GetLastError() (with and without debugger)

[Maurizio Cimadamore]

On 12/08/2022 15:43, Pedro Lamarão wrote:
>
>     This is incorrect. WriteFile() indicates an error, but
>     GetLastError() returns 0 (= NO_ERROR). Could it be that the
>     debugger calls another Windows API function between those two
>     functions, resetting the last error?
>
>     In my project that's a major issue. Since the software behaves
>     incorrectly with the debugger, the software can no longer be
>     debugged. This doesn't just affect it when debugging this
>     particular piece of code but anytime this code is run in a
>     debugging session.
>
>
>
> This would be a blocker for all applications of Windows API functions 
> via panama.
> Windows Sockets has a similar mechanism called WSAGetLastError.

And JNI - I doubt there's anything Panama specific here (unless proven 
otherwise).

So that it's clear - it's not that GetLastError fails in general. It 
fails when a debugger is attached. As I explained, this could be due to 
_which_ debugger is attached, or some existing issue (predating Panama) 
in the way jdb/JPDA deal with some Windows system calls.

Maurizio

>
> As far as I know, GetLastError and WSAGetLastError are getter-like 
> functions for effectively thread local data.
> It is safe to call Windows API functions from inside the same process 
> but another thread.
> If some piece of software infrastructure has perturbed your program, 
> then it has called a Windows API function from inside our program
>
>     Is there something I'm not doing incorrectly? Or is there a fix or
>     workaround?
>
>     Here's the Java code:
>
>     import java.lang.foreign.*; import java.lang.invoke.MethodHandle; import static java.lang.foreign.MemoryAddress.NULL; import static java.lang.foreign.ValueLayout.ADDRESS; import static java.lang.foreign.ValueLayout.JAVA_INT; public class WinApi {
>          static final MethodHandleWriteFile$Func; static final MethodHandleGetLastError$Func; static final MemoryAddressINVALID_HANDLE_VALUE = MemoryAddress.ofLong(-1); static {
>              var linker = Linker.nativeLinker(); var lookup = SymbolLookup.libraryLookup("Kernel32", MemorySession.global()); WriteFile$Func = linker.downcallHandle(
>                      lookup.lookup("WriteFile").get(), FunctionDescriptor.of(JAVA_INT, ADDRESS, ADDRESS, JAVA_INT, ADDRESS, ADDRESS)
>              ); GetLastError$Func = linker.downcallHandle(
>                      lookup.lookup("GetLastError").get(), FunctionDescriptor.of(JAVA_INT)
>              ); }
>
>          public static void main(String[] args) {
>              var res =WriteFile(INVALID_HANDLE_VALUE, NULL, 0, NULL, NULL); var err =GetLastError(); System.out.printf("WriteFile result: %d, GetLastError result: %d\n", res, err); }
>
>          static int WriteFile(MemoryAddress hFile, MemoryAddress lpBuffer, int nNumberOfBytesToWrite, MemoryAddress lpNumberOfBytesWritten, MemoryAddress lpOverlapped) {
>              try {
>                  return (int)WriteFile$Func.invokeExact((Addressable)hFile, (Addressable)lpBuffer, nNumberOfBytesToWrite, (Addressable)lpNumberOfBytesWritten, (Addressable)lpOverlapped); }catch (Throwable e) {
>                  throw new RuntimeException(e); }
>          }
>
>          static int GetLastError() {
>              try {
>                  return (int)GetLastError$Func.invokeExact(); }catch (Throwable e) {
>                  throw new RuntimeException(e); }
>          }
>     }
>
>
>     Cheers
>     Manuel
>
>
>
>
> -- 
> Pedro Lamarão
> https://www.prodist.com.br
> Securing Critical Systems
> Tel: +55 11 4380-6585
>
> Antes de imprimir esta mensagem e seus anexos, certifique-se que seja 
> realmente necessário.
> Proteger o meio ambiente é nosso dever.
> Before printing this e-mail or attachments, be sure it is necessary.
> It is in our hands to protect the environment.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/panama-dev/attachments/20220812/85e525b1/attachment-0001.htm>