goenv: read git hash embedded in the binary

This PR makes two practical changes:

  * The git hash is read from the binary itself instead of embedding it
    with a `-ldflags` flag. This means it is also present when building
    TinyGo using `go build` or `go install`.
  * A flag is added to indicate whether the tree was modified. This
    might aid in helping people: it is now easier to see whether they
    have made local modifications.

Author: aykevl

GNUmakefile

@@ -291,7 +291,7 @@ endif
 
 tinygo: ## Build the TinyGo compiler
 	@if [ ! -f "$(LLVM_BUILDDIR)/bin/llvm-config" ]; then echo "Fetch and build LLVM first by running:"; echo "  $(MAKE) llvm-source"; echo "  $(MAKE) $(LLVM_BUILDDIR)"; exit 1; fi
-	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GOENVFLAGS) $(GO) build -buildmode exe -o build/tinygo$(EXE) -tags "byollvm osusergo" -ldflags="-X github.com/tinygo-org/tinygo/goenv.GitSha1=`git rev-parse --short HEAD`" .
+	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GOENVFLAGS) $(GO) build -buildmode exe -o build/tinygo$(EXE) -tags "byollvm osusergo" .
 test: wasi-libc check-nodejs-version
 	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) test $(GOTESTFLAGS) -timeout=1h -buildmode exe -tags "byollvm osusergo" $(GOTESTPKGS)
 

goenv/version.go

@@ -4,29 +4,47 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"runtime/debug"
 	"strings"
 )
 
 // Version of TinyGo.
 // Update this value before release of new version of software.
 const version = "0.35.0-dev"
 
-var (
-	// This variable is set at build time using -ldflags parameters.
-	// See: https://stackoverflow.com/a/11355611
-	GitSha1 string
-)
-
 // Return TinyGo version, either in the form 0.30.0 or as a development version
 // (like 0.30.0-dev-abcd012).
 func Version() string {
 	v := version
-	if strings.HasSuffix(version, "-dev") && GitSha1 != "" {
-		v += "-" + GitSha1
+	if strings.HasSuffix(version, "-dev") {
+		if hash := readGitHash(); hash != "" {
+			v += "-" + hash
+		}
 	}
 	return v
 }
 
+func readGitHash() string {
+	hash := ""
+	modified := false
+	if info, ok := debug.ReadBuildInfo(); ok {
+		for _, setting := range info.Settings {
+			println("setting:", setting.Key, setting.Value)
+			switch setting.Key {
+			case "vcs.revision":
+				hash = setting.Value[:8]
+			case "vcs.modified":
+				modified = setting.Value == "true"
+			}
+		}
+	}
+	value := hash
+	if value != "" && modified {
+		value += "-modified"
+	}
+	return value
+}
+
 // GetGorootVersion returns the major and minor version for a given GOROOT path.
 // If the goroot cannot be determined, (0, 0) is returned.
 func GetGorootVersion() (major, minor int, err error) {