request for member in something not a structure or union
Author
I am working with windows hook's, and previously (working on a different project) ran into this issue and couldnt figure out a resolution, but this time i really need to know.
in the following callback function:
LRESULT CALLBACK LowLevelKeyboardProc(int code, WPARAM wParam, LPARAM lParam)
I have the following statement:
DWORD laa = *lParam.vkCode;
Microsoft's comment on the lParam parameter:
lParam
[in] Pointer to a KBDLLHOOKSTRUCT structure.
and the structure is like this:
typedef struct {
DWORD vkCode;
DWORD scanCode;
DWORD flags;
DWORD time;
ULONG_PTR dwExtraInfo;
} KBDLLHOOKSTRUCT, *PKBDLLHOOKSTRUCT;
but, it get the error "request for member `vkCode' in something not a structure or union"
I tried just declaring one of these structures on its own to test the idea, but still the same error. Why cant i access struct properties?
I would appreciate any input on this. Thans :) (if not for replying, then for reading this much)
Did you try (*lParam).vkCode? or lParam->vkCode?
Maybe an explicit cast is needed here
KBDLLHOOKSTRUCT *kbs = static_cast<KBDLLHOOKSTRUCT*>(lParam);
kbs->vkCode...
Maybe an explicit cast is needed here
KBDLLHOOKSTRUCT *kbs = static_cast<KBDLLHOOKSTRUCT*>(lParam);
kbs->vkCode...
Author
pulpfist, i'm using C ... and the following code doesnt work either:
KBDLLHOOKSTRUCT* laa = (KBDLLHOOKSTRUCT*)lParam;
DWORD dee = *laa.vkCode;
Am i correct in thinking that there is something very strange going on here? I've never had any troubles like this before :(
KBDLLHOOKSTRUCT* laa = (KBDLLHOOKSTRUCT*)lParam;
DWORD dee = *laa.vkCode;
Am i correct in thinking that there is something very strange going on here? I've never had any troubles like this before :(
Quote:
pulpfist, i'm using C ... and the following code doesnt work either:
KBDLLHOOKSTRUCT* laa = (KBDLLHOOKSTRUCT*)lParam;
DWORD dee = *laa.vkCode;
Am i correct in thinking that there is something very strange going on here? I've never had any troubles like this before :(
DWORD dee = laa->vkCode;
or
DWORD dee = (*laa).vkCode;
Did you try pulpfist's first two suggestions, (*lParam).vkCode and lParam->vkCode? In your latter example it would be DWORD dee = (*laa).vkCode.
Author
Quote:Original post by jyk
Did you try pulpfist's first two suggestions, (*lParam).vkCode and lParam->vkCode? In your latter example it would be DWORD dee = (*laa).vkCode.
To be honest, i didnt try the -> one because i thought it was c++ specific, but to be sure just then i tried it and it works 100% :D
I thought "laa->vkCode" was the alternative to "*laa.vkCode" though ?
Thanks for the help you guys, i really appreciate it :)
Quote:I thought "laa->vkCode" was the alternative to "*laa.vkCode" though ?It is, but unless you clarify using parentheses, the compiler may have trouble resolving the latter. If laa is a pointer (as in your case), you want (*laa).vkCode; if laa is an object and vkCode is a pointer that you want to dereference, you want *(laa.vkCode); and if they're both pointers you'd need something like *((*laa).vkCode). Using -> syntax helps to avoid some of these ambiguities.
basically by typeing
*lparam.vkcode is the same to the compiler as *(lparam.vkcode)
use the -> for simplicity sake
you was trying to get a value from a memory location stored at the long interpreted as a bad address, thats what that error means
*lparam.vkcode is the same to the compiler as *(lparam.vkcode)
use the -> for simplicity sake
you was trying to get a value from a memory location stored at the long interpreted as a bad address, thats what that error means
-> is from like original c standard isnt it? i know even the oldest tutorials i use have it
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