Bin compat: use Platform.getFullExecutablePath instead of CommandLine.arguments.first for ProcessInfo.processName. (swiftlang#1411)

* Bin compat: use Platform.getFullExecutablePath instead of CommandLine.arguments.first for ProcessInfo.processName.

The original NSProcessInfo implementation calls _CFProcessPath for processName, which Platform.getFullExecutablePath internally calls. We should maintain the same behavior for binary compatibility.

* Update Platform.getFullExecutablePath implementation for Windows to match _CFProcessPath

Author: iCharlesHu

Sources/FoundationEssentials/Platform.swift

@@ -355,17 +355,14 @@ extension Platform {
         return try? FileManager.default.destinationOfSymbolicLink(
             atPath: "/proc/self/exe").standardizingPath
 #elseif os(Windows)
-        let hFile = GetModuleHandleW(nil)
-        let dwLength: DWORD = GetFinalPathNameByHandleW(hFile, nil, 0, FILE_NAME_NORMALIZED)
-        guard dwLength > 0 else { return nil }
-        return withUnsafeTemporaryAllocation(of: WCHAR.self, capacity: Int(dwLength)) { lpBuffer in
-            guard GetFinalPathNameByHandleW(hFile, lpBuffer.baseAddress, dwLength, FILE_NAME_NORMALIZED) == dwLength - 1 else {
+        return withUnsafeTemporaryAllocation(of: WCHAR.self, capacity: Int(MAX_PATH)) { lpBuffer in
+            let actualLength = GetModuleFileNameW(nil, lpBuffer.baseAddress!, DWORD(lpBuffer.count))
+            // Windows Documentation:
+            // If the function fails, the return value is 0 (zero).
+            // To get extended error information, call GetLastError.
+            guard actualLength > 0 else {
                 return nil
             }
-
-            // The `GetFinalPathNameByHandleW` function will normalise the path
-            // for us as part of the query. This allows us to avoid having to
-            // standardize the path ourselves.
             return String(decodingCString: lpBuffer.baseAddress!, as: UTF16.self)
         }
 #else

Sources/FoundationEssentials/ProcessInfo/ProcessInfo.swift

@@ -597,10 +597,7 @@ extension _ProcessInfo {
     }
 
     private static func _getProcessName() -> String {
-        guard let processPath = CommandLine.arguments.first else {
-            return ""
-        }
-        return processPath.lastPathComponent
+        return Platform.getFullExecutablePath()?.lastPathComponent ?? ""
     }
 
 #if os(macOS)