dlfcn: rework error check (ebitengine#119)

eliottness · Eliott Bouhana · web-flow · commit bfe9e39de4ce · 2023-03-31T00:15:47.000+09:00
Closes ebitengine#118 Signed-off-by: Eliott Bouhana <eliott.bouhana@datadoghq.fr> Co-authored-by: Eliott Bouhana <eliott.bouhana@datadoghq.fr>
diff --git a/callback_test.go b/callback_test.go
@@ -31,7 +31,7 @@ func TestCallGoFromSharedLib(t *testing.T) {
 
 	lib, err := purego.Dlopen(libFileName, purego.RTLD_NOW|purego.RTLD_GLOBAL)
 	if err != nil {
-		t.Fatalf("Dlopen(%q) faled: %v", libFileName, err)
+		t.Fatalf("Dlopen(%q) failed: %v", libFileName, err)
 	}
 
 	var callCallback func(p uintptr, s string) int
diff --git a/dlfcn.go b/dlfcn.go
@@ -35,8 +35,8 @@ func init() {
 // Dlopen calls should be balanced with a Dlclose call.
 func Dlopen(path string, mode int) (uintptr, error) {
 	u := fnDlopen(path, mode)
-	if errStr := fnDlerror(); errStr != "" {
-		return 0, Dlerror{errStr}
+	if u == 0 {
+		return 0, Dlerror{fnDlerror()}
 	}
 	return u, nil
 }
@@ -47,8 +47,8 @@ func Dlopen(path string, mode int) (uintptr, error) {
 // when that library was loaded, Dlsym returns zero.
 func Dlsym(handle uintptr, name string) (uintptr, error) {
 	u := fnDlsym(handle, name)
-	if errStr := fnDlerror(); errStr != "" {
-		return 0, Dlerror{errStr}
+	if u == 0 {
+		return 0, Dlerror{fnDlerror()}
 	}
 	return u, nil
 }
diff --git a/dlfcn_test.go b/dlfcn_test.go
@@ -7,7 +7,11 @@ package purego_test
 
 import (
 	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 	"unsafe"
 
@@ -90,3 +94,32 @@ func Test_qsort(t *testing.T) {
 		}
 	}
 }
+
+func TestNestedDlopenCall(t *testing.T) {
+	libFileName := filepath.Join(t.TempDir(), "libdlnested.so")
+	t.Logf("Build %v", libFileName)
+
+	out, err := exec.Command("go", "env", "CXX").Output()
+	if err != nil {
+		t.Fatalf("go env error: %v", err)
+	}
+
+	cxx := strings.TrimSpace(string(out))
+	if cxx == "" {
+		t.Fatal("CXX not found")
+	}
+
+	args := []string{"-shared", "-Wall", "-Werror", "-o", libFileName, filepath.Join("libdlnested", "nested.cpp")}
+	cmd := exec.Command(cxx, args...)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("compile lib: %v\n%q\n%s", err, cmd, string(out))
+	}
+	defer os.Remove(libFileName)
+
+	lib, err := purego.Dlopen(libFileName, purego.RTLD_NOW|purego.RTLD_GLOBAL)
+	if err != nil {
+		t.Fatalf("Dlopen(%q) failed: %v", libFileName, err)
+	}
+
+	purego.Dlclose(lib)
+}
diff --git a/libdlnested/nested.cpp b/libdlnested/nested.cpp
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 The Ebitengine Authors
+
+#include <dlfcn.h>
+
+struct nested_libdl
+{
+    nested_libdl() {
+        // Fails for sure because a symbol cannot be named like this 
+        dlsym(RTLD_DEFAULT, "@/*<>");
+    }
+};
+
+static nested_libdl test;

Original file line number	Diff line number	Diff line change
`@@ -31,7 +31,7 @@ func TestCallGoFromSharedLib(t *testing.T) {`
`31`	`31`
`32`	`32`	`lib, err := purego.Dlopen(libFileName, purego.RTLD_NOW\|purego.RTLD_GLOBAL)`
`33`	`33`	`if err != nil {`
`34`		`- t.Fatalf("Dlopen(%q) faled: %v", libFileName, err)`
	`34`	`+ t.Fatalf("Dlopen(%q) failed: %v", libFileName, err)`
`35`	`35`	`}`
`36`	`36`
`37`	`37`	`var callCallback func(p uintptr, s string) int`
Original file line number	Diff line number	Diff line change
`@@ -35,8 +35,8 @@ func init() {`
`35`	`35`	`// Dlopen calls should be balanced with a Dlclose call.`
`36`	`36`	`func Dlopen(path string, mode int) (uintptr, error) {`
`37`	`37`	`u := fnDlopen(path, mode)`
`38`		`- if errStr := fnDlerror(); errStr != "" {`
`39`		`- return 0, Dlerror{errStr}`
	`38`	`+ if u == 0 {`
	`39`	`+ return 0, Dlerror{fnDlerror()}`
`40`	`40`	`}`
`41`	`41`	`return u, nil`
`42`	`42`	`}`
`@@ -47,8 +47,8 @@ func Dlopen(path string, mode int) (uintptr, error) {`
`47`	`47`	`// when that library was loaded, Dlsym returns zero.`
`48`	`48`	`func Dlsym(handle uintptr, name string) (uintptr, error) {`
`49`	`49`	`u := fnDlsym(handle, name)`
`50`		`- if errStr := fnDlerror(); errStr != "" {`
`51`		`- return 0, Dlerror{errStr}`
	`50`	`+ if u == 0 {`
	`51`	`+ return 0, Dlerror{fnDlerror()}`
`52`	`52`	`}`
`53`	`53`	`return u, nil`
`54`	`54`	`}`