[dev.typeparams] all: merge master (8212707) into dev.typeparams

Conflicts:

- src/go/internal/gcimporter/iimport.go

  CL 325429 and CL 319931 made unrelated changes to adjacent lines

Merge List:

+ 2021-06-07 8212707871 crypto/elliptic: update P-521 docs to say it's constant-time
+ 2021-06-07 7406180012 fmt: split package documentation into more sections
+ 2021-06-07 e3176bbc3e crypto/tls: fix typo in Config.NextProtos docs
+ 2021-06-05 e1fa26026d spec: improve wording consistency by eliminating "specifier"
+ 2021-06-05 f490134126 spec: improve wording by choosing an official term "keyword"
+ 2021-06-05 e3cb381704 go/internal/gcimporter: don't waste CPU copying bytes in `io.ReadAll`
+ 2021-06-05 9d669ed47a misc/cgo/errors: use expected column numbers
+ 2021-06-04 95939e8de7 cmd/compile/internal/abi: fix typo in comment
+ 2021-06-04 831f9376d8 net/http: fix ResponseWriter.ReadFrom with short reads
+ 2021-06-04 3a9d906edc os: avoid finalizer race in windows process object
+ 2021-06-04 105c5b50e0 os: terminate windows processes via handle directly
+ 2021-06-04 79cd407f88 syscall: regenerate zsyscall_windows.go
+ 2021-06-04 c6b6211229 doc/go1.17: document testing changes for Go 1.17
+ 2021-06-04 0214440075 syscall: do not pass console handles to PROC_THREAD_ATTRIBUTE_HANDLE_LIST on Windows 7
+ 2021-06-04 962d5c997a cmd/compile,go/types: restrict use of unsafe.{Add,Slice} to go1.17 or newer
+ 2021-06-04 b29b123e07 cmd/compile: remove spurious ir.Dump
+ 2021-06-03 6d98301114 cmd/link: use correct alignment in PE DWARF sections
+ 2021-06-03 e0d029f758 runtime: avoid gp.lockedm race in exitsyscall0
+ 2021-06-02 dd7ba3ba2c net: don't rely on system hosts in TestCVE202133195
+ 2021-06-02 4f572d7076 io/fs: minor corrections to Sub docs
+ 2021-06-02 e11d14225c doc/go1.17: remove runtime section
+ 2021-06-02 6e189afd3e doc/go1.17: mention SYS_WAIT6/WEXITED on NetBSD
+ 2021-06-02 ff9f5fb859 cmd/link: recognize clang linker error in testCGOLTO
+ 2021-06-02 1c6a2ea2ea doc/go1.17: document time changes for Go1.17
+ 2021-06-02 d743e67e06 doc/go1.17: document flag changes for Go 1.17
+ 2021-06-02 dc8f87b749 runtime/internal/sys: generate //go:build lines in gengoos.go
+ 2021-06-02 84c0e5d47f cmd/link: move issue 43830 tests out of TestScript
+ 2021-06-02 cae68700cc runtime: fix formatting
+ 2021-06-01 567ee865f6 cmd/go: add declaration to cgo_lto_issue43830 test
+ 2021-06-01 24e9707cbf cmd/link, cmd/cgo: support -flto in CFLAGS

Change-Id: I9ef88e7de0f8b1841ed9604b613b41672df67e71

12 files changed, 233 insertions, 20 deletions

diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index ae61725bc7..a73e998877 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -1638,6 +1638,8 @@ func (p *Package) gccCmd() []string {
 		c = append(c, "-maix64")
 		c = append(c, "-mcmodel=large")
 	}
+	// disable LTO so we get an object whose symbols we can read
+	c = append(c, "-fno-lto")
 	c = append(c, "-") //read input from standard input
 	return c
 }
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 8c31d5b794..94152f4278 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -168,8 +168,18 @@ func (p *Package) writeDefs() {
 			if *gccgo {
 				fmt.Fprintf(fc, "extern byte *%s;\n", n.C)
 			} else {
-				fmt.Fprintf(fm, "extern char %s[];\n", n.C)
-				fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C)
+				// Force a reference to all symbols so that
+				// the external linker will add DT_NEEDED
+				// entries as needed on ELF systems.
+				// Treat function variables differently
+				// to avoid type confict errors from LTO
+				// (Link Time Optimization).
+				if n.Kind == "fpvar" {
+					fmt.Fprintf(fm, "extern void %s();\n", n.C)
+				} else {
+					fmt.Fprintf(fm, "extern char %s[];\n", n.C)
+					fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C)
+				}
 				fmt.Fprintf(fgo2, "//go:linkname __cgo_%s %s\n", n.C, n.C)
 				fmt.Fprintf(fgo2, "//go:cgo_import_static %s\n", n.C)
 				fmt.Fprintf(fgo2, "var __cgo_%s byte\n", n.C)
@@ -1042,7 +1052,7 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 		// This unpacks the argument struct above and calls the Go function.
 		fmt.Fprintf(fgo2, "func _cgoexp%s_%s(a *%s) {\n", cPrefix, exp.ExpName, gotype)
 
-		fmt.Fprintf(fm, "int _cgoexp%s_%s;\n", cPrefix, exp.ExpName)
+		fmt.Fprintf(fm, "void _cgoexp%s_%s(void* p){}\n", cPrefix, exp.ExpName)
 
 		if gccResult != "void" {
 			// Write results back to frame.
diff --git a/src/cmd/compile/internal/abi/abiutils.go b/src/cmd/compile/internal/abi/abiutils.go
index cb8e9d7b0f..b8ea1955d1 100644
--- a/src/cmd/compile/internal/abi/abiutils.go
+++ b/src/cmd/compile/internal/abi/abiutils.go
@@ -449,7 +449,7 @@ func (config *ABIConfig) ABIAnalyze(t *types.Type, setNname bool) *ABIParamResul
 // parameterUpdateMu protects the Offset field of function/method parameters (a subset of structure Fields)
 var parameterUpdateMu sync.Mutex
 
-// FieldOffsetOf returns a concurency-safe version of f.Offset
+// FieldOffsetOf returns a concurrency-safe version of f.Offset
 func FieldOffsetOf(f *types.Field) int64 {
 	parameterUpdateMu.Lock()
 	defer parameterUpdateMu.Unlock()
diff --git a/src/cmd/compile/internal/noder/noder.go b/src/cmd/compile/internal/noder/noder.go
index 2fb852b184..08c05a69be 100644
--- a/src/cmd/compile/internal/noder/noder.go
+++ b/src/cmd/compile/internal/noder/noder.go
@@ -886,9 +886,6 @@ func (p *noder) typeExpr(typ syntax.Expr) ir.Ntype {
 	if n == nil {
 		return nil
 	}
-	if _, ok := n.(ir.Ntype); !ok {
-		ir.Dump("NOT NTYPE", n)
-	}
 	return n.(ir.Ntype)
 }
 
diff --git a/src/cmd/compile/internal/typecheck/func.go b/src/cmd/compile/internal/typecheck/func.go
index f9ee686f9e..15756a47e4 100644
--- a/src/cmd/compile/internal/typecheck/func.go
+++ b/src/cmd/compile/internal/typecheck/func.go
@@ -999,6 +999,12 @@ func tcRecover(n *ir.CallExpr) ir.Node {
 
 // tcUnsafeAdd typechecks an OUNSAFEADD node.
 func tcUnsafeAdd(n *ir.BinaryExpr) *ir.BinaryExpr {
+	if !types.AllowsGoVersion(curpkg(), 1, 17) {
+		base.ErrorfVers("go1.17", "unsafe.Add")
+		n.SetType(nil)
+		return n
+	}
+
 	n.X = AssignConv(Expr(n.X), types.Types[types.TUNSAFEPTR], "argument to unsafe.Add")
 	n.Y = DefaultLit(Expr(n.Y), types.Types[types.TINT])
 	if n.X.Type() == nil || n.Y.Type() == nil {
@@ -1015,6 +1021,12 @@ func tcUnsafeAdd(n *ir.BinaryExpr) *ir.BinaryExpr {
 
 // tcUnsafeSlice typechecks an OUNSAFESLICE node.
 func tcUnsafeSlice(n *ir.BinaryExpr) *ir.BinaryExpr {
+	if !types.AllowsGoVersion(curpkg(), 1, 17) {
+		base.ErrorfVers("go1.17", "unsafe.Slice")
+		n.SetType(nil)
+		return n
+	}
+
 	n.X = Expr(n.X)
 	n.Y = Expr(n.Y)
 	if n.X.Type() == nil || n.Y.Type() == nil {
diff --git a/src/cmd/compile/internal/types2/builtins.go b/src/cmd/compile/internal/types2/builtins.go
index 8e13b0ff18..8f2d849ef5 100644
--- a/src/cmd/compile/internal/types2/builtins.go
+++ b/src/cmd/compile/internal/types2/builtins.go
@@ -579,6 +579,11 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 
 	case _Add:
 		// unsafe.Add(ptr unsafe.Pointer, len IntegerType) unsafe.Pointer
+		if !check.allowVersion(check.pkg, 1, 17) {
+			check.error(call.Fun, "unsafe.Add requires go1.17 or later")
+			return
+		}
+
 		check.assignment(x, Typ[UnsafePointer], "argument to unsafe.Add")
 		if x.mode == invalid {
 			return
@@ -675,6 +680,11 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 
 	case _Slice:
 		// unsafe.Slice(ptr *T, len IntegerType) []T
+		if !check.allowVersion(check.pkg, 1, 17) {
+			check.error(call.Fun, "unsafe.Slice requires go1.17 or later")
+			return
+		}
+
 		typ := asPointer(x.typ)
 		if typ == nil {
 			check.errorf(x, invalidArg+"%s is not a pointer", x)
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index 50bf80ba59..bc49c6d804 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -722,14 +722,29 @@ func (t *tester) registerTests() {
 				},
 			})
 			if t.hasCxx() {
-				t.tests = append(t.tests, distTest{
-					name:    "swig_callback",
-					heading: "../misc/swig/callback",
-					fn: func(dt *distTest) error {
-						t.addCmd(dt, "misc/swig/callback", t.goTest())
-						return nil
+				t.tests = append(t.tests,
+					distTest{
+						name:    "swig_callback",
+						heading: "../misc/swig/callback",
+						fn: func(dt *distTest) error {
+							t.addCmd(dt, "misc/swig/callback", t.goTest())
+							return nil
+						},
+					},
+					distTest{
+						name:    "swig_callback_lto",
+						heading: "../misc/swig/callback",
+						fn: func(dt *distTest) error {
+							cmd := t.addCmd(dt, "misc/swig/callback", t.goTest())
+							cmd.Env = append(os.Environ(),
+								"CGO_CFLAGS=-flto",
+								"CGO_CXXFLAGS=-flto",
+								"CGO_LDFLAGS=-flto",
+							)
+							return nil
+						},
 					},
-				})
+				)
 			}
 		}
 	}
diff --git a/src/cmd/link/cgo_test.go b/src/cmd/link/cgo_test.go
new file mode 100644
index 0000000000..26ab802454
--- /dev/null
+++ b/src/cmd/link/cgo_test.go
@@ -0,0 +1,141 @@
+// Copyright 2021 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.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"internal/testenv"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+// Issues 43830, 46295
+func TestCGOLTO(t *testing.T) {
+	testenv.MustHaveCGO(t)
+	testenv.MustHaveGoBuild(t)
+
+	t.Parallel()
+
+	for _, cc := range []string{"gcc", "clang"} {
+		for test := 0; test < 2; test++ {
+			t.Run(fmt.Sprintf("%s-%d", cc, test), func(t *testing.T) {
+				testCGOLTO(t, cc, test)
+			})
+		}
+	}
+}
+
+const test1_main = `
+package main
+
+/*
+extern int myadd(int, int);
+int c_add(int a, int b) {
+	return myadd(a, b);
+}
+*/
+import "C"
+
+func main() {
+	println(C.c_add(1, 2))
+}
+`
+
+const test1_add = `
+package main
+
+import "C"
+
+/* test */
+
+//export myadd
+func myadd(a C.int, b C.int) C.int {
+	return a + b
+}
+`
+
+const test2_main = `
+package main
+
+import "fmt"
+
+/*
+#include <stdio.h>
+
+void hello(void) {
+  printf("hello\n");
+}
+*/
+import "C"
+
+func main() {
+	hello := C.hello
+	fmt.Printf("%v\n", hello)
+}
+`
+
+func testCGOLTO(t *testing.T, cc string, test int) {
+	t.Parallel()
+
+	if _, err := exec.LookPath(cc); err != nil {
+		t.Skipf("no %s compiler", cc)
+	}
+
+	dir := t.TempDir()
+
+	writeTempFile := func(name, contents string) {
+		if err := os.WriteFile(filepath.Join(dir, name), []byte(contents), 0644); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	writeTempFile("go.mod", "module cgolto\n")
+
+	switch test {
+	case 0:
+		writeTempFile("main.go", test1_main)
+		writeTempFile("add.go", test1_add)
+	case 1:
+		writeTempFile("main.go", test2_main)
+	default:
+		t.Fatalf("bad case %d", test)
+	}
+
+	cmd := exec.Command(testenv.GoToolPath(t), "build")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(),
+		"CC="+cc,
+		"CGO_CFLAGS=-flto",
+	)
+
+	t.Log("go build")
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+
+	if err != nil {
+		t.Logf("go build failed: %v", err)
+
+		// Error messages we've seen indicating that LTO is not supported.
+		// These errors come from GCC or clang, not Go.
+		var noLTO = []string{
+			`unrecognized command line option "-flto"`,
+			"unable to pass LLVM bit-code files to linker",
+			"file not recognized: File format not recognized",
+			"LTO support has not been enabled",
+			"linker command failed with exit code",
+			"gcc: can't load library",
+		}
+		for _, msg := range noLTO {
+			if bytes.Contains(out, []byte(msg)) {
+				t.Skipf("C compiler %v does not support LTO", cc)
+			}
+		}
+
+		t.Error("failed")
+	}
+}
diff --git a/src/cmd/link/internal/ld/ar.go b/src/cmd/link/internal/ld/ar.go
index 22f53a4df2..23915f9032 100644
--- a/src/cmd/link/internal/ld/ar.go
+++ b/src/cmd/link/internal/ld/ar.go
@@ -124,6 +124,10 @@ func hostArchive(ctxt *Link, name string) {
 
 			libgcc := sym.Library{Pkg: "libgcc"}
 			h := ldobj(ctxt, f, &libgcc, l, pname, name)
+			if h.ld == nil {
+				Errorf(nil, "%s unrecognized object file at offset %d", name, off)
+				continue
+			}
 			f.MustSeek(h.off, 0)
 			h.ld(ctxt, f, h.pkg, h.length, h.pn)
 		}
diff --git a/src/cmd/link/internal/ld/config.go b/src/cmd/link/internal/ld/config.go
index ae0d7520eb..20f1d0b8c1 100644
--- a/src/cmd/link/internal/ld/config.go
+++ b/src/cmd/link/internal/ld/config.go
@@ -241,6 +241,10 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 		return true, "dynamically linking with a shared library"
 	}
 
+	if unknownObjFormat {
+		return true, "some input objects have an unrecognized file format"
+	}
+
 	return false, ""
 }
 
@@ -248,7 +252,7 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 //
 // It is called after flags are processed and inputs are processed,
 // so the ctxt.LinkMode variable has an initial value from the -linkmode
-// flag and the iscgo externalobj variables are set.
+// flag and the iscgo, externalobj, and unknownObjFormat variables are set.
 func determineLinkMode(ctxt *Link) {
 	extNeeded, extReason := mustLinkExternal(ctxt)
 	via := ""
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index e8f001ba8e..644faeb2fb 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -343,10 +343,16 @@ var (
 const pkgdef = "__.PKGDEF"
 
 var (
-	// Set if we see an object compiled by the host compiler that is not
-	// from a package that is known to support internal linking mode.
+	// externalobj is set to true if we see an object compiled by
+	// the host compiler that is not from a package that is known
+	// to support internal linking mode.
 	externalobj = false
-	theline     string
+
+	// unknownObjFormat is set to true if we see an object whose
+	// format we don't recognize.
+	unknownObjFormat = false
+
+	theline string
 )
 
 func Lflag(ctxt *Link, arg string) {
@@ -1065,6 +1071,10 @@ func hostobjs(ctxt *Link) {
 		}
 
 		f.MustSeek(h.off, 0)
+		if h.ld == nil {
+			Errorf(nil, "%s: unrecognized object file format", h.pn)
+			continue
+		}
 		h.ld(ctxt, f, h.pkg, h.length, h.pn)
 		f.Close()
 	}
@@ -1855,6 +1865,14 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 		return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
 	}
 
+	if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
+		// An unrecognized object is just passed to the external linker.
+		// If we try to read symbols from this object, we will
+		// report an error at that time.
+		unknownObjFormat = true
+		return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
+	}
+
 	/* check the header */
 	line, err := f.ReadString('\n')
 	if err != nil {
@@ -1874,7 +1892,7 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 			return nil
 		}
 
-		Errorf(nil, "%s: not an object file: @%d %02x%02x%02x%02x", pn, start, c1, c2, c3, c4)
+		Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
 		return nil
 	}
 
diff --git a/src/cmd/link/internal/ld/pe.go b/src/cmd/link/internal/ld/pe.go
index 3540c07da1..8eb4231c3a 100644
--- a/src/cmd/link/internal/ld/pe.go
+++ b/src/cmd/link/internal/ld/pe.go
@@ -475,7 +475,7 @@ func (f *peFile) addDWARFSection(name string, size int) *peSection {
 	off := f.stringTable.add(name)
 	h := f.addSection(name, size, size)
 	h.shortName = fmt.Sprintf("/%d", off)
-	h.characteristics = IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_DISCARDABLE | IMAGE_SCN_CNT_INITIALIZED_DATA
+	h.characteristics = IMAGE_SCN_ALIGN_1BYTES | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_DISCARDABLE | IMAGE_SCN_CNT_INITIALIZED_DATA
 	return h
 }