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Work around alloca(3) in fun_bc_call(). #13

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Merged
ltratt merged 1 commit into from
Mar 31, 2026
Merged

Work around alloca(3) in fun_bc_call(). #13

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18 changes: 18 additions & 0 deletions py/objfun.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,9 @@

#include <string.h>
#include <assert.h>
#ifdef USE_YK
#include <stdlib.h>
#endif

#include "py/emitglue.h"
#include "py/objcode.h"
Expand Down Expand Up @@ -270,7 +273,18 @@ static mp_obj_t fun_bc_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const
#if MICROPY_ENABLE_PYSTACK
code_state = mp_pystack_alloc(offsetof(mp_code_state_t, state) + state_size);
#else
#ifdef USE_YK
// Avoid alloca(3) when using yk.
//
// Fucntions that use alloca(3) cannot be traced because stackmaps don't
// work on dynamically-sized frames.
//
// Instead of storing "small" code states on the stack (using alloca), we
// therefore store *all* code states on the GC heap.
{
#else
if (state_size > VM_MAX_STATE_ON_STACK) {
#endif
code_state = m_new_obj_var_maybe(mp_code_state_t, state, byte, state_size);
#if MICROPY_DEBUG_VM_STACK_OVERFLOW
if (code_state != NULL) {
Expand All @@ -279,11 +293,15 @@ static mp_obj_t fun_bc_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const
#endif
}
if (code_state == NULL) {
#ifdef USE_YK
abort(); // we must have heap allocated
#else
code_state = alloca(offsetof(mp_code_state_t, state) + state_size);
#if MICROPY_DEBUG_VM_STACK_OVERFLOW
memset(code_state->state, 0, state_size);
#endif
state_size = 0; // indicate that we allocated using alloca
#endif
}
#endif

Expand Down