Closure heap object. When JIT code tries to call this as a function, it returns itself, preventing cascading crashes. The runtime error flag is already set, so the effect machine will catch it before the poison reaches user code.

error_poison_ptr_lazy

Return a pre-allocated “lazy poison” Closure for a given error kind. Unlike error_poison_ptr(), this does NOT set the error flag at creation time. The error is only triggered when the closure is actually called (via poison_trampoline_lazy). This is critical for typeclass dictionaries where error methods exist as fields but may never be invoked.

error_poison_ptr_lazy_msg

Create a pre-allocated “lazy poison” Closure for a given error kind and message.

gc_trigger

GC trigger: called by JIT code when alloc_ptr exceeds alloc_limit.

gc_trigger_call_count

Get gc_trigger call count. Only call from tests.

gc_trigger_last_vmctx

Get last vmctx passed to gc_trigger. Only call from tests.

get_exec_context

Get the current execution context.

heap_force

Force a thunk to WHNF. Loops to handle chains (thunk returning thunk).

host_fn_symbols

last_gc_roots

Get collected roots from the last gc_trigger call.

push_diagnostic

Push a diagnostic message to the thread-local buffer.

reset_call_depth

Reset the call depth counter. Call before each JIT invocation.

reset_test_counters

Reset test counters. Only call from tests.

runtime_bad_thunk_state_trap

Called by JIT code when a Thunk has an invalid state.

runtime_blackhole_trap

Called by JIT code when a BlackHole is encountered (thunk forcing itself).

runtime_cas_boxed_array

CAS on a boxed array slot: compare-and-swap arr[idx]. Returns the old value. If old == expected, writes new.

runtime_case_trap

Debug: called instead of trap user2 when TIDEPOOL_DEBUG_CASE is set. Prints diagnostic info about the scrutinee that failed case matching. scrut_ptr is the heap pointer to the scrutinee. num_alts is the number of data alt tags expected. alt_tags is a pointer to an array of expected tag u64 values.

runtime_clone_boxed_array

Clone a sub-range of a boxed array: src[off..off+len].

runtime_compare_byte_arrays

Compare byte arrays: returns -1, 0, or 1.

runtime_copy_addr_to_byte_array

Copy len bytes from src (Addr#) to dest_ba (ByteArray ptr) at dest_off.

runtime_copy_boxed_array

Copy len pointer slots from src[src_off..] to dest[dest_off..].

runtime_copy_byte_array

Copy len bytes between byte arrays: src[src_off..] -> dest[dest_off..]. Used by both copyByteArray# and copyMutableByteArray#.

runtime_decode_double_exponent

Decode a Double into its Int exponent.

runtime_decode_double_mantissa

Decode a Double into its Int64 mantissa (significand). GHC’s decodeDouble_Int64# returns (# mantissa, exponent #).

runtime_double_acos

runtime_double_acosh

runtime_double_asin

runtime_double_asinh

runtime_double_atan

runtime_double_atanh

runtime_double_cos

runtime_double_cosh

runtime_double_exp

runtime_double_expm1

runtime_double_log

runtime_double_log1p

runtime_double_power

runtime_double_sin

runtime_double_sinh

runtime_double_tan

runtime_double_tanh

runtime_error

Called by JIT code for runtime errors (divZeroError, overflowError). Sets a thread-local error flag and returns a “poison” Lit(Int#, 0) object instead of null. This prevents JIT code from segfaulting on the return value. The effect machine checks the error flag after JIT returns and converts to Yield::Error. kind: 0 = divZeroError, 1 = overflowError, 2 = UserError, 3 = Undefined

runtime_error_with_msg

Called by JIT code for runtime errors with a specific message.

runtime_new_boxed_array

Allocate a new boxed array of len pointer slots, each initialized to init. Layout: [u64 length][ptr0][ptr1]…[ptrN-1] Each slot is 8 bytes (a heap pointer).

runtime_new_byte_array

Allocate a new mutable byte array of size bytes, zeroed. Layout: [u64 length][u8 bytes…] Returns a raw pointer to the allocation (caller stores in Lit value slot).

runtime_oom

runtime_resize_byte_array

Resize a mutable byte array. Allocates a new buffer, copies existing data, zeroes any new bytes, and frees the old buffer. Returns the new pointer.

runtime_set_byte_array

Set len bytes in ba starting at off to val.

runtime_show_double_addr

Format a Double as a null-terminated C string and return its address. The CString is leaked (small bounded strings, acceptable).

runtime_shrink_boxed_array

Shrink a boxed array (just update the length field).

runtime_shrink_byte_array

Shrink a mutable byte array to new_size bytes (just updates the length prefix).

runtime_strlen

strlen: count bytes until null terminator.

runtime_text_measure_off

Measure codepoints in a UTF-8 buffer. Matches text-2.1.2 _hs_text_measure_off semantics.

runtime_text_memchr

Find a byte in a buffer. Returns offset from start, or -1 if not found.

runtime_text_reverse

Reverse UTF-8 text. Matches text-2.1.2 _hs_text_reverse(dst0, src0, off, len).

set_exec_context

Set the current execution context for JIT code. This is used to provide more info when a signal (SIGSEGV/SIGILL) occurs.

set_gc_state

Set the active GC state for the current thread.

set_gc_test_hook

Set a hook to be called during gc_trigger with the collected roots.

set_stack_map_registry

Set the stack map registry for the current thread.

take_runtime_error

Check and take any pending runtime error from JIT code.

trampoline_resolve

Resolve pending tail calls from VMContext. Called by non-tail App sites when the callee returned null (indicating a tail call was stored).

unresolved_var_trap

Called by JIT code when an unresolved external variable is forced. Returns null to allow execution to continue (will likely segfault later). In debug mode (TIDEPOOL_TRACE), logs and returns null.