purego: fix cgo fallback build for linux/mips (#462)

Package purego failed to compile under CGO_ENABLED=1 for the Linux
GOARCHs that lack a per-architecture struct file (mips, mipsle,
mips64, mips64le). func.go and syscall.go reference helpers
(addStruct, getStruct, shouldBundleStackArgs, collectStackArgs,
bundleStackArgs, syscall_syscallN) that are only defined for the
natively supported architectures, so the documented integer-only
cgo fallback was broken for these targets.

Add struct_other.go, providing those struct helpers as panicking
stubs for architectures that have no dedicated struct_<arch>.go,
and add the syscall_syscallN stub to syscall_cgo_linux.go.
struct_386.go was already a pure stub, so it is removed and 386
now shares struct_other.go. Structs and floats remain unsupported,
exactly as the README's "Cgo Fallback" section documents.

Add a CI step that cross-compiles linux/mips with CGO_ENABLED=1 to
guard against this regression.

Closes #460

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

commit: 12ee364b5d17bb94d0f5e22976c5a3a6e7c74a8f
author: Hajime Hoshi · 4mo ago · 2026-06-16 03:35 UTC
committer: GitHub · 4mo ago · 2026-06-16 03:35 UTC
parent: d339eb0
signature: GPG UnverifiedB5690EEEBB952194 The key is unknown

4 files · +59 -52

M .github/workflows/test.yml +8 -0


@@ -83,6 +83,14 @@ jobs:
83	83		env GOOS=linux GOARCH=ppc64le go build -v ./...
84	84		env GOOS=linux GOARCH=riscv64 go build -v ./...
85	85
	86	+	- name: go build (Linux mips, Cgo)
	87	+	# mips builds only via the Cgo fallback (CGO_ENABLED=1). See #460.
	88	+	if: runner.os == 'Linux'
	89	+	run: \|
	90	+	sudo apt-get update
	91	+	sudo apt-get install -y gcc-mips-linux-gnu
	92	+	env GOOS=linux GOARCH=mips CGO_ENABLED=1 CC=mips-linux-gnu-gcc go build -v ./...
	93	+
86	94		- name: go build (plugin)
87	95		if: runner.os == 'Linux' \|\| runner.os == 'macOS'
88	96		run:


@@ -83,6 +83,14 @@ jobs:
83	env GOOS=linux GOARCH=ppc64le go build -v ./...	83		env GOOS=linux GOARCH=ppc64le go build -v ./...
84	env GOOS=linux GOARCH=riscv64 go build -v ./...	84		env GOOS=linux GOARCH=riscv64 go build -v ./...
85		85
		86	+	- name: go build (Linux mips, Cgo)
		87	+	# mips builds only via the Cgo fallback (CGO_ENABLED=1). See #460.
		88	+	if: runner.os == 'Linux'
		89	+	run: \|
		90	+	sudo apt-get update
		91	+	sudo apt-get install -y gcc-mips-linux-gnu
		92	+	env GOOS=linux GOARCH=mips CGO_ENABLED=1 CC=mips-linux-gnu-gcc go build -v ./...
		93	+
86	- name: go build (plugin)	94		- name: go build (plugin)
87	if: runner.os == 'Linux' \|\| runner.os == 'macOS'	95		if: runner.os == 'Linux' \|\| runner.os == 'macOS'
88	run:	96		run:

D struct_386.go +0 -52

@@ -1,52 +0,0 @@
1	-	// SPDX-License-Identifier: Apache-2.0
2	-	// SPDX-FileCopyrightText: 2025 The Ebitengine Authors
3	-
4	-	package purego
5	-
6	-	import (
7	-	"reflect"
8	-	"unsafe"
9	-	)
10	-
11	-	func addStruct(v reflect.Value, numInts, numFloats, numStack *int, addInt, addFloat, addStack func(uintptr), keepAlive []any) []any {
12	-	panic("purego: struct arguments are not supported")
13	-	}
14	-
15	-	func getStruct(outType reflect.Type, syscall syscallArgs) (v reflect.Value) {
16	-	panic("purego: struct returns are not supported")
17	-	}
18	-
19	-	func placeRegisters(v reflect.Value, addFloat func(uintptr), addInt func(uintptr)) {
20	-	panic("purego: placeRegisters not implemented on 386")
21	-	}
22	-
23	-	// shouldBundleStackArgs always returns false on 386
24	-	// since C-style stack argument bundling is only needed on Darwin ARM64.
25	-	func shouldBundleStackArgs(v reflect.Value, numInts, numFloats int) bool {
26	-	return false
27	-	}
28	-
29	-	// structFitsInRegisters is not used on 386.
30	-	func structFitsInRegisters(val reflect.Value, tempNumInts, tempNumFloats int) (bool, int, int) {
31	-	panic("purego: structFitsInRegisters should not be called on 386")
32	-	}
33	-
34	-	// collectStackArgs is not used on 386.
35	-	func collectStackArgs(args []reflect.Value, startIdx int, numInts, numFloats int,
36	-	keepAlive []any, addInt, addFloat, addStack func(uintptr),
37	-	pNumInts, pNumFloats, pNumStack *int) ([]reflect.Value, []any) {
38	-	panic("purego: collectStackArgs should not be called on 386")
39	-	}
40	-
41	-	// bundleStackArgs is not used on 386.
42	-	func bundleStackArgs(stackArgs []reflect.Value, addStack func(uintptr)) {
43	-	panic("purego: bundleStackArgs should not be called on 386")
44	-	}
45	-
46	-	func getCallbackStruct(inType reflect.Type, frame unsafe.Pointer, floatsN int, intsN int, stackSlot int, stackByteOffset uintptr) reflect.Value {
47	-	panic("purego: struct callback arguments are not supported on 386")
48	-	}
49	-
50	-	func setStruct(a *callbackArgs, ret reflect.Value) {
51	-	panic("purego: struct returns are not supported on 386")
52	-	}

@@ -1,52 +0,0 @@
1	-	// SPDX-License-Identifier: Apache-2.0
2	-	// SPDX-FileCopyrightText: 2025 The Ebitengine Authors
3	-
4	-	package purego
5	-
6	-	import (
7	-	"reflect"
8	-	"unsafe"
9	-	)
10	-
11	-	func addStruct(v reflect.Value, numInts, numFloats, numStack *int, addInt, addFloat, addStack func(uintptr), keepAlive []any) []any {
12	-	panic("purego: struct arguments are not supported")
13	-	}
14	-
15	-	func getStruct(outType reflect.Type, syscall syscallArgs) (v reflect.Value) {
16	-	panic("purego: struct returns are not supported")
17	-	}
18	-
19	-	func placeRegisters(v reflect.Value, addFloat func(uintptr), addInt func(uintptr)) {
20	-	panic("purego: placeRegisters not implemented on 386")
21	-	}
22	-
23	-	// shouldBundleStackArgs always returns false on 386
24	-	// since C-style stack argument bundling is only needed on Darwin ARM64.
25	-	func shouldBundleStackArgs(v reflect.Value, numInts, numFloats int) bool {
26	-	return false
27	-	}
28	-
29	-	// structFitsInRegisters is not used on 386.
30	-	func structFitsInRegisters(val reflect.Value, tempNumInts, tempNumFloats int) (bool, int, int) {
31	-	panic("purego: structFitsInRegisters should not be called on 386")
32	-	}
33	-
34	-	// collectStackArgs is not used on 386.
35	-	func collectStackArgs(args []reflect.Value, startIdx int, numInts, numFloats int,
36	-	keepAlive []any, addInt, addFloat, addStack func(uintptr),
37	-	pNumInts, pNumFloats, pNumStack *int) ([]reflect.Value, []any) {
38	-	panic("purego: collectStackArgs should not be called on 386")
39	-	}
40	-
41	-	// bundleStackArgs is not used on 386.
42	-	func bundleStackArgs(stackArgs []reflect.Value, addStack func(uintptr)) {
43	-	panic("purego: bundleStackArgs should not be called on 386")
44	-	}
45	-
46	-	func getCallbackStruct(inType reflect.Type, frame unsafe.Pointer, floatsN int, intsN int, stackSlot int, stackByteOffset uintptr) reflect.Value {
47	-	panic("purego: struct callback arguments are not supported on 386")
48	-	}
49	-
50	-	func setStruct(a *callbackArgs, ret reflect.Value) {
51	-	panic("purego: struct returns are not supported on 386")
52	-	}

A struct_other.go +47 -0

@@ -0,0 +1,47 @@
	1	+	// SPDX-License-Identifier: Apache-2.0
	2	+	// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
	3	+
	4	+	//go:build !(amd64 \|\| arm \|\| arm64 \|\| loong64 \|\| ppc64le \|\| riscv64 \|\| s390x)
	5	+
	6	+	package purego
	7	+
	8	+	import (
	9	+	"reflect"
	10	+	"unsafe"
	11	+	)
	12	+
	13	+	// This file provides the struct-handling helpers for architectures that do
	14	+	// not support struct arguments or returns: 386, and any architecture reachable
	15	+	// only through the integer-only cgo fallback. Every struct operation panics.
	16	+
	17	+	func addStruct(v reflect.Value, numInts, numFloats, numStack *int, addInt, addFloat, addStack func(uintptr), keepAlive []any) []any {
	18	+	panic("purego: struct arguments are not supported on this architecture")
	19	+	}
	20	+
	21	+	func getStruct(outType reflect.Type, syscall syscallArgs) reflect.Value {
	22	+	panic("purego: struct returns are not supported on this architecture")
	23	+	}
	24	+
	25	+	// shouldBundleStackArgs always returns false because C-style stack argument
	26	+	// bundling is only needed on Darwin ARM64.
	27	+	func shouldBundleStackArgs(v reflect.Value, numInts, numFloats int) bool {
	28	+	return false
	29	+	}
	30	+
	31	+	func collectStackArgs(args []reflect.Value, startIdx int, numInts, numFloats int,
	32	+	keepAlive []any, addInt, addFloat, addStack func(uintptr),
	33	+	pNumInts, pNumFloats, pNumStack *int) ([]reflect.Value, []any) {
	34	+	panic("purego: collectStackArgs should not be called on this architecture")
	35	+	}
	36	+
	37	+	func bundleStackArgs(stackArgs []reflect.Value, addStack func(uintptr)) {
	38	+	panic("purego: bundleStackArgs should not be called on this architecture")
	39	+	}
	40	+
	41	+	func getCallbackStruct(inType reflect.Type, frame unsafe.Pointer, floatsN int, intsN int, stackSlot int, stackByteOffset uintptr) reflect.Value {
	42	+	panic("purego: struct callback arguments are not supported on this architecture")
	43	+	}
	44	+
	45	+	func setStruct(a *callbackArgs, ret reflect.Value) {
	46	+	panic("purego: struct returns are not supported on this architecture")
	47	+	}

@@ -0,0 +1,47 @@
	1	+	// SPDX-License-Identifier: Apache-2.0
	2	+	// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
	3	+
	4	+	//go:build !(amd64 \|\| arm \|\| arm64 \|\| loong64 \|\| ppc64le \|\| riscv64 \|\| s390x)
	5	+
	6	+	package purego
	7	+
	8	+	import (
	9	+	"reflect"
	10	+	"unsafe"
	11	+	)
	12	+
	13	+	// This file provides the struct-handling helpers for architectures that do
	14	+	// not support struct arguments or returns: 386, and any architecture reachable
	15	+	// only through the integer-only cgo fallback. Every struct operation panics.
	16	+
	17	+	func addStruct(v reflect.Value, numInts, numFloats, numStack *int, addInt, addFloat, addStack func(uintptr), keepAlive []any) []any {
	18	+	panic("purego: struct arguments are not supported on this architecture")
	19	+	}
	20	+
	21	+	func getStruct(outType reflect.Type, syscall syscallArgs) reflect.Value {
	22	+	panic("purego: struct returns are not supported on this architecture")
	23	+	}
	24	+
	25	+	// shouldBundleStackArgs always returns false because C-style stack argument
	26	+	// bundling is only needed on Darwin ARM64.
	27	+	func shouldBundleStackArgs(v reflect.Value, numInts, numFloats int) bool {
	28	+	return false
	29	+	}
	30	+
	31	+	func collectStackArgs(args []reflect.Value, startIdx int, numInts, numFloats int,
	32	+	keepAlive []any, addInt, addFloat, addStack func(uintptr),
	33	+	pNumInts, pNumFloats, pNumStack *int) ([]reflect.Value, []any) {
	34	+	panic("purego: collectStackArgs should not be called on this architecture")
	35	+	}
	36	+
	37	+	func bundleStackArgs(stackArgs []reflect.Value, addStack func(uintptr)) {
	38	+	panic("purego: bundleStackArgs should not be called on this architecture")
	39	+	}
	40	+
	41	+	func getCallbackStruct(inType reflect.Type, frame unsafe.Pointer, floatsN int, intsN int, stackSlot int, stackByteOffset uintptr) reflect.Value {
	42	+	panic("purego: struct callback arguments are not supported on this architecture")
	43	+	}
	44	+
	45	+	func setStruct(a *callbackArgs, ret reflect.Value) {
	46	+	panic("purego: struct returns are not supported on this architecture")
	47	+	}

M syscall_cgo_linux.go +4 -0


@@ -14,3 +14,7 @@ var syscallXABI0 = uintptr(cgo.SyscallXABI0)
14	14		func NewCallback(_ any) uintptr {
15	15		panic("purego: NewCallback on Linux is only supported on 386/amd64/arm64/arm/loong64/ppc64le/riscv64/s390x")
16	16		}
	17	+
	18	+	func syscall_syscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
	19	+	panic("purego: syscall_syscallN is only supported on windows")
	20	+	}


@@ -14,3 +14,7 @@ var syscallXABI0 = uintptr(cgo.SyscallXABI0)
14	func NewCallback(_ any) uintptr {	14		func NewCallback(_ any) uintptr {
15	panic("purego: NewCallback on Linux is only supported on 386/amd64/arm64/arm/loong64/ppc64le/riscv64/s390x")	15		panic("purego: NewCallback on Linux is only supported on 386/amd64/arm64/arm/loong64/ppc64le/riscv64/s390x")
16	}	16		}
		17	+
		18	+	func syscall_syscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
		19	+	panic("purego: syscall_syscallN is only supported on windows")
		20	+	}