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Source file src/cmd/link/linkbig_test.go

Documentation: cmd/link

  // Copyright 2016 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.
  
  // This program generates a test to verify that a program can be
  // successfully linked even when there are very large text
  // sections present.
  
  package main
  
  import (
  	"bytes"
  	"cmd/internal/objabi"
  	"fmt"
  	"internal/testenv"
  	"io/ioutil"
  	"os"
  	"os/exec"
  	"testing"
  )
  
  func TestLargeText(t *testing.T) {
  	if testing.Short() || (objabi.GOARCH != "ppc64le" && objabi.GOARCH != "ppc64" && objabi.GOARCH != "arm") {
  		t.Skipf("Skipping large text section test in short mode or on %s", objabi.GOARCH)
  	}
  	testenv.MustHaveGoBuild(t)
  
  	var w bytes.Buffer
  	const FN = 4
  	tmpdir, err := ioutil.TempDir("", "bigtext")
  
  	defer os.RemoveAll(tmpdir)
  
  	// Generate the scenario where the total amount of text exceeds the
  	// limit for the jmp/call instruction, on RISC architectures like ppc64le,
  	// which is 2^26.  When that happens the call requires special trampolines or
  	// long branches inserted by the linker where supported.
  	// Multiple .s files are generated instead of one.
  	instOnArch := map[string]string{
  		"ppc64":   "\tMOVD\tR0,R3\n",
  		"ppc64le": "\tMOVD\tR0,R3\n",
  		"arm":     "\tMOVW\tR0,R1\n",
  	}
  	inst := instOnArch[objabi.GOARCH]
  	for j := 0; j < FN; j++ {
  		testname := fmt.Sprintf("bigfn%d", j)
  		fmt.Fprintf(&w, "TEXT ·%s(SB),$0\n", testname)
  		for i := 0; i < 2200000; i++ {
  			fmt.Fprintf(&w, inst)
  		}
  		fmt.Fprintf(&w, "\tRET\n")
  		err := ioutil.WriteFile(tmpdir+"/"+testname+".s", w.Bytes(), 0666)
  		if err != nil {
  			t.Fatalf("can't write output: %v\n", err)
  		}
  		w.Reset()
  	}
  	fmt.Fprintf(&w, "package main\n")
  	fmt.Fprintf(&w, "\nimport (\n")
  	fmt.Fprintf(&w, "\t\"os\"\n")
  	fmt.Fprintf(&w, "\t\"fmt\"\n")
  	fmt.Fprintf(&w, ")\n\n")
  
  	for i := 0; i < FN; i++ {
  		fmt.Fprintf(&w, "func bigfn%d()\n", i)
  	}
  	fmt.Fprintf(&w, "\nfunc main() {\n")
  
  	// There are lots of dummy code generated in the .s files just to generate a lot
  	// of text. Link them in but guard their call so their code is not executed but
  	// the main part of the program can be run.
  	fmt.Fprintf(&w, "\tif os.Getenv(\"LINKTESTARG\") != \"\" {\n")
  	for i := 0; i < FN; i++ {
  		fmt.Fprintf(&w, "\t\tbigfn%d()\n", i)
  	}
  	fmt.Fprintf(&w, "\t}\n")
  	fmt.Fprintf(&w, "\tfmt.Printf(\"PASS\\n\")\n")
  	fmt.Fprintf(&w, "}")
  	err = ioutil.WriteFile(tmpdir+"/bigfn.go", w.Bytes(), 0666)
  	if err != nil {
  		t.Fatalf("can't write output: %v\n", err)
  	}
  
  	// Build and run with internal linking.
  	os.Chdir(tmpdir)
  	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", "bigtext")
  	out, err := cmd.CombinedOutput()
  	if err != nil {
  		t.Fatalf("Build failed for big text program with internal linking: %v, output: %s", err, out)
  	}
  	cmd = exec.Command(tmpdir + "/bigtext")
  	out, err = cmd.CombinedOutput()
  	if err != nil {
  		t.Fatalf("Program built with internal linking failed to run with err %v, output: %s", err, out)
  	}
  
  	// Build and run with external linking
  	os.Chdir(tmpdir)
  	cmd = exec.Command(testenv.GoToolPath(t), "build", "-o", "bigtext", "-ldflags", "'-linkmode=external'")
  	out, err = cmd.CombinedOutput()
  	if err != nil {
  		t.Fatalf("Build failed for big text program with external linking: %v, output: %s", err, out)
  	}
  	cmd = exec.Command(tmpdir + "/bigtext")
  	out, err = cmd.CombinedOutput()
  	if err != nil {
  		t.Fatalf("Program built with external linking failed to run with err %v, output: %s", err, out)
  	}
  }
  

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