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From 7a6e3f07acfd822aa1d62f1c715125e30d67d089 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Mon, 03 Nov 2025 15:54:39 -0800
Subject: [PATCH] cmd/cgo: strip top-level const qualifier from argument frame struct
Otherwise we can't assign to it.
Fixes #75751
Change-Id: Iba680db672297bca1a1d1a33912b80863da66a08
---
diff --git a/src/cmd/cgo/internal/test/test.go b/src/cmd/cgo/internal/test/test.go
index 9626407..e83e367 100644
--- a/src/cmd/cgo/internal/test/test.go
+++ b/src/cmd/cgo/internal/test/test.go
@@ -953,6 +953,12 @@
} issue69086struct;
static int issue690861(issue69086struct* p) { p->b = 1234; return p->c; }
static int issue690862(unsigned long ul1, unsigned long ul2, unsigned int u, issue69086struct s) { return (int)(s.b); }
+
+char issue75751v = 1;
+char * const issue75751p = &issue75751v;
+#define issue75751m issue75751p
+char * const volatile issue75751p2 = &issue75751v;
+#define issue75751m2 issue75751p2
*/
import "C"
@@ -2396,3 +2402,8 @@
t.Errorf("call: got %d, want 1234", got)
}
}
+
+// Issue 75751: no runtime test, just make sure it compiles.
+func test75751() int {
+ return int(*C.issue75751m) + int(*C.issue75751m2)
+}
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 394e766..05d9dcf 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -457,6 +457,33 @@
// Also assumes that gc convention is to word-align the
// input and output parameters.
func (p *Package) structType(n *Name) (string, int64) {
+ // It's possible for us to see a type with a top-level const here,
+ // which will give us an unusable struct type. See #75751.
+ // The top-level const will always appear as a final qualifier,
+ // constructed by typeConv.loadType in the dwarf.QualType case.
+ // The top-level const is meaningless here and can simply be removed.
+ stripConst := func(s string) string {
+ i := strings.LastIndex(s, "const")
+ if i == -1 {
+ return s
+ }
+
+ // A top-level const can only be followed by other qualifiers.
+ if r, ok := strings.CutSuffix(s, "const"); ok {
+ return r
+ }
+
+ for _, f := range strings.Fields(s[i:]) {
+ switch f {
+ case "const", "restrict", "volatile":
+ default:
+ return s
+ }
+ }
+
+ return strings.TrimSpace(s[:i]) + strings.TrimSpace(s[i+len("const"):])
+ }
+
var buf strings.Builder
fmt.Fprint(&buf, "struct {\n")
off := int64(0)
@@ -468,7 +495,7 @@
}
c := t.Typedef
if c == "" {
- c = t.C.String()
+ c = stripConst(t.C.String())
}
fmt.Fprintf(&buf, "\t\t%s p%d;\n", c, i)
off += t.Size
@@ -484,7 +511,7 @@
fmt.Fprintf(&buf, "\t\tchar __pad%d[%d];\n", off, pad)
off += pad
}
- fmt.Fprintf(&buf, "\t\t%s r;\n", t.C)
+ fmt.Fprintf(&buf, "\t\t%s r;\n", stripConst(t.C.String()))
off += t.Size
}
if off%p.PtrSize != 0 {
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