Fork#39268: g++ -O1 produces crashing code when accessing dlls via LoadLibrary()/GetProcAddress()/reinterpret_cast
Open Date: 2019-05-30 18:26
Last Update: 2019-05-30 23:07
URL for this Ticket:
https://osdn.net//projects/mingw/ticket/39268
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Last Changes/Comment on this Ticket:
2019-05-30 23:07 Updated by: keith
Comment:
Reply To comer352l
Reply To keith
Do please note that your c0000005 exception code is a SEGFAULT,
("access violation" in Microsoft parlance). This means that your
program is attempting to access memory to which it does not have access
rights. Likely causes are references to an uninitialized pointer, or to
memory which has already been deallocated; usually these are the result
of errors in the user program code, but unless you do provide a fully
self-contained test case, I am not willing to investigate further.
I know. But I'm pretty sure the code is correct.
Hmm. I'm not so sure. At a first quick glance, this looks odd:
1. extern "C" {
2. #include "windows.h"
3. }
• Firstly, (although GCC will tolerate it), the # introducing the include
directive really should not be anywhere other than in column one.
• Secondly, why use iquote semantics for "windows.h"? Is this the system
<windows.h>, or your own project-local header? (If the latter, then I would
suggest that the name is extremely badly chosen, because it conflicts with
the system header name).
• Thirdly, you should not embed the #include directive within the extern "C"
block scope; that scope should be correctly specified within the included
header itself, (and, in this case if it is the system's <windows.h>which is
being included, then this is certainly taken care of, because it is a C++
compatible C header).
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Ticket Status:
Reporter: comer352l
Owner: (None)
Type: Issues
Status: Open
Priority: 5 - Medium
MileStone: (None)
Component: (None)
Severity: 5 - Medium
Resolution: None
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Ticket details:
I'm investigating the following crash, which occurs when accessing a dll via
LoadLibrary(), getProcAddress(), reinterpret_cast:
Problem signature:
Problem Event Name: BEX
Application Name: test.exe
...
Fault Module Name: StackHash_0a9e
...
Exception Offset: 0028fe9c
Exception Code: c0000005
Exception Data: badc0de1
...
Additional Information 1: 0a9e
Additional Information 2: 0a9e372d3b4ad19135b953a78882e789
Additional Information 3: 0a9e
Additional Information 4: 0a9e372d3b4ad19135b953a78882e789
The code only crashes if it is compiled with -O1 (-O2, ...).
Moving around pieces of the code seems to fix the issue.
I was finally able to create some reduced example code with working / non
working variants (attachment follows).
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