From 7e1d19d57318d40ec13f270641b1a42f09345013 Mon Sep 17 00:00:00 2001
From: xushiwei <x@goplus.org>
Date: Sun, 4 Oct 2026 14:56:36 +0800
Subject: [PATCH] TestLongDouble

---
 c/c_test.go                                  | 31 +++++++++++++++++
 c/{ldobule_float64.go => ldouble_float64.go} |  2 +-
 c/ldouble_x87.go                             | 35 ++++++++++++++++++++
 3 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 c/c_test.go
 rename c/{ldobule_float64.go => ldouble_float64.go} (95%)
 create mode 100644 c/ldouble_x87.go

diff --git a/c/c_test.go b/c/c_test.go
new file mode 100644
index 0000000..9840805
--- /dev/null
+++ b/c/c_test.go
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2026 The XGo Authors (xgo.dev). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package c_test
+
+import (
+	"testing"
+	"unsafe"
+
+	"github.com/goplus/lib/c"
+)
+
+func TestLongDouble(t *testing.T) {
+	var ld c.LongDouble
+	if c.LongDoubleSize != unsafe.Sizeof(ld) {
+		t.Fatalf("unexpected LongDoubleSize: %d", c.LongDoubleSize)
+	}
+}
diff --git a/c/ldobule_float64.go b/c/ldouble_float64.go
similarity index 95%
rename from c/ldobule_float64.go
rename to c/ldouble_float64.go
index 903fe47..a62cbb1 100644
--- a/c/ldobule_float64.go
+++ b/c/ldouble_float64.go
@@ -1,7 +1,7 @@
 //go:build (windows && !(mingw && (amd64 || 386))) || (darwin && arm64) || arm || mips || mipsle || ((ppc64 || ppc64le) && !linux)
 
 /*
- * Copyright (c) 2024 The XGo Authors (xgo.dev). All rights reserved.
+ * Copyright (c) 2026 The XGo Authors (xgo.dev). All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/c/ldouble_x87.go b/c/ldouble_x87.go
new file mode 100644
index 0000000..c66d449
--- /dev/null
+++ b/c/ldouble_x87.go
@@ -0,0 +1,35 @@
+//go:build amd64 && (!windows || mingw)
+
+/*
+ * Copyright (c) 2026 The XGo Authors (xgo.dev). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package c
+
+// LongDouble is the x87 80-bit extended precision format, stored in 16 bytes
+// (10 significant bytes + 6 bytes padding). Applies to x86-64 on
+// Linux/macOS/BSD and MinGW on Windows.
+//
+// The C ABI requires 16-byte alignment, which Go cannot express (Go caps
+// alignment at 8); the zero-size field below gives 8-byte alignment at most.
+// When embedding LongDouble in a mirrored C struct, add explicit padding so
+// the field offset is a multiple of 16.
+type LongDouble struct {
+	_    [0]uint64
+	Data [16]byte
+}
+
+// LongDoubleSize is sizeof(long double) in bytes on this target.
+const LongDoubleSize = 16