link_test.go

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package big
     6  
     7  import (
     8  	"bytes"
     9  	"internal/testenv"
    10  	"os"
    11  	"os/exec"
    12  	"path/filepath"
    13  	"testing"
    14  )
    15  
    16  // Tests that the linker is able to remove references to Float, Rat,
    17  // and Int if unused (notably, not used by init).
    18  func TestLinkerGC(t *testing.T) {
    19  	if testing.Short() {
    20  		t.Skip("skipping in short mode")
    21  	}
    22  	t.Parallel()
    23  	tmp := t.TempDir()
    24  	goBin := testenv.GoToolPath(t)
    25  	goFile := filepath.Join(tmp, "x.go")
    26  	file := []byte(`package main
    27  import _ "math/big"
    28  func main() {}
    29  `)
    30  	if err := os.WriteFile(goFile, file, 0644); err != nil {
    31  		t.Fatal(err)
    32  	}
    33  	cmd := exec.Command(goBin, "build", "-o", "x.exe", "x.go")
    34  	cmd.Dir = tmp
    35  	if out, err := cmd.CombinedOutput(); err != nil {
    36  		t.Fatalf("compile: %v, %s", err, out)
    37  	}
    38  
    39  	cmd = exec.Command(goBin, "tool", "nm", "x.exe")
    40  	cmd.Dir = tmp
    41  	nm, err := cmd.CombinedOutput()
    42  	if err != nil {
    43  		t.Fatalf("nm: %v, %s", err, nm)
    44  	}
    45  	const want = "runtime.main"
    46  	if !bytes.Contains(nm, []byte(want)) {
    47  		// Test the test.
    48  		t.Errorf("expected symbol %q not found", want)
    49  	}
    50  	bad := []string{
    51  		"math/big.(*Float)",
    52  		"math/big.(*Rat)",
    53  		"math/big.(*Int)",
    54  	}
    55  	for _, sym := range bad {
    56  		if bytes.Contains(nm, []byte(sym)) {
    57  			t.Errorf("unexpected symbol %q found", sym)
    58  		}
    59  	}
    60  	if t.Failed() {
    61  		t.Logf("Got: %s", nm)
    62  	}
    63  }
    64
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