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<div class="moz-cite-prefix">On 12/08/2022 15:55, Pedro Lamarão
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<div dir="ltr">Em sex., 12 de ago. de 2022 às 11:50, Maurizio
Cimadamore <<a href="mailto:maurizio.cimadamore@oracle.com" moz-do-not-send="true" class="moz-txt-link-freetext">maurizio.cimadamore@oracle.com</a>>
escreveu:<br>
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<div>On 12/08/2022 15:43, Pedro Lamarão wrote:<br>
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<div>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?</div>
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<div>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.</div>
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<div>This would be a blocker for all applications of
Windows API functions via panama.</div>
<div>Windows Sockets has a similar mechanism called
WSAGetLastError.</div>
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<p>And JNI - I doubt there's anything Panama specific here
(unless proven otherwise).</p>
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<div>Of course, this would disturb any interaction with
Windows API, however it was activated.</div>
<div>For some reason, such a debugger has been working with
software for some time, and I presume it works with software
that calls the system via JNI.</div>
<div>Is there perhaps some kind of special "locking" when
calling into JNI which the debugger might have learned to
respect?</div>
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<p>I think what we need at this point is some more testing.</p>
<p>E.g. can we reproduce the same issue with JNI? E.g. assume we
have a JNI binding for Windows API we want to call and a
_different_ JNI binding for checking LastError. Does that show the
same problem?</p>
<p>My gut feeling is that when writing this in JNI, developers would
have rolled in the LastError code check directly inside the native
code. And the native code execution is opaque to debuggers, so I
don't think a debugger could alter the LastError value seen by the
JNI native code.</p>
<p>But in this case there are _two_ calls, one to "WriteFile" and
one to "GetLastError". So the debugger would have plenty of
opportunities to make other system calls in between.</p>
<p>As I said, I believe this should be visible in JNI too - but
perhaps nobody would write code like this using JNI. E.g. with
JNI, since it's painful enough to write one native method,
developers tend to "lump" multiple functionalities, e.g. error
checking, in the same native method implementation. Which,
coincidentally, bypasses some issues that might be visible when
using debuggers (so it is possible that this is a problem that
debuggers never had to worry too much about).<br>
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<p>Maurizio<br>
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-- <br>
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<div>Pedro Lamarão</div>
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