builder: refactor clang include headers

Set -resource-dir in a central place instead of passing the header path
around everywhere and adding it using the `-I` flag. I believe this is
closer to how Clang is intended to be used.

This change was inspired by my attempt to add a Nix flake file to
TinyGo.

builder/build.go

@@ -211,7 +211,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 	defer machine.Dispose()
 
 	// Load entire program AST into memory.
-	lprogram, err := loader.Load(config, pkgName, config.ClangHeaders, types.Config{
+	lprogram, err := loader.Load(config, pkgName, types.Config{
 		Sizes: compiler.Sizes(machine),
 	})
 	if err != nil {
@@ -662,7 +662,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 		job := &compileJob{
 			description: "compile extra file " + path,
 			run: func(job *compileJob) error {
-				result, err := compileAndCacheCFile(abspath, tmpdir, config.CFlags(), config.Options.PrintCommands)
+				result, err := compileAndCacheCFile(abspath, tmpdir, config.CFlags(false), config.Options.PrintCommands)
 				job.result = result
 				return err
 			},

builder/builder_test.go

@@ -8,7 +8,6 @@ import (
 	"testing"
 
 	"github.com/tinygo-org/tinygo/compileopts"
-	"github.com/tinygo-org/tinygo/goenv"
 	"tinygo.org/x/go-llvm"
 )
 
@@ -74,7 +73,6 @@ func TestClangAttributes(t *testing.T) {
 
 func testClangAttributes(t *testing.T, options *compileopts.Options) {
 	testDir := t.TempDir()
-	clangHeaderPath := getClangHeaderPath(goenv.Get("TINYGOROOT"))
 
 	ctx := llvm.NewContext()
 	defer ctx.Dispose()
@@ -84,9 +82,8 @@ func testClangAttributes(t *testing.T, options *compileopts.Options) {
 		t.Fatalf("could not load target: %s", err)
 	}
 	config := compileopts.Config{
-		Options:      options,
-		Target:       target,
-		ClangHeaders: clangHeaderPath,
+		Options: options,
+		Target:  target,
 	}
 
 	// Create a very simple C input file.
@@ -98,7 +95,7 @@ func testClangAttributes(t *testing.T, options *compileopts.Options) {
 
 	// Compile this file using Clang.
 	outpath := filepath.Join(testDir, "test.bc")
-	flags := append([]string{"-c", "-emit-llvm", "-o", outpath, srcpath}, config.CFlags()...)
+	flags := append([]string{"-c", "-emit-llvm", "-o", outpath, srcpath}, config.CFlags(false)...)
 	if config.GOOS() == "darwin" {
 		// Silence some warnings that happen when testing GOOS=darwin on
 		// something other than MacOS.

builder/config.go

@@ -33,13 +33,10 @@ func NewConfig(options *compileopts.Options) (*compileopts.Config, error) {
 		return nil, fmt.Errorf("requires go version 1.18 through 1.21, got go%d.%d", major, minor)
 	}
 
-	clangHeaderPath := getClangHeaderPath(goenv.Get("TINYGOROOT"))
-
 	return &compileopts.Config{
 		Options:        options,
 		Target:         spec,
 		GoMinorVersion: minor,
-		ClangHeaders:   clangHeaderPath,
 		TestConfig:     options.TestConfig,
 	}, nil
 }

builder/env.go

@@ -1,105 +0,0 @@
-package builder
-
-import (
-	"errors"
-	"io/fs"
-	"io/ioutil"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"sort"
-	"strings"
-
-	"tinygo.org/x/go-llvm"
-)
-
-// getClangHeaderPath returns the path to the built-in Clang headers. It tries
-// multiple locations, which should make it find the directory when installed in
-// various ways.
-func getClangHeaderPath(TINYGOROOT string) string {
-	// Check whether we're running from the source directory.
-	path := filepath.Join(TINYGOROOT, "llvm-project", "clang", "lib", "Headers")
-	if _, err := os.Stat(path); !errors.Is(err, fs.ErrNotExist) {
-		return path
-	}
-
-	// Check whether we're running from the installation directory.
-	path = filepath.Join(TINYGOROOT, "lib", "clang", "include")
-	if _, err := os.Stat(path); !errors.Is(err, fs.ErrNotExist) {
-		return path
-	}
-
-	// It looks like we are built with a system-installed LLVM. Do a last
-	// attempt: try to use Clang headers relative to the clang binary.
-	llvmMajor := strings.Split(llvm.Version, ".")[0]
-	for _, cmdName := range commands["clang"] {
-		binpath, err := exec.LookPath(cmdName)
-		if err == nil {
-			// This should be the command that will also be used by
-			// execCommand. To avoid inconsistencies, make sure we use the
-			// headers relative to this command.
-			binpath, err = filepath.EvalSymlinks(binpath)
-			if err != nil {
-				// Unexpected.
-				return ""
-			}
-			// Example executable:
-			//     /usr/lib/llvm-9/bin/clang
-			// Example include path:
-			//     /usr/lib/llvm-9/lib64/clang/9.0.1/include/
-			llvmRoot := filepath.Dir(filepath.Dir(binpath))
-			clangVersionRoot := filepath.Join(llvmRoot, "lib64", "clang")
-			dirs64, err64 := ioutil.ReadDir(clangVersionRoot)
-			// Example include path:
-			//     /usr/lib/llvm-9/lib/clang/9.0.1/include/
-			clangVersionRoot = filepath.Join(llvmRoot, "lib", "clang")
-			dirs32, err32 := ioutil.ReadDir(clangVersionRoot)
-			if err64 != nil && err32 != nil {
-				// Unexpected.
-				continue
-			}
-			dirnames := make([]string, len(dirs64)+len(dirs32))
-			dirCount := 0
-			for _, d := range dirs32 {
-				name := d.Name()
-				if name == llvmMajor || strings.HasPrefix(name, llvmMajor+".") {
-					dirnames[dirCount] = filepath.Join(llvmRoot, "lib", "clang", name)
-					dirCount++
-				}
-			}
-			for _, d := range dirs64 {
-				name := d.Name()
-				if name == llvmMajor || strings.HasPrefix(name, llvmMajor+".") {
-					dirnames[dirCount] = filepath.Join(llvmRoot, "lib64", "clang", name)
-					dirCount++
-				}
-			}
-			sort.Strings(dirnames)
-			// Check for the highest version first.
-			for i := dirCount - 1; i >= 0; i-- {
-				path := filepath.Join(dirnames[i], "include")
-				_, err := os.Stat(filepath.Join(path, "stdint.h"))
-				if err == nil {
-					return path
-				}
-			}
-		}
-	}
-
-	// On Arch Linux, the clang executable is stored in /usr/bin rather than being symlinked from there.
-	// Search directly in /usr/lib for clang.
-	if matches, err := filepath.Glob("/usr/lib/clang/" + llvmMajor + ".*.*"); err == nil {
-		// Check for the highest version first.
-		sort.Strings(matches)
-		for i := len(matches) - 1; i >= 0; i-- {
-			path := filepath.Join(matches[i], "include")
-			_, err := os.Stat(filepath.Join(path, "stdint.h"))
-			if err == nil {
-				return path
-			}
-		}
-	}
-
-	// Could not find it.
-	return ""
-}

builder/library.go

@@ -143,6 +143,10 @@ func (l *Library) load(config *compileopts.Config, tmpdir string) (job *compileJ
 	// reproducible. Otherwise the temporary directory is stored in the archive
 	// itself, which varies each run.
 	args := append(l.cflags(target, headerPath), "-c", "-Oz", "-gdwarf-4", "-ffunction-sections", "-fdata-sections", "-Wno-macro-redefined", "--target="+target, "-fdebug-prefix-map="+dir+"="+remapDir)
+	resourceDir := goenv.ClangResourceDir(false)
+	if resourceDir != "" {
+		args = append(args, "-resource-dir="+resourceDir)
+	}
 	cpu := config.CPU()
 	if cpu != "" {
 		// X86 has deprecated the -mcpu flag, so we need to use -march instead.

builder/tools.go

@@ -1,7 +1,6 @@
 package builder
 
 import (
-	"errors"
 	"os"
 	"os/exec"
 
@@ -12,11 +11,6 @@ import (
 func runCCompiler(flags ...string) error {
 	if hasBuiltinTools {
 		// Compile this with the internal Clang compiler.
-		headerPath := getClangHeaderPath(goenv.Get("TINYGOROOT"))
-		if headerPath == "" {
-			return errors.New("could not locate Clang headers")
-		}
-		flags = append(flags, "-I"+headerPath)
 		cmd := exec.Command(os.Args[0], append([]string{"clang"}, flags...)...)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr