From c9446398e8d72263f75c11bb835d75421627b3a3 Mon Sep 17 00:00:00 2001 From: Josh Bleecher Snyder Date: Thu, 9 Mar 2017 22:41:32 -0800 Subject: [PATCH] cmd/compile: allow composite literal structs with _ fields Given code such as type T struct { _ string } func f() { var x = T{"space"} // ... } the compiler rewrote the 'var x' line as var x T x._ = "space" The compiler then rejected the assignment to a blank field, thus rejecting valid code. It also failed to catch a number of invalid assignments. And there were insufficient checks for validity when emitting static data, leading to ICEs. To fix, check earlier for explicit blanks field names, explicitly handle legit blanks in sinit, and don't try to emit static data for nodes for which typechecking has failed. Fixes #19482 Change-Id: I594476171d15e6e8ecc6a1749e3859157fe2c929 Reviewed-on: https://go-review.googlesource.com/38006 Run-TryBot: Josh Bleecher Snyder Reviewed-by: Matthew Dempsky TryBot-Result: Gobot Gobot --- src/cmd/compile/internal/gc/sinit.go | 9 ++++++- src/cmd/compile/internal/gc/typecheck.go | 2 +- src/cmd/internal/obj/data.go | 2 +- test/fixedbugs/issue19482.go | 34 ++++++++++++++++++++++++ 4 files changed, 44 insertions(+), 3 deletions(-) create mode 100644 test/fixedbugs/issue19482.go diff --git a/src/cmd/compile/internal/gc/sinit.go b/src/cmd/compile/internal/gc/sinit.go index 47aee51c17..0ff94abe2e 100644 --- a/src/cmd/compile/internal/gc/sinit.go +++ b/src/cmd/compile/internal/gc/sinit.go @@ -725,6 +725,9 @@ func fixedlit(ctxt initContext, kind initKind, n *Node, var_ *Node, init *Nodes) if r.Op != OSTRUCTKEY { Fatalf("fixedlit: rhs not OSTRUCTKEY: %v", r) } + if isblanksym(r.Sym) { + return nblank, r.Left + } return nodSym(ODOT, var_, r.Sym), r.Left } default: @@ -1346,8 +1349,12 @@ func isvaluelit(n *Node) bool { } func genAsStatic(as *Node) { + if as.Left.Type == nil { + Fatalf("genAsStatic as.Left not typechecked") + } + var nam Node - if !stataddr(&nam, as.Left) || nam.Class != PEXTERN { + if !stataddr(&nam, as.Left) || (nam.Class != PEXTERN && as.Left != nblank) { Fatalf("genAsStatic: lhs %v", as.Left) } diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go index b272d27612..db4ea0a895 100644 --- a/src/cmd/compile/internal/gc/typecheck.go +++ b/src/cmd/compile/internal/gc/typecheck.go @@ -3100,7 +3100,7 @@ func typecheckcomplit(n *Node) *Node { // the field to the right of the dot, // so s will be non-nil, but an OXDOT // is never a valid struct literal key. - if key.Sym == nil || key.Op == OXDOT { + if key.Sym == nil || key.Op == OXDOT || isblanksym(key.Sym) { yyerror("invalid field name %v in struct initializer", key) l.Left = typecheck(l.Left, Erv) continue diff --git a/src/cmd/internal/obj/data.go b/src/cmd/internal/obj/data.go index 114841dedb..5f583071e6 100644 --- a/src/cmd/internal/obj/data.go +++ b/src/cmd/internal/obj/data.go @@ -70,7 +70,7 @@ func (s *LSym) GrowCap(c int64) { // prepwrite prepares to write data of size siz into s at offset off. func (s *LSym) prepwrite(ctxt *Link, off int64, siz int) { if off < 0 || siz < 0 || off >= 1<<30 { - log.Fatalf("prepwrite: bad off=%d siz=%d s=%v", off, siz, s) + ctxt.Diag("prepwrite: bad off=%d siz=%d s=%v", off, siz, s) } if s.Type == SBSS || s.Type == STLSBSS { ctxt.Diag("cannot supply data for BSS var") diff --git a/test/fixedbugs/issue19482.go b/test/fixedbugs/issue19482.go new file mode 100644 index 0000000000..97497a434c --- /dev/null +++ b/test/fixedbugs/issue19482.go @@ -0,0 +1,34 @@ +// errorcheck + +// Copyright 2017 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. + +// Compiler rejected initialization of structs to composite literals +// in a non-static setting (e.g. in a function) +// when the struct contained a field named _. + +package p + +type T struct { + _ string +} + +func ok() { + var x = T{"check"} + _ = x + _ = T{"et"} +} + +var ( + y = T{"stare"} + w = T{_: "look"} // ERROR "invalid field name _ in struct initializer" + _ = T{"page"} + _ = T{_: "out"} // ERROR "invalid field name _ in struct initializer" +) + +func bad() { + var z = T{_: "verse"} // ERROR "invalid field name _ in struct initializer" + _ = z + _ = T{_: "itinerary"} // ERROR "invalid field name _ in struct initializer" +} -- 2.48.1