From 244c8b050093ec546311707760afaafabcbf2fef Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Wed, 20 Jul 2022 12:46:33 -0700 Subject: [PATCH] cmd/cgo: allow cgo to pass strings or []bytes bigger than 1<<30 There's no real reason to limit to 1<<30 bytes. Maybe it would catch some mistakes, but probably ones that would quickly manifest in other ways. We can't use the fancy new unsafe.Slice function because this code may still be generated for people with 1.16 or earlier in their go.mod file. Use unsafe shenanigans instead. Fixes #53965 Fixes #53958 Change-Id: Ibfa095192f50276091d6c2532e8ccd7832b57ca8 Reviewed-on: https://go-review.googlesource.com/c/go/+/418557 Run-TryBot: Keith Randall Reviewed-by: Ian Lance Taylor Reviewed-by: Keith Randall TryBot-Result: Gopher Robot --- src/cmd/cgo/out.go | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go index d6740028da..119eca2be7 100644 --- a/src/cmd/cgo/out.go +++ b/src/cmd/cgo/out.go @@ -1653,10 +1653,18 @@ const cStringDef = ` // freed, such as by calling C.free (be sure to include stdlib.h // if C.free is needed). func _Cfunc_CString(s string) *_Ctype_char { + if len(s)+1 <= 0 { + panic("string too large") + } p := _cgo_cmalloc(uint64(len(s)+1)) - pp := (*[1<<30]byte)(p) - copy(pp[:], s) - pp[len(s)] = 0 + sliceHeader := struct { + p unsafe.Pointer + len int + cap int + }{p, len(s)+1, len(s)+1} + b := *(*[]byte)(unsafe.Pointer(&sliceHeader)) + copy(b, s) + b[len(s)] = 0 return (*_Ctype_char)(p) } ` @@ -1670,8 +1678,13 @@ const cBytesDef = ` // if C.free is needed). func _Cfunc_CBytes(b []byte) unsafe.Pointer { p := _cgo_cmalloc(uint64(len(b))) - pp := (*[1<<30]byte)(p) - copy(pp[:], b) + sliceHeader := struct { + p unsafe.Pointer + len int + cap int + }{p, len(b), len(b)} + s := *(*[]byte)(unsafe.Pointer(&sliceHeader)) + copy(s, b) return p } ` -- 2.48.1