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Greg Bullock · Guest

I've got two applications. The second one is supposed to call a function in
the first one. I must not be doing this correctly, as the line calling the
function gives an access violation. I don't even know how to debug this
sort of thing. Here's what I've got.

AppOne exports a function declared as follows:

TMyStruct __stdcall __declspec(dllimport) GetMyStruct(
const char *StrA,
const char *StrB,
const SYSTEMTIME& DateTime);

AppTwo attempts to call this function using code something like the
following:

typedef TMyStruct __stdcall (*pGetMyStruct)(const char *StrA, const char
*StrB, const SYSTEMTIME& DateTime);

void FuncA()
{
SYSTEMTIME SystemTime;
::GetSystemTime(&SystemTime);

HMODULE AppOneModule = LoadLibrary("AppOne.Exe");
pGetMyStruct GetMyStructFunc =
reinterpret_cast<pGetMyStruct>(GetProcAddress(AppOneModule,
"@GetMyStruct$qqspxct1rx11_SYSTEMTIME"));
if (!GetMyStructFunc)
return;

// --- The next line produces an Access Violation ---
TMyStruct MyStruct = (GetMyStructFunc)(
"this is string 1",
"this is string 2", SystemTime);

...
}

The line marked above produces the following Access Violation:
Project AppTwo.exe raised exception class EAccessViolation with message
'Access violation at address 01171177 in module AppOne.Exe'. Read of address
0085E880. Process stopped. Use Step or Run to continue.

In the definition of GetMyStruct(...), the first executable line is

::MessageBox(0, "Arrived in GetMyStruct", "Made it!", MB_OK);

but no such message is displayed before the access violation occurs.

Any help most appreciated.

Regards.
Greg

Remy Lebeau (TeamB) · Guest

"Greg Bullock" <greg dot bullock at atk dot com> wrote

Greg Bullock · Guest

Thanks very much, Gambit.

I'll use Automation or RPC, as you recommend.

The exported function uses some objects with C++Builder language extensions
(e.g., "__published") which are off-limits to the other application. These
objects are also used elsewhere in the exporting application, so I felt the
best way to let both applications link to the same function is to export the
critical function from that application.

Thanks for pointing me to Automation and RPC.

Regards.
Greg

"Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote