b7ec44e82b
CL 157557 changes the compiler to add one byte padding to
non-empty struct ending with a zero-sized field. Add the same
padding to the FFI type, so reflect.Call works.
This fixes test/fixedbugs/issue26335.go in the main repo.
Reviewed-on: https://go-review.googlesource.com/c/158018
From-SVN: r267956
368 lines
8.6 KiB
Go
368 lines
8.6 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Only build this file if libffi is supported.
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// +build libffi
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package runtime
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import "unsafe"
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// This file contains the code that converts a Go type to an FFI type.
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// This has to be written in Go because it allocates memory in the Go heap.
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// C functions to return pointers to libffi variables.
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func ffi_type_pointer() *__ffi_type
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func ffi_type_sint8() *__ffi_type
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func ffi_type_sint16() *__ffi_type
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func ffi_type_sint32() *__ffi_type
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func ffi_type_sint64() *__ffi_type
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func ffi_type_uint8() *__ffi_type
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func ffi_type_uint16() *__ffi_type
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func ffi_type_uint32() *__ffi_type
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func ffi_type_uint64() *__ffi_type
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func ffi_type_float() *__ffi_type
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func ffi_type_double() *__ffi_type
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func ffi_supports_complex() bool
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func ffi_type_complex_float() *__ffi_type
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func ffi_type_complex_double() *__ffi_type
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func ffi_type_void() *__ffi_type
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// C functions defined in libffi.
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//extern ffi_prep_cif
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func ffi_prep_cif(*_ffi_cif, _ffi_abi, uint32, *__ffi_type, **__ffi_type) _ffi_status
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// ffiFuncToCIF is called from C code.
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//go:linkname ffiFuncToCIF runtime.ffiFuncToCIF
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// ffiFuncToCIF builds an _ffi_cif struct for function described by ft.
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func ffiFuncToCIF(ft *functype, isInterface bool, isMethod bool, cif *_ffi_cif) {
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nparams := len(ft.in)
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nargs := nparams
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if isInterface {
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nargs++
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}
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args := make([]*__ffi_type, nargs)
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i := 0
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off := 0
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if isInterface {
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args[0] = ffi_type_pointer()
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off = 1
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} else if isMethod {
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args[0] = ffi_type_pointer()
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i = 1
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}
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for ; i < nparams; i++ {
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args[i+off] = typeToFFI(ft.in[i])
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}
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rettype := funcReturnFFI(ft)
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var pargs **__ffi_type
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if len(args) > 0 {
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pargs = &args[0]
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}
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status := ffi_prep_cif(cif, _FFI_DEFAULT_ABI, uint32(nargs), rettype, pargs)
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if status != _FFI_OK {
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throw("ffi_prep_cif failed")
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}
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}
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// funcReturnFFI returns the FFI definition of the return type of ft.
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func funcReturnFFI(ft *functype) *__ffi_type {
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c := len(ft.out)
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if c == 0 {
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return ffi_type_void()
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}
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// Compile a function that returns a zero-sized value as
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// though it returns void. This works around a problem in
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// libffi: it can't represent a zero-sized value.
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var size uintptr
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for _, v := range ft.out {
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size += v.size
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}
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if size == 0 {
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return ffi_type_void()
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}
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if c == 1 {
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return typeToFFI(ft.out[0])
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}
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elements := make([]*__ffi_type, c+1)
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for i, v := range ft.out {
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elements[i] = typeToFFI(v)
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}
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elements[c] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// typeToFFI returns the __ffi_type for a Go type.
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func typeToFFI(typ *_type) *__ffi_type {
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switch typ.kind & kindMask {
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case kindBool:
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switch unsafe.Sizeof(false) {
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case 1:
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return ffi_type_uint8()
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case 4:
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return ffi_type_uint32()
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default:
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throw("bad bool size")
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return nil
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}
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case kindInt:
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return intToFFI()
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case kindInt8:
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return ffi_type_sint8()
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case kindInt16:
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return ffi_type_sint16()
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case kindInt32:
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return ffi_type_sint32()
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case kindInt64:
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return ffi_type_sint64()
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case kindUint:
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switch unsafe.Sizeof(uint(0)) {
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case 4:
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return ffi_type_uint32()
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case 8:
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return ffi_type_uint64()
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default:
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throw("bad uint size")
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return nil
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}
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case kindUint8:
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return ffi_type_uint8()
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case kindUint16:
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return ffi_type_uint16()
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case kindUint32:
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return ffi_type_uint32()
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case kindUint64:
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return ffi_type_uint64()
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case kindUintptr:
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switch unsafe.Sizeof(uintptr(0)) {
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case 4:
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return ffi_type_uint32()
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case 8:
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return ffi_type_uint64()
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default:
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throw("bad uinptr size")
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return nil
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}
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case kindFloat32:
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return ffi_type_float()
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case kindFloat64:
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return ffi_type_double()
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case kindComplex64:
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if ffi_supports_complex() {
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return ffi_type_complex_float()
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} else {
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return complexToFFI(ffi_type_float())
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}
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case kindComplex128:
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if ffi_supports_complex() {
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return ffi_type_complex_double()
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} else {
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return complexToFFI(ffi_type_double())
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}
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case kindArray:
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return arrayToFFI((*arraytype)(unsafe.Pointer(typ)))
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case kindChan, kindFunc, kindMap, kindPtr, kindUnsafePointer:
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// These types are always simple pointers, and for FFI
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// purposes nothing else matters.
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return ffi_type_pointer()
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case kindInterface:
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return interfaceToFFI()
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case kindSlice:
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return sliceToFFI((*slicetype)(unsafe.Pointer(typ)))
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case kindString:
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return stringToFFI()
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case kindStruct:
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return structToFFI((*structtype)(unsafe.Pointer(typ)))
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default:
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throw("unknown type kind")
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return nil
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}
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}
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// interfaceToFFI returns an ffi_type for a Go interface type.
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// This is used for both empty and non-empty interface types.
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func interfaceToFFI() *__ffi_type {
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elements := make([]*__ffi_type, 3)
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elements[0] = ffi_type_pointer()
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elements[1] = elements[0]
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elements[2] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// stringToFFI returns an ffi_type for a Go string type.
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func stringToFFI() *__ffi_type {
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elements := make([]*__ffi_type, 3)
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elements[0] = ffi_type_pointer()
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elements[1] = intToFFI()
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elements[2] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// structToFFI returns an ffi_type for a Go struct type.
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func structToFFI(typ *structtype) *__ffi_type {
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c := len(typ.fields)
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if c == 0 {
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return emptyStructToFFI()
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}
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fields := make([]*__ffi_type, 0, c+1)
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checkPad := false
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lastzero := false
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for i, v := range typ.fields {
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// Skip zero-sized fields; they confuse libffi,
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// and there is no value to pass in any case.
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// We do have to check whether the alignment of the
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// zero-sized field introduces any padding for the
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// next field.
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if v.typ.size == 0 {
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checkPad = true
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lastzero = true
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continue
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}
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lastzero = false
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if checkPad {
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off := uintptr(0)
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for j := i - 1; j >= 0; j-- {
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if typ.fields[j].typ.size > 0 {
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off = typ.fields[j].offset() + typ.fields[j].typ.size
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break
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}
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}
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off += uintptr(v.typ.align) - 1
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off &^= uintptr(v.typ.align) - 1
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if off != v.offset() {
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fields = append(fields, padFFI(v.offset()-off))
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}
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checkPad = false
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}
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fields = append(fields, typeToFFI(v.typ))
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}
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if lastzero {
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// The compiler adds one byte padding to non-empty struct ending
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// with a zero-sized field (types.cc:get_backend_struct_fields).
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// Add this padding to the FFI type.
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fields = append(fields, ffi_type_uint8())
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}
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fields = append(fields, nil)
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &fields[0],
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}
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}
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// sliceToFFI returns an ffi_type for a Go slice type.
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func sliceToFFI(typ *slicetype) *__ffi_type {
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elements := make([]*__ffi_type, 4)
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elements[0] = ffi_type_pointer()
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elements[1] = intToFFI()
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elements[2] = elements[1]
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elements[3] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// complexToFFI returns an ffi_type for a Go complex type.
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// This is only used if libffi does not support complex types internally
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// for this target.
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func complexToFFI(ffiFloatType *__ffi_type) *__ffi_type {
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elements := make([]*__ffi_type, 3)
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elements[0] = ffiFloatType
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elements[1] = ffiFloatType
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elements[2] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// arrayToFFI returns an ffi_type for a Go array type.
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func arrayToFFI(typ *arraytype) *__ffi_type {
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if typ.len == 0 {
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return emptyStructToFFI()
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}
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elements := make([]*__ffi_type, typ.len+1)
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et := typeToFFI(typ.elem)
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for i := uintptr(0); i < typ.len; i++ {
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elements[i] = et
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}
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elements[typ.len] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// intToFFI returns an ffi_type for the Go int type.
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func intToFFI() *__ffi_type {
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switch unsafe.Sizeof(0) {
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case 4:
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return ffi_type_sint32()
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case 8:
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return ffi_type_sint64()
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default:
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throw("bad int size")
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return nil
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}
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}
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// emptyStructToFFI returns an ffi_type for an empty struct.
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// The libffi library won't accept a struct with no fields.
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func emptyStructToFFI() *__ffi_type {
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elements := make([]*__ffi_type, 2)
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elements[0] = ffi_type_void()
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elements[1] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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// padFFI returns a padding field of the given size
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func padFFI(size uintptr) *__ffi_type {
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elements := make([]*__ffi_type, size+1)
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for i := uintptr(0); i < size; i++ {
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elements[i] = ffi_type_uint8()
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}
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elements[size] = nil
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return &__ffi_type{
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_type: _FFI_TYPE_STRUCT,
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elements: &elements[0],
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}
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}
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//go:linkname makeCIF reflect.makeCIF
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// makeCIF is used by the reflect package to allocate a CIF.
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func makeCIF(ft *functype) *_ffi_cif {
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cif := new(_ffi_cif)
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ffiFuncToCIF(ft, false, false, cif)
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return cif
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}
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