godebug.go

     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  	"errors"
     9  	"fmt"
    10  	"go/build"
    11  	"internal/godebugs"
    12  	"maps"
    13  	"sort"
    14  	"strconv"
    15  	"strings"
    16  
    17  	"cmd/go/internal/fips140"
    18  	"cmd/go/internal/gover"
    19  	"cmd/go/internal/modload"
    20  )
    21  
    22  var ErrNotGoDebug = errors.New("not //go:debug line")
    23  
    24  func ParseGoDebug(text string) (key, value string, err error) {
    25  	if !strings.HasPrefix(text, "//go:debug") {
    26  		return "", "", ErrNotGoDebug
    27  	}
    28  	i := strings.IndexAny(text, " \t")
    29  	if i < 0 {
    30  		if strings.TrimSpace(text) == "//go:debug" {
    31  			return "", "", fmt.Errorf("missing key=value")
    32  		}
    33  		return "", "", ErrNotGoDebug
    34  	}
    35  	k, v, ok := strings.Cut(strings.TrimSpace(text[i:]), "=")
    36  	if !ok {
    37  		return "", "", fmt.Errorf("missing key=value")
    38  	}
    39  	if err := modload.CheckGodebug("//go:debug setting", k, v); err != nil {
    40  		return "", "", err
    41  	}
    42  	return k, v, nil
    43  }
    44  
    45  // defaultGODEBUG returns the default GODEBUG setting for the main package p.
    46  // When building a test binary, directives, testDirectives, and xtestDirectives
    47  // list additional directives from the package under test.
    48  func defaultGODEBUG(p *Package, directives, testDirectives, xtestDirectives []build.Directive) string {
    49  	if p.Name != "main" {
    50  		return ""
    51  	}
    52  	goVersion := modload.MainModules.GoVersion()
    53  	if modload.RootMode == modload.NoRoot && p.Module != nil {
    54  		// This is go install pkg@version or go run pkg@version.
    55  		// Use the Go version from the package.
    56  		// If there isn't one, then assume Go 1.20,
    57  		// the last version before GODEBUGs were introduced.
    58  		goVersion = p.Module.GoVersion
    59  		if goVersion == "" {
    60  			goVersion = "1.20"
    61  		}
    62  	}
    63  
    64  	var m map[string]string
    65  
    66  	// If GOFIPS140 is set to anything but "off",
    67  	// default to GODEBUG=fips140=on.
    68  	if fips140.Enabled() {
    69  		if m == nil {
    70  			m = make(map[string]string)
    71  		}
    72  		m["fips140"] = "on"
    73  	}
    74  
    75  	// Add directives from main module go.mod.
    76  	for _, g := range modload.MainModules.Godebugs() {
    77  		if m == nil {
    78  			m = make(map[string]string)
    79  		}
    80  		m[g.Key] = g.Value
    81  	}
    82  
    83  	// Add directives from packages.
    84  	for _, list := range [][]build.Directive{p.Internal.Build.Directives, directives, testDirectives, xtestDirectives} {
    85  		for _, d := range list {
    86  			k, v, err := ParseGoDebug(d.Text)
    87  			if err != nil {
    88  				continue
    89  			}
    90  			if m == nil {
    91  				m = make(map[string]string)
    92  			}
    93  			m[k] = v
    94  		}
    95  	}
    96  	if v, ok := m["default"]; ok {
    97  		delete(m, "default")
    98  		v = strings.TrimPrefix(v, "go")
    99  		if gover.IsValid(v) {
   100  			goVersion = v
   101  		}
   102  	}
   103  
   104  	defaults := godebugForGoVersion(goVersion)
   105  	if defaults != nil {
   106  		// Apply m on top of defaults.
   107  		maps.Copy(defaults, m)
   108  		m = defaults
   109  	}
   110  
   111  	keys := make([]string, 0, len(m))
   112  	for k := range m {
   113  		keys = append(keys, k)
   114  	}
   115  	sort.Strings(keys)
   116  	var b strings.Builder
   117  	for _, k := range keys {
   118  		if b.Len() > 0 {
   119  			b.WriteString(",")
   120  		}
   121  		b.WriteString(k)
   122  		b.WriteString("=")
   123  		b.WriteString(m[k])
   124  	}
   125  	return b.String()
   126  }
   127  
   128  func godebugForGoVersion(v string) map[string]string {
   129  	if strings.Count(v, ".") >= 2 {
   130  		i := strings.Index(v, ".")
   131  		j := i + 1 + strings.Index(v[i+1:], ".")
   132  		v = v[:j]
   133  	}
   134  
   135  	if !strings.HasPrefix(v, "1.") {
   136  		return nil
   137  	}
   138  	n, err := strconv.Atoi(v[len("1."):])
   139  	if err != nil {
   140  		return nil
   141  	}
   142  
   143  	def := make(map[string]string)
   144  	for _, info := range godebugs.All {
   145  		if n < info.Changed {
   146  			def[info.Name] = info.Old
   147  		}
   148  	}
   149  	return def
   150  }
   151
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