[android] fix the android build

Platform.swift regressed after 71eefee

Author: hyp

Sources/FoundationEssentials/Platform.swift

@@ -29,8 +29,7 @@ fileprivate let _pageSize: Int = {
 // WebAssembly defines a fixed page size
 fileprivate let _pageSize: Int = 65_536
 #elseif canImport(Android)
-import Bionic
-import unistd
+import Android
 fileprivate let _pageSize: Int = Int(getpagesize())
 #elseif canImport(Glibc)
 import Glibc
@@ -142,7 +141,7 @@ extension Platform {
     typealias Operation<Input, Output> = (Input, UnsafeMutablePointer<Output>, UnsafeMutablePointer<CChar>, Int, UnsafeMutablePointer<UnsafeMutablePointer<Output>?>) -> Int32
     #endif
 
-    private static func withUserGroupBuffer<Input, Output, R>(_ input: Input, _ output: Output, sizeProperty: Int32, operation: Operation<Input, Output>, block: (Output) throws -> R) rethrows -> R? {
+    private static func withUserGroupBuffer<Input, Output, R>(_ input: Input, _ output: Output, sizeProperty: Int32, operation: Operation<Input, Output>, block: (Output) throws -> R?) rethrows -> R? {
         var bufferLen = sysconf(sizeProperty)
         if bufferLen == -1 {
             bufferLen = 4096 // Generous default size estimate
@@ -172,31 +171,51 @@ extension Platform {
 
     static func name(forUID uid: uid_t) -> String? {
         withUserGroupBuffer(uid, passwd(), sizeProperty: Int32(_SC_GETPW_R_SIZE_MAX), operation: getpwuid_r) {
-            String(cString: $0.pw_name)
+            // Android's pw_name `char *`` is nullable, so always coerce to a nullable pointer
+            // in order to be compatible with Android.
+            let pw_name: UnsafeMutablePointer<CChar>? = $0.pw_name
+            return pw_name.flatMap { String(cString: $0) }
         }
     }
 
     static func fullName(forUID uid: uid_t) -> String? {
         withUserGroupBuffer(uid, passwd(), sizeProperty: Int32(_SC_GETPW_R_SIZE_MAX), operation: getpwuid_r) {
-            String(cString: $0.pw_gecos)
+#if os(Android) && (arch(i386) || arch(arm))
+            // pw_gecos isn't available on 32-bit Android.
+            let pw_gecos: UnsafeMutablePointer<CChar>? = nil
+#else
+            // Android's pw_gecos `char *`` is nullable, so always coerce to a nullable pointer
+            // in order to be compatible with Android.
+            let pw_gecos: UnsafeMutablePointer<CChar>? = $0.pw_gecos
+#endif
+            return pw_gecos.flatMap { String(cString: $0) }
         }
     }
 
     static func name(forGID gid: gid_t) -> String? {
         withUserGroupBuffer(gid, group(), sizeProperty: Int32(_SC_GETGR_R_SIZE_MAX), operation: getgrgid_r) {
-            String(cString: $0.gr_name)
+            // Android's gr_name `char *`` is nullable, so always coerce to a nullable pointer
+            // in order to be compatible with Android.
+            let gr_name: UnsafeMutablePointer<CChar>? = $0.gr_name
+            return gr_name.flatMap { String(cString: $0) }
         }
     }
 
     static func homeDirectory(forUserName userName: String) -> String? {
         withUserGroupBuffer(userName, passwd(), sizeProperty: Int32(_SC_GETPW_R_SIZE_MAX), operation: getpwnam_r) {
-            String(cString: $0.pw_dir)
+            // Android's pw_dir `char *`` is nullable, so always coerce to a nullable pointer
+            // in order to be compatible with Android.
+            let pw_dir: UnsafeMutablePointer<CChar>? = $0.pw_dir
+            return pw_dir.flatMap { String(cString: $0) }
         }
     }
 
     static func homeDirectory(forUID uid: uid_t) -> String? {
         withUserGroupBuffer(uid, passwd(), sizeProperty: Int32(_SC_GETPW_R_SIZE_MAX), operation: getpwuid_r) {
-            String(cString: $0.pw_dir)
+            // Android's pw_dir `char *`` is nullable, so always coerce to a nullable pointer
+            // in order to be compatible with Android.
+            let pw_dir: UnsafeMutablePointer<CChar>? = $0.pw_dir
+            return pw_dir.flatMap { String(cString: $0) }
         }
     }
 }