Call C dlfcn functions directly on android (#263)

dlfcn.go

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: 2022 The Ebitengine Authors
 
-//go:build (darwin || freebsd || linux) && !faketime
+//go:build (darwin || freebsd || linux) && !android && !faketime
 
 package purego
 

dlfcn_android.go

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2024 The Ebitengine Authors
+
+package purego
+
+import "github.com/ebitengine/purego/internal/cgo"
+
+// Source for constants: https://android.googlesource.com/platform/bionic/+/refs/heads/main/libc/include/dlfcn.h
+
+const (
+	is64bit      = 1 << (^uintptr(0) >> 63) / 2
+	is32bit      = 1 - is64bit
+	RTLD_DEFAULT = is32bit * 0xffffffff
+	RTLD_LAZY    = 0x00000001
+	RTLD_NOW     = is64bit * 0x00000002
+	RTLD_LOCAL   = 0x00000000
+	RTLD_GLOBAL  = is64bit*0x00100 | is32bit*0x00000002
+)
+
+func Dlopen(path string, mode int) (uintptr, error) {
+	return cgo.Dlopen(path, mode)
+}
+
+func Dlsym(handle uintptr, name string) (uintptr, error) {
+	return cgo.Dlsym(handle, name)
+}
+
+func Dlclose(handle uintptr) error {
+	return cgo.Dlclose(handle)
+}
+
+func loadSymbol(handle uintptr, name string) (uintptr, error) {
+	return Dlsym(handle, name)
+}

dlfcn_darwin.go

@@ -6,11 +6,11 @@ package purego
 // Source for constants: https://opensource.apple.com/source/dyld/dyld-360.14/include/dlfcn.h.auto.html
 
 const (
-	RTLD_DEFAULT = ^uintptr(0) - 1 // Pseudo-handle for dlsym so search for any loaded symbol
-	RTLD_LAZY    = 0x1             // Relocations are performed at an implementation-dependent time.
-	RTLD_NOW     = 0x2             // Relocations are performed when the object is loaded.
-	RTLD_LOCAL   = 0x4             // All symbols are not made available for relocation processing by other modules.
-	RTLD_GLOBAL  = 0x8             // All symbols are available for relocation processing of other modules.
+	RTLD_DEFAULT = 1<<64 - 2 // Pseudo-handle for dlsym so search for any loaded symbol
+	RTLD_LAZY    = 0x1       // Relocations are performed at an implementation-dependent time.
+	RTLD_NOW     = 0x2       // Relocations are performed when the object is loaded.
+	RTLD_LOCAL   = 0x4       // All symbols are not made available for relocation processing by other modules.
+	RTLD_GLOBAL  = 0x8       // All symbols are available for relocation processing of other modules.
 )
 
 //go:cgo_import_dynamic purego_dlopen dlopen "/usr/lib/libSystem.B.dylib"

dlfcn_freebsd.go

@@ -5,9 +5,10 @@ package purego
 
 // Constants as defined in https://github.com/freebsd/freebsd-src/blob/main/include/dlfcn.h
 const (
-	RTLD_DEFAULT = ^uintptr(0) - 2 // Pseudo-handle for dlsym so search for any loaded symbol
-	RTLD_LAZY    = 0x00001         // Relocations are performed at an implementation-dependent time.
-	RTLD_NOW     = 0x00002         // Relocations are performed when the object is loaded.
-	RTLD_LOCAL   = 0x00000         // All symbols are not made available for relocation processing by other modules.
-	RTLD_GLOBAL  = 0x00100         // All symbols are available for relocation processing of other modules.
+	intSize      = 32 << (^uint(0) >> 63) // 32 or 64
+	RTLD_DEFAULT = 1<<intSize - 2         // Pseudo-handle for dlsym so search for any loaded symbol
+	RTLD_LAZY    = 0x00000001             // Relocations are performed at an implementation-dependent time.
+	RTLD_NOW     = 0x00000002             // Relocations are performed when the object is loaded.
+	RTLD_LOCAL   = 0x00000000             // All symbols are not made available for relocation processing by other modules.
+	RTLD_GLOBAL  = 0x00000100             // All symbols are available for relocation processing of other modules.
 )

dlfcn_linux.go

@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: 2022 The Ebitengine Authors
 
+//go:build !android
+
 package purego
 
 // Source for constants: https://codebrowser.dev/glibc/glibc/bits/dlfcn.h.html

func.go

@@ -152,6 +152,7 @@ func RegisterFunc(fptr interface{}, cfn uintptr) {
 					stack++
 				}
 			case reflect.Float32, reflect.Float64:
+				const is32bit = unsafe.Sizeof(uintptr(0)) == 4
 				if is32bit {
 					panic("purego: floats only supported on 64bit platforms")
 				}
@@ -417,8 +418,6 @@ func checkStructFieldsSupported(ty reflect.Type) {
 	}
 }
 
-const is32bit = unsafe.Sizeof(uintptr(0)) == 4
-
 func roundUpTo8(val uintptr) uintptr {
 	return (val + 7) &^ 7
 }

internal/cgo/dlfcn_cgo_unix.go

@@ -9,9 +9,43 @@ package cgo
  #cgo LDFLAGS: -ldl
 
 #include <dlfcn.h>
+#include <stdlib.h>
 */
 import "C"
 
+import (
+	"errors"
+	"unsafe"
+)
+
+func Dlopen(filename string, flag int) (uintptr, error) {
+	cfilename := C.CString(filename)
+	defer C.free(unsafe.Pointer(cfilename))
+	handle := C.dlopen(cfilename, C.int(flag))
+	if handle == nil {
+		return 0, errors.New(C.GoString(C.dlerror()))
+	}
+	return uintptr(handle), nil
+}
+
+func Dlsym(handle uintptr, symbol string) (uintptr, error) {
+	csymbol := C.CString(symbol)
+	defer C.free(unsafe.Pointer(csymbol))
+	symbolAddr := C.dlsym(*(*unsafe.Pointer)(unsafe.Pointer(&handle)), csymbol)
+	if symbolAddr == nil {
+		return 0, errors.New(C.GoString(C.dlerror()))
+	}
+	return uintptr(symbolAddr), nil
+}
+
+func Dlclose(handle uintptr) error {
+	result := C.dlclose(*(*unsafe.Pointer)(unsafe.Pointer(&handle)))
+	if result != 0 {
+		return errors.New(C.GoString(C.dlerror()))
+	}
+	return nil
+}
+
 // all that is needed is to assign each dl function because then its
 // symbol will then be made available to the linker and linked to inside dlfcn.go
 var (