GetMessage Win API function throws exception (probably due to a wrong callback)
My problem I think that is due to the fact that I try to bind a class member function (not static) as a callback to the SetWindowsHookEx function. I've tried debugging but I was unable to get any other useful info except the callback binding which I'm not aware of any other way of doing so.
Therefore, at the first call of the GetMessage function I receive the following exception: An unhandled exception was encountered during a user callback. .
My question is, if the cause of the exception is the way I'm binding the HookLowLevel::KeyboardProc function so I can pass it as a callback, what's the right way of doing so? If not, what do you think may be the cause of the exception being thrown?
The function inside which I'm doing the callback binding and where the GetMessage function that throws the exception is found:
void HookLowLevel::attachHook()
{
printf("Hooking the keyboardn");
auto callback = std::bind(&HookLowLevel::KeyboardProc, this);
hook_ = SetWindowsHookEx(WH_KEYBOARD_LL, (HOOKPROC)(&callback), 0, 0);
printf("%Xn", hook_);
MSG msg{ 0 };
try
{
while (GetMessage(&msg, NULL, 0, 0) != 0 && !windowChanged_)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
catch (const std::runtime_error& re)
{
std::cerr << "Runtime error: " << re.what() << std::endl;
}
catch (const std::exception &e)
{
std::cerr << "exception: " << e.what();
}
}
And this is how the definition of the KeyboardProc looks like:
LRESULT CALLBACK HookLowLevel::KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
c++ winapi boost
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
add a comment |
My problem I think that is due to the fact that I try to bind a class member function (not static) as a callback to the SetWindowsHookEx function. I've tried debugging but I was unable to get any other useful info except the callback binding which I'm not aware of any other way of doing so.
Therefore, at the first call of the GetMessage function I receive the following exception: An unhandled exception was encountered during a user callback. .
My question is, if the cause of the exception is the way I'm binding the HookLowLevel::KeyboardProc function so I can pass it as a callback, what's the right way of doing so? If not, what do you think may be the cause of the exception being thrown?
The function inside which I'm doing the callback binding and where the GetMessage function that throws the exception is found:
void HookLowLevel::attachHook()
{
printf("Hooking the keyboardn");
auto callback = std::bind(&HookLowLevel::KeyboardProc, this);
hook_ = SetWindowsHookEx(WH_KEYBOARD_LL, (HOOKPROC)(&callback), 0, 0);
printf("%Xn", hook_);
MSG msg{ 0 };
try
{
while (GetMessage(&msg, NULL, 0, 0) != 0 && !windowChanged_)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
catch (const std::runtime_error& re)
{
std::cerr << "Runtime error: " << re.what() << std::endl;
}
catch (const std::exception &e)
{
std::cerr << "exception: " << e.what();
}
}
And this is how the definition of the KeyboardProc looks like:
LRESULT CALLBACK HookLowLevel::KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
c++ winapi boost
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
Remove the cast toHOOKPROC, and so your function call becomesSetWindowsHookEx(WH_KEYBOARD_LL, callback, 0, 0);Does this compile? If it does not, thencallbackis not of the correct signature. No amount of casting can change that. The cast toHOOKPROCin your code would merely be a means for you to tell a big fat lie to the compiler. Those lies seldom end well.
– David Heffernan
Nov 15 '18 at 10:05
add a comment |
My problem I think that is due to the fact that I try to bind a class member function (not static) as a callback to the SetWindowsHookEx function. I've tried debugging but I was unable to get any other useful info except the callback binding which I'm not aware of any other way of doing so.
Therefore, at the first call of the GetMessage function I receive the following exception: An unhandled exception was encountered during a user callback. .
My question is, if the cause of the exception is the way I'm binding the HookLowLevel::KeyboardProc function so I can pass it as a callback, what's the right way of doing so? If not, what do you think may be the cause of the exception being thrown?
The function inside which I'm doing the callback binding and where the GetMessage function that throws the exception is found:
void HookLowLevel::attachHook()
{
printf("Hooking the keyboardn");
auto callback = std::bind(&HookLowLevel::KeyboardProc, this);
hook_ = SetWindowsHookEx(WH_KEYBOARD_LL, (HOOKPROC)(&callback), 0, 0);
printf("%Xn", hook_);
MSG msg{ 0 };
try
{
while (GetMessage(&msg, NULL, 0, 0) != 0 && !windowChanged_)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
catch (const std::runtime_error& re)
{
std::cerr << "Runtime error: " << re.what() << std::endl;
}
catch (const std::exception &e)
{
std::cerr << "exception: " << e.what();
}
}
And this is how the definition of the KeyboardProc looks like:
LRESULT CALLBACK HookLowLevel::KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
c++ winapi boost
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
My problem I think that is due to the fact that I try to bind a class member function (not static) as a callback to the SetWindowsHookEx function. I've tried debugging but I was unable to get any other useful info except the callback binding which I'm not aware of any other way of doing so.
Therefore, at the first call of the GetMessage function I receive the following exception: An unhandled exception was encountered during a user callback. .
My question is, if the cause of the exception is the way I'm binding the HookLowLevel::KeyboardProc function so I can pass it as a callback, what's the right way of doing so? If not, what do you think may be the cause of the exception being thrown?
The function inside which I'm doing the callback binding and where the GetMessage function that throws the exception is found:
void HookLowLevel::attachHook()
{
printf("Hooking the keyboardn");
auto callback = std::bind(&HookLowLevel::KeyboardProc, this);
hook_ = SetWindowsHookEx(WH_KEYBOARD_LL, (HOOKPROC)(&callback), 0, 0);
printf("%Xn", hook_);
MSG msg{ 0 };
try
{
while (GetMessage(&msg, NULL, 0, 0) != 0 && !windowChanged_)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
catch (const std::runtime_error& re)
{
std::cerr << "Runtime error: " << re.what() << std::endl;
}
catch (const std::exception &e)
{
std::cerr << "exception: " << e.what();
}
}
And this is how the definition of the KeyboardProc looks like:
LRESULT CALLBACK HookLowLevel::KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
c++ winapi boost
c++ winapi boost
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
asked Nov 15 '18 at 9:34
Gor BlurGor Blur
33
33
Remove the cast toHOOKPROC, and so your function call becomesSetWindowsHookEx(WH_KEYBOARD_LL, callback, 0, 0);Does this compile? If it does not, thencallbackis not of the correct signature. No amount of casting can change that. The cast toHOOKPROCin your code would merely be a means for you to tell a big fat lie to the compiler. Those lies seldom end well.
– David Heffernan
Nov 15 '18 at 10:05
add a comment |
Remove the cast toHOOKPROC, and so your function call becomesSetWindowsHookEx(WH_KEYBOARD_LL, callback, 0, 0);Does this compile? If it does not, thencallbackis not of the correct signature. No amount of casting can change that. The cast toHOOKPROCin your code would merely be a means for you to tell a big fat lie to the compiler. Those lies seldom end well.
– David Heffernan
Nov 15 '18 at 10:05
Remove the cast to
HOOKPROC, and so your function call becomes SetWindowsHookEx(WH_KEYBOARD_LL, callback, 0, 0); Does this compile? If it does not, then callback is not of the correct signature. No amount of casting can change that. The cast to HOOKPROC in your code would merely be a means for you to tell a big fat lie to the compiler. Those lies seldom end well.– David Heffernan
Nov 15 '18 at 10:05
Remove the cast to
HOOKPROC, and so your function call becomes SetWindowsHookEx(WH_KEYBOARD_LL, callback, 0, 0); Does this compile? If it does not, then callback is not of the correct signature. No amount of casting can change that. The cast to HOOKPROC in your code would merely be a means for you to tell a big fat lie to the compiler. Those lies seldom end well.– David Heffernan
Nov 15 '18 at 10:05
add a comment |
1 Answer
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The Windows API is strictly exposed as a C interface. You cannot pass pointers to non-static class members as callbacks to any Windows API (or function objects as returned by std::bind). The compiler told you about this already, which probably resulted in you silencing the compiler by adding an (invalid) cast.
Remove the cast and the compiler will let you know, whether you passed a function pointer with the correct signature. You can also safely remove your try/catch handlers. The Windows API will not ever throw a C++ exception (see first paragraph).
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
add a comment |
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1 Answer
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1 Answer
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oldest
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The Windows API is strictly exposed as a C interface. You cannot pass pointers to non-static class members as callbacks to any Windows API (or function objects as returned by std::bind). The compiler told you about this already, which probably resulted in you silencing the compiler by adding an (invalid) cast.
Remove the cast and the compiler will let you know, whether you passed a function pointer with the correct signature. You can also safely remove your try/catch handlers. The Windows API will not ever throw a C++ exception (see first paragraph).
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
add a comment |
The Windows API is strictly exposed as a C interface. You cannot pass pointers to non-static class members as callbacks to any Windows API (or function objects as returned by std::bind). The compiler told you about this already, which probably resulted in you silencing the compiler by adding an (invalid) cast.
Remove the cast and the compiler will let you know, whether you passed a function pointer with the correct signature. You can also safely remove your try/catch handlers. The Windows API will not ever throw a C++ exception (see first paragraph).
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
add a comment |
The Windows API is strictly exposed as a C interface. You cannot pass pointers to non-static class members as callbacks to any Windows API (or function objects as returned by std::bind). The compiler told you about this already, which probably resulted in you silencing the compiler by adding an (invalid) cast.
Remove the cast and the compiler will let you know, whether you passed a function pointer with the correct signature. You can also safely remove your try/catch handlers. The Windows API will not ever throw a C++ exception (see first paragraph).
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
The Windows API is strictly exposed as a C interface. You cannot pass pointers to non-static class members as callbacks to any Windows API (or function objects as returned by std::bind). The compiler told you about this already, which probably resulted in you silencing the compiler by adding an (invalid) cast.
Remove the cast and the compiler will let you know, whether you passed a function pointer with the correct signature. You can also safely remove your try/catch handlers. The Windows API will not ever throw a C++ exception (see first paragraph).
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
edited Nov 15 '18 at 10:15
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
answered Nov 15 '18 at 10:05
IInspectableIInspectable
26.2k54396
26.2k54396
add a comment |
add a comment |
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Remove the cast to
HOOKPROC, and so your function call becomesSetWindowsHookEx(WH_KEYBOARD_LL, callback, 0, 0);Does this compile? If it does not, thencallbackis not of the correct signature. No amount of casting can change that. The cast toHOOKPROCin your code would merely be a means for you to tell a big fat lie to the compiler. Those lies seldom end well.– David Heffernan
Nov 15 '18 at 10:05