From 160914e33ca6521d74297291d801062cc44d794d Mon Sep 17 00:00:00 2001 From: Cherry Zhang Date: Mon, 6 Feb 2017 14:24:16 -0500 Subject: [PATCH] cmd/compile: do not use "oaslit" for global The compiler did not emit write barrier for assigning global with struct literal, like global = T{} where T contains pointer. The relevant code path is: walkexpr OAS var_ OSTRUCTLIT oaslit anylit OSTRUCTLIT walkexpr OAS var_ nil return without adding write barrier return true break (without adding write barrier) This CL makes oaslit not apply to globals. See also CL https://go-review.googlesource.com/c/36355/ for an alternative fix. The downside of this is that it generates static data for zeroing struct now. Also this only covers global. If there is any lurking bug with implicit zeroing other than globals, this doesn't fix. Fixes #18956. Change-Id: Ibcd27e4fae3aa38390ffa94a32a9dd7a802e4b37 Reviewed-on: https://go-review.googlesource.com/36410 Reviewed-by: Russ Cox Run-TryBot: Cherry Zhang TryBot-Result: Gobot Gobot --- src/cmd/compile/internal/gc/sinit.go | 2 +- test/writebarrier.go | 16 ++++++++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/src/cmd/compile/internal/gc/sinit.go b/src/cmd/compile/internal/gc/sinit.go index 756c31d954..19b2222861 100644 --- a/src/cmd/compile/internal/gc/sinit.go +++ b/src/cmd/compile/internal/gc/sinit.go @@ -585,7 +585,7 @@ func isliteral(n *Node) bool { } func (n *Node) isSimpleName() bool { - return n.Op == ONAME && n.Addable && n.Class != PAUTOHEAP + return n.Op == ONAME && n.Addable && n.Class != PAUTOHEAP && n.Class != PEXTERN } func litas(l *Node, r *Node, init *Nodes) { diff --git a/test/writebarrier.go b/test/writebarrier.go index 6460a6f9da..13f7b54608 100644 --- a/test/writebarrier.go +++ b/test/writebarrier.go @@ -220,3 +220,19 @@ func f22(x *int) (y *int) { *p = x // no barrier return } + +type T23 struct { + p *int + a int +} + +var t23 T23 +var i23 int + +func f23() { + // zeroing global needs write barrier for the hybrid barrier. + t23 = T23{} // ERROR "write barrier" + // also test partial assignments + t23 = T23{a: 1} // ERROR "write barrier" + t23 = T23{p: &i23} // ERROR "write barrier" +} -- 2.48.1