godebug.go

Documentation: cmd/go/internal/load

     1  // Copyright 2023 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 load
     6  
     7  import (
     8  	"cmd/go/internal/modload"
     9  	"errors"
    10  	"fmt"
    11  	"go/build"
    12  	"internal/godebugs"
    13  	"sort"
    14  	"strconv"
    15  	"strings"
    16  )
    17  
    18  var ErrNotGoDebug = errors.New("not //go:debug line")
    19  
    20  func ParseGoDebug(text string) (key, value string, err error) {
    21  	if !strings.HasPrefix(text, "//go:debug") {
    22  		return "", "", ErrNotGoDebug
    23  	}
    24  	i := strings.IndexAny(text, " \t")
    25  	if i < 0 {
    26  		if strings.TrimSpace(text) == "//go:debug" {
    27  			return "", "", fmt.Errorf("missing key=value")
    28  		}
    29  		return "", "", ErrNotGoDebug
    30  	}
    31  	k, v, ok := strings.Cut(strings.TrimSpace(text[i:]), "=")
    32  	if !ok {
    33  		return "", "", fmt.Errorf("missing key=value")
    34  	}
    35  	if strings.ContainsAny(k, " \t") {
    36  		return "", "", fmt.Errorf("key contains space")
    37  	}
    38  	if strings.ContainsAny(v, " \t") {
    39  		return "", "", fmt.Errorf("value contains space")
    40  	}
    41  	if strings.ContainsAny(k, ",") {
    42  		return "", "", fmt.Errorf("key contains comma")
    43  	}
    44  	if strings.ContainsAny(v, ",") {
    45  		return "", "", fmt.Errorf("value contains comma")
    46  	}
    47  
    48  	for _, info := range godebugs.All {
    49  		if k == info.Name {
    50  			return k, v, nil
    51  		}
    52  	}
    53  	return "", "", fmt.Errorf("unknown //go:debug setting %q", k)
    54  }
    55  
    56  // defaultGODEBUG returns the default GODEBUG setting for the main package p.
    57  // When building a test binary, directives, testDirectives, and xtestDirectives
    58  // list additional directives from the package under test.
    59  func defaultGODEBUG(p *Package, directives, testDirectives, xtestDirectives []build.Directive) string {
    60  	if p.Name != "main" {
    61  		return ""
    62  	}
    63  	goVersion := modload.MainModules.GoVersion()
    64  	if modload.RootMode == modload.NoRoot && p.Module != nil {
    65  		// This is go install pkg@version or go run pkg@version.
    66  		// Use the Go version from the package.
    67  		// If there isn't one, then
    68  		goVersion = p.Module.GoVersion
    69  		if goVersion == "" {
    70  			goVersion = "1.20"
    71  		}
    72  	}
    73  
    74  	m := godebugForGoVersion(goVersion)
    75  	for _, list := range [][]build.Directive{p.Internal.Build.Directives, directives, testDirectives, xtestDirectives} {
    76  		for _, d := range list {
    77  			k, v, err := ParseGoDebug(d.Text)
    78  			if err != nil {
    79  				continue
    80  			}
    81  			if m == nil {
    82  				m = make(map[string]string)
    83  			}
    84  			m[k] = v
    85  		}
    86  	}
    87  	var keys []string
    88  	for k := range m {
    89  		keys = append(keys, k)
    90  	}
    91  	sort.Strings(keys)
    92  	var b strings.Builder
    93  	for _, k := range keys {
    94  		if b.Len() > 0 {
    95  			b.WriteString(",")
    96  		}
    97  		b.WriteString(k)
    98  		b.WriteString("=")
    99  		b.WriteString(m[k])
   100  	}
   101  	return b.String()
   102  }
   103  
   104  func godebugForGoVersion(v string) map[string]string {
   105  	if strings.Count(v, ".") >= 2 {
   106  		i := strings.Index(v, ".")
   107  		j := i + 1 + strings.Index(v[i+1:], ".")
   108  		v = v[:j]
   109  	}
   110  
   111  	if !strings.HasPrefix(v, "1.") {
   112  		return nil
   113  	}
   114  	n, err := strconv.Atoi(v[len("1."):])
   115  	if err != nil {
   116  		return nil
   117  	}
   118  
   119  	def := make(map[string]string)
   120  	for _, info := range godebugs.All {
   121  		if n < info.Changed {
   122  			def[info.Name] = info.Old
   123  		}
   124  	}
   125  	return def
   126  }
   127
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