Henryk Birecki schrieb:
I need to use a dll that is dynamically linked to a program (sometimes
it exists, and sometimes not). The dll exports some functions and some
data (integers). I can easily get at the functions with
GetProcAddress, but how do I get at the data? Building the program
gives me unresolved external references errors. If DLL is mine, then I
can add functions that will pass appropriate data, but what if I
cannot do that?
What am I missing?
GetProcAddress() does not know about functions and variables. It just
reads the address of exported items from the DLL's export table.
Therefore, GetProcAddress can also be used to get the address of
exported variables.
I just tried this and it works:
vartest.cpp:
extern "C" typedef __declspec(dllimport) void (*setvar_t)(int);
int _tmain(int argc, _TCHAR* argv[])
{
HMODULE lib = ::LoadLibrary(_T("varlib.dll"));
setvar_t setvar = (setvar_t)::GetProcAddress(lib, "setvar");
int* val = (int*)::GetProcAddress(lib, "value");
setvar(34);
_tprintf(_T("value is: %d\n"), *val); // prints 34
::FreeLibrary(lib);
return 0;
}
varlib.cpp:
[DllMain omited]
extern "C" {
__declspec(dllexport) int value;
__declspec(dllexport) void setvar(int val)
{
value = val;
}
}
Norbert
Right. But you are not accessing an exported variable. You have
function. I can do that as long as it is my dll. But not otherwise.