build: support pkg-config and link args

internal/build/build.go

@@ -34,6 +34,8 @@ import (
 	"github.com/goplus/llgo/cl"
 	"github.com/goplus/llgo/internal/packages"
 	"github.com/goplus/llgo/xtool/clang"
+	clangCheck "github.com/goplus/llgo/xtool/clang/check"
+	"github.com/goplus/llgo/xtool/env"
 
 	llssa "github.com/goplus/llgo/ssa"
 )
@@ -207,11 +209,33 @@ func buildAllPkgs(prog llssa.Program, initial []*packages.Package, mode Mode, ve
 				pkg.ExportFile = ""
 			}
 			if kind == cl.PkgLinkExtern { // need to be linked with external library
-				linkFile := os.ExpandEnv(strings.TrimSpace(param))
-				dir, lib := filepath.Split(linkFile)
-				command := " -l " + lib
-				if dir != "" {
-					command += " -L " + dir[:len(dir)-1]
+				// format: ';' separated alternative link methods. e.g.
+				//   link: $LLGO_LIB_PYTHON; $(pkg-config --libs python3-embed); -lpython3
+				expd := ""
+				altParts := strings.Split(param, ";")
+				for _, param := range altParts {
+					expd = strings.TrimSpace(env.ExpandEnv(strings.TrimSpace(param)))
+					if len(expd) > 0 {
+						break
+					}
+				}
+				if expd == "" {
+					panic(fmt.Sprintf("'%s' cannot locate the external library", param))
+				}
+
+				command := ""
+				if expd[0] == '-' {
+					command += " " + expd
+				} else {
+					linkFile := expd
+					dir, lib := filepath.Split(linkFile)
+					command = " -l " + lib
+					if dir != "" {
+						command += " -L " + dir[:len(dir)-1]
+					}
+				}
+				if err := clangCheck.CheckLinkArgs(command); err != nil {
+					panic(fmt.Sprintf("test link args '%s' failed\n\texpanded to: %s\n\tresolved to: %v\n\terror: %v", param, expd, command, err))
 				}
 				if isSingleLinkFile(pkg.ExportFile) {
 					pkg.ExportFile = command + " " + pkg.ExportFile

py/python.go

@@ -23,7 +23,7 @@ import (
 )
 
 const (
-	LLGoPackage = "link: $LLGO_LIB_PYTHON"
+	LLGoPackage = "link: $LLGO_LIB_PYTHON; $(pkg-config --libs python3-embed)"
 )
 
 // -----------------------------------------------------------------------------

xtool/clang/check/check.go

@@ -0,0 +1,26 @@
+package check
+
+import (
+	"errors"
+	"os/exec"
+	"runtime"
+	"strings"
+)
+
+func CheckLinkArgs(args string) error {
+	cmdArgs := strings.Split(args, " ")
+	cmd := exec.Command("clang")
+	nul := "/dev/null"
+	if runtime.GOOS == "windows" {
+		nul = "NUL"
+	}
+	cmd.Args = append(cmd.Args, cmdArgs...)
+	cmd.Args = append(cmd.Args, "-x", "c", "-o", nul, "-")
+	src := "int main() {return 0;}"
+	srcIn := strings.NewReader(src)
+	cmd.Stdin = srcIn
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return errors.New(string(out))
+	}
+	return nil
+}

xtool/env/env.go

@@ -0,0 +1,32 @@
+package env
+
+import (
+	"os"
+	"os/exec"
+	"regexp"
+	"runtime"
+	"strings"
+)
+
+func ExpandEnv(s string) string {
+	return expandEnvWithCmd(s)
+}
+
+func expandEnvWithCmd(s string) string {
+	re := regexp.MustCompile(`\$\(([^)]+)\)`)
+	expanded := re.ReplaceAllStringFunc(s, func(m string) string {
+		cmd := re.FindStringSubmatch(m)[1]
+		var out []byte
+		var err error
+		if runtime.GOOS == "windows" {
+			out, err = exec.Command("cmd", "/C", cmd).Output()
+		} else {
+			out, err = exec.Command("sh", "-c", cmd).Output()
+		}
+		if err != nil {
+			return ""
+		}
+		return strings.TrimSpace(string(out))
+	})
+	return os.Expand(expanded, os.Getenv)
+}