From 73044738e146bec259f7b8e89ecc816a421921aa Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Wed, 28 May 2014 19:50:19 -0400 Subject: cmd/gc: fix x=x crash The 'nodarg' function is used to obtain a Node* representing a function argument or result. It returned a brand new Node*, but that violates the guarantee in most places in the compiler that two Node*s refer to the same variable if and only if they are the same Node* pointer. Reestablish that invariant by making nodarg return a preexisting named variable if present. Having fixed that, avoid any copy during x=x in componentgen, because the VARDEF we emit before the copy marks the lhs x as dead incorrectly. The change in walk.c avoids modifying the result of nodarg. This was the only place in the compiler that did so. Fixes issue 8097. LGTM=r, khr R=golang-codereviews, r, khr CC=golang-codereviews, iant https://codereview.appspot.com/102820043 --- test/live.go | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'test/live.go') diff --git a/test/live.go b/test/live.go index 21d3e6a5f..286fcc306 100644 --- a/test/live.go +++ b/test/live.go @@ -564,3 +564,29 @@ func f38(b bool) { } println() } + +// issue 8097: mishandling of x = x during return. + +func f39() (x []int) { + x = []int{1} + println() // ERROR "live at call to printnl: x" + return x +} + +func f39a() (x []int) { + x = []int{1} + println() // ERROR "live at call to printnl: x" + return +} + +func f39b() (x [10]*int) { + x = [10]*int{new(int)} // ERROR "live at call to new: x" + println() // ERROR "live at call to printnl: x" + return x +} + +func f39c() (x [10]*int) { + x = [10]*int{new(int)} // ERROR "live at call to new: x" + println() // ERROR "live at call to printnl: x" + return +} -- cgit v1.2.1