From 89020aa72cbdff82ab35af759246c85c26462dfe Mon Sep 17 00:00:00 2001 From: Andrew Gerrand Date: Fri, 26 Jul 2013 10:04:32 +1000 Subject: [PATCH] [release-branch.go1.1] cmd/gc: avoid passing unevaluated constant expressions to backends. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit ««« CL 11107044 / 5baf6060648e cmd/gc: avoid passing unevaluated constant expressions to backends. Backends do not exactly expect receiving binary operators with constant operands or use workarounds to move them to register/stack in order to handle them. Fixes #5841. R=golang-dev, daniel.morsing, rsc CC=golang-dev https://golang.org/cl/11107044 »»» Update #5928 R=golang-dev, dave CC=golang-dev https://golang.org/cl/11879044 --- src/cmd/gc/walk.c | 7 +++++++ test/fixedbugs/issue5841.go | 16 ++++++++++++++++ 2 files changed, 23 insertions(+) create mode 100644 test/fixedbugs/issue5841.go diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c index d9c6341b43..e8ebd28924 100644 --- a/src/cmd/gc/walk.c +++ b/src/cmd/gc/walk.c @@ -1338,6 +1338,13 @@ walkexpr(Node **np, NodeList **init) fatal("missing switch %O", n->op); ret: + // Expressions that are constant at run time but not + // considered const by the language spec are not turned into + // constants until walk. For example, if n is y%1 == 0, the + // walk of y%1 may have replaced it by 0. + // Check whether n with its updated args is itself now a constant. + evconst(n); + ullmancalc(n); if(debug['w'] && n != N) diff --git a/test/fixedbugs/issue5841.go b/test/fixedbugs/issue5841.go new file mode 100644 index 0000000000..cfc4a504c5 --- /dev/null +++ b/test/fixedbugs/issue5841.go @@ -0,0 +1,16 @@ +// build + +// Copyright 2013 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Issue 5841: 8g produces invalid CMPL $0, $0. +// Similar to issue 5002, used to fail at link time. + +package main + +func main() { + var y int + if y%1 == 0 { + } +} -- 2.50.0