pkg/ifuzz: fix generate/build

Currently the commands we have in go:generate first create an empty file
and then write final contents. This breaks any parallel builds of the source.
Even running go generate ./... does not work.
Write output files atomically.

2 files changed, 11 insertions, 5 deletions

diff --git a/pkg/ifuzz/x86/gen/gen.go b/pkg/ifuzz/x86/gen/gen.go
index dc77ea497..c1af7a44e 100644
--- a/pkg/ifuzz/x86/gen/gen.go
+++ b/pkg/ifuzz/x86/gen/gen.go
@@ -7,6 +7,7 @@ package main
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"fmt"
 	"os"
@@ -16,14 +17,15 @@ import (
 
 	"github.com/google/syzkaller/pkg/ifuzz/iset"
 	"github.com/google/syzkaller/pkg/ifuzz/x86"
+	"github.com/google/syzkaller/pkg/osutil"
 	"github.com/google/syzkaller/pkg/serializer"
 	"github.com/google/syzkaller/pkg/tool"
 )
 
 // nolint: gocyclo, gocognit, funlen, dupl
 func main() {
-	if len(os.Args) != 2 {
-		tool.Failf("usage: gen instructions.txt")
+	if len(os.Args) != 3 {
+		tool.Failf("usage: gen instructions.txt output.file")
 	}
 	f, err := os.Open(os.Args[1])
 	if err != nil {
@@ -168,7 +170,8 @@ nextInsn:
 	fmt.Fprintf(os.Stderr, "deduped %v instructions\n", len(insns)-len(deduped))
 	insns = deduped
 
-	fmt.Printf(`
+	out := new(bytes.Buffer)
+	fmt.Fprintf(out, `
 // Code generated by pkg/ifuzz/x86/gen. DO NOT EDIT.
 
 //go:build !codeanalysis
@@ -183,7 +186,10 @@ func init() {
 
 var insns =
 `)
-	serializer.Write(os.Stdout, insns)
+	serializer.Write(out, insns)
+	if err := osutil.WriteFileAtomically(os.Args[2], out.Bytes()); err != nil {
+		tool.Fail(err)
+	}
 
 	fmt.Fprintf(os.Stderr, "handled %v, skipped %v\n", len(insns), skipped)
 }
diff --git a/pkg/ifuzz/x86/x86.go b/pkg/ifuzz/x86/x86.go
index a2825b9e5..053497176 100644
--- a/pkg/ifuzz/x86/x86.go
+++ b/pkg/ifuzz/x86/x86.go
@@ -1,7 +1,7 @@
 // Copyright 2017 syzkaller project authors. All rights reserved.
 // Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
 
-//go:generate bash -c "go run gen/gen.go gen/all-enc-instructions.txt > generated/insns.go"
+//go:generate go run gen/gen.go gen/all-enc-instructions.txt generated/insns.go
 
 // Package x86 allows to generate and mutate x86 machine code.
 package x86