[chore] Ability to provide custom ld and gc flags

cmd/builder/README.md

@@ -110,7 +110,20 @@ Use `ocb --help` to learn about which flags are available.
 
 ## Debug
 
-To keep the debug symbols in the resulting OpenTelemetry Collector binary, set the configuration property `debug_compilation` to true.
+### Debug symbols
+
+By default, the LDflags are set to -s -w, which strips debugging symbols to produce a smaller OpenTelemetry Collector binary. To retain debugging symbols and DWARF debugging data in the binary, override the LDflags as shown:
+
+```console 
+ocb --ldflags="" --config=builder-config.yaml.
+```
+
+### Debugging with Delve
+
+To ensure the code being executed matches the written code exactly, debugging symbols must be preserved, and compiler inlining and optimizations disabled. You can achieve this in two ways:
+
+1. Set the configuration property `debug_compilation` to true.
+2. Manually override the ldflags and gcflags `ocb --ldflags="" --gcflags="all=-N -l" --config=builder-config.yaml.`
 
 Then install `go-delve` and run OpenTelemetry Collector with `dlv` command as the following example:
 

cmd/builder/internal/builder/config.go

@@ -35,6 +35,9 @@ type Config struct {
 	SkipGetModules       bool   `mapstructure:"-"`
 	SkipStrictVersioning bool   `mapstructure:"-"`
 	LDFlags              string `mapstructure:"-"`
+	LDSet 				 bool   `mapstructure:"-"` // only used to override LDFlags
+	GCFlags              string `mapstructure:"-"`
+	GCSet				 bool   `mapstructure:"-"` // only used to override GCFlags
 	Verbose              bool   `mapstructure:"-"`
 
 	Distribution      Distribution `mapstructure:"dist"`
@@ -71,7 +74,7 @@ type Distribution struct {
 	OutputPath       string `mapstructure:"output_path"`
 	Version          string `mapstructure:"version"`
 	BuildTags        string `mapstructure:"build_tags"`
-	DebugCompilation bool   `mapstructure:"debug_compilation"`
+	DebugCompilation bool   `mapstructure:"debug_compilation"` // TODO depercate?
 }
 
 // Module represents a receiver, exporter, processor or extension for the distribution

cmd/builder/internal/builder/config_test.go

@@ -179,6 +179,10 @@ func TestNewDefaultConfig(t *testing.T) {
 	require.NoError(t, cfg.Validate())
 	assert.False(t, cfg.Distribution.DebugCompilation)
 	assert.Empty(t, cfg.Distribution.BuildTags)
+	assert.False(t, cfg.LDSet)
+	assert.Empty(t, cfg.LDFlags)
+	assert.False(t, cfg.GCSet)
+	assert.Empty(t, cfg.GCFlags)
 }
 
 func TestNewBuiltinConfig(t *testing.T) {

cmd/builder/internal/builder/main.go

@@ -109,17 +109,28 @@ func Compile(cfg *Config) error {
 
 	cfg.Logger.Info("Compiling")
 
-	ldflags := "-s -w"
+	var ldflags = "-s -w" // we strip the symbols by default for smaller binaries
+	var gcflags = ""
 
 	args := []string{"build", "-trimpath", "-o", cfg.Distribution.Name}
 	if cfg.Distribution.DebugCompilation {
 		cfg.Logger.Info("Debug compilation is enabled, the debug symbols will be left on the resulting binary")
 		ldflags = cfg.LDFlags
-		args = append(args, "-gcflags=all=-N -l")
-	} else if len(cfg.LDFlags) > 0 {
-		ldflags += " " + cfg.LDFlags
+		gcflags = "all=-N -l"
+	} else {
+		if cfg.LDSet {
+			cfg.Logger.Info("Using custom ldflags", zap.String("ldflags", cfg.LDFlags))
+			ldflags = cfg.LDFlags
+		}
+		if cfg.GCSet {
+			cfg.Logger.Info("Using custom gcflags", zap.String("gcflags", cfg.GCFlags))
+			gcflags = cfg.GCFlags
+		}
 	}
+
 	args = append(args, "-ldflags="+ldflags)
+	args = append(args, "-gcflags="+gcflags)
+
 	if cfg.Distribution.BuildTags != "" {
 		args = append(args, "-tags", cfg.Distribution.BuildTags)
 	}

cmd/builder/internal/builder/main_test.go

@@ -251,6 +251,16 @@ func TestGenerateAndCompile(t *testing.T) {
 				return cfg
 			},
 		},
+		{
+			name: "GCFlags Compilation",
+			cfgBuilder: func(t *testing.T) *Config {
+				cfg := newTestConfig(t)
+				cfg.Distribution.OutputPath = t.TempDir()
+				cfg.Replaces = append(cfg.Replaces, replaces...)
+				cfg.GCFlags = `all=-N -l`
+				return cfg
+			},
+		},
 		{
 			name: "Build Tags Compilation",
 			cfgBuilder: func(t *testing.T) *Config {

cmd/builder/internal/command.go

@@ -27,6 +27,7 @@ const (
 	skipGetModulesFlag         = "skip-get-modules"
 	skipStrictVersioningFlag   = "skip-strict-versioning"
 	ldflagsFlag                = "ldflags"
+	gcflagsFlag                = "gcflags"
 	distributionOutputPathFlag = "output-path"
 	verboseFlag                = "verbose"
 )
@@ -84,6 +85,7 @@ func initFlags(flags *flag.FlagSet) error {
 	flags.Bool(skipStrictVersioningFlag, true, "Whether builder should skip strictly checking the calculated versions following dependency resolution")
 	flags.Bool(verboseFlag, false, "Whether builder should print verbose output (default false)")
 	flags.String(ldflagsFlag, "", `ldflags to include in the "go build" command`)
+	flags.String(gcflagsFlag, "", `gcflags to include in the "go build" command`)
 	flags.String(distributionOutputPathFlag, "", "Where to write the resulting files")
 	return flags.MarkDeprecated(distributionOutputPathFlag, "use config distribution::output_path")
 }
@@ -145,8 +147,17 @@ func applyFlags(flags *flag.FlagSet, cfg *builder.Config) error {
 	cfg.SkipStrictVersioning, err = flags.GetBool(skipStrictVersioningFlag)
 	errs = multierr.Append(errs, err)
 
-	cfg.LDFlags, err = flags.GetString(ldflagsFlag)
-	errs = multierr.Append(errs, err)
+	if flags.Changed(ldflagsFlag) {
+		cfg.LDSet = true
+		cfg.LDFlags, err = flags.GetString(ldflagsFlag)
+		errs = multierr.Append(errs, err)
+	}
+	if flags.Changed(gcflagsFlag) {
+		cfg.GCSet = true
+		cfg.GCFlags, err = flags.GetString(gcflagsFlag)
+		errs = multierr.Append(errs, err)
+	}
+
 	cfg.Verbose, err = flags.GetBool(verboseFlag)
 	errs = multierr.Append(errs, err)