Calling an external function with GetProcAddress crashes the app - c++

Question

I've been trying to call an external function with the GetProcAddress function but everytime i call the function it crashes the console, ive been looking but in every post i get the same final solution but when i try it in my DLL it crashes the app.
Here's the code:
#include <Windows.h>
#include <vector>
#include "SDK\plugin.h"
typedef void (*logprintf_t)(char* format, ...);
logprintf_t logprintf;
// static void* m_AMXExports[44];
typedef bool (PLUGIN_CALL *ServerPluginLoad_t)(void **data);
typedef void (PLUGIN_CALL *ServerPluginUnload_t)();
typedef unsigned int (PLUGIN_CALL *ServerPluginSupports_t)();
typedef void (PLUGIN_CALL *ServerPluginProcessTick_t)();
typedef int (PLUGIN_CALL *ServerPluginAmxLoad_t)(AMX *amx);
typedef int (PLUGIN_CALL *ServerPluginAmxUnload_t)(AMX *amx);
struct Plugins
{
void* AppData[256];
SUPPORTS_FLAGS FlagSupport;
HMODULE Module;
ServerPluginLoad_t LOAD;
ServerPluginUnload_t UNLOAD;
ServerPluginSupports_t SUPPORTS;
ServerPluginProcessTick_t PROCESSTICK;
// AMX Plugin Interface
ServerPluginAmxLoad_t AMXLOAD;
ServerPluginAmxUnload_t AMXUNLOAD;
};
Plugins* ServerPlugins;
void **ppPluginData ;
extern void *pAMXFunctions;
//native LoadLibrary(libraryname[]);
static cell AMX_NATIVE_CALL my_LoadLibrary(AMX* amx, cell* params)
{
bool validfunc = false;
char *path;
amx_StrParam(amx, params[1], path);
logprintf("Loading plugin %s", path);
ServerPlugins = new Plugins();
ServerPlugins->Module = LoadLibraryA(path);
if (ServerPlugins->Module == NULL)
{
delete ServerPlugins;
logprintf("Failed loading plugin %s (Error: %d)", path, GetLastError());
return 0;
}
logprintf("NULL");
ServerPlugins->LOAD = (ServerPluginLoad_t)GetProcAddress(ServerPlugins->Module, "Load");
ServerPlugins->UNLOAD = (ServerPluginUnload_t)GetProcAddress(ServerPlugins->Module, "Unload");
ServerPlugins->SUPPORTS = (ServerPluginSupports_t)GetProcAddress(ServerPlugins->Module, "Supports");
if (ServerPlugins->LOAD == NULL || ServerPlugins->SUPPORTS == NULL || ServerPlugins->UNLOAD == NULL)
{
logprintf(" Plugin doesnt conform to architecture");
FreeLibrary(ServerPlugins->Module);
delete ServerPlugins;
return false;
}
logprintf("NULL 1");
ServerPlugins->FlagSupport = (SUPPORTS_FLAGS)ServerPlugins->SUPPORTS();
if ((ServerPlugins->FlagSupport & SUPPORTS_VERSION_MASK) > SUPPORTS_VERSION)
{
logprintf("Unsupported Version; unloading.");
FreeLibrary(ServerPlugins->Module);
delete ServerPlugins;
return false;
}
logprintf("NULL 2");
if ((ServerPlugins->FlagSupport & SUPPORTS_AMX_NATIVES) > SUPPORTS_VERSION)
{
ServerPlugins->AMXLOAD = (ServerPluginAmxLoad_t)GetProcAddress(ServerPlugins->Module, "AmxLoad");
ServerPlugins->AMXUNLOAD = (ServerPluginAmxUnload_t)GetProcAddress(ServerPlugins->Module, "AmxUnload");
}
else
{
ServerPlugins->AMXLOAD = NULL;
ServerPlugins->AMXUNLOAD = NULL;
logprintf("Any Abstract Machine has been loaded");
}
logprintf("NULL 3");
if ((ServerPlugins->FlagSupport & SUPPORTS_PROCESS_TICK) != 0)
{
ServerPlugins->PROCESSTICK = (ServerPluginProcessTick_t)GetProcAddress(ServerPlugins->Module, "ProcessTick");
}
else
{
ServerPlugins->PROCESSTICK = NULL;
}
logprintf("NULL 4"); //debugging
ServerPlugins->AppData[PLUGIN_DATA_AMX_EXPORTS] = pAMXFunctions;
ServerPlugins->AppData[PLUGIN_DATA_LOGPRINTF] = &logprintf;
if (!(ServerPlugins->LOAD)(ServerPlugins->AppData)) //i didnt put it as &ServerPlugins->AppData because it causes an error
{
logprintf("Initialized failed loading plugin %s", path);
FreeLibrary(ServerPlugins->Module);
logprintf("NULL 5");
delete ServerPlugins;
return false;
}
logprintf("Plugin %s loaded", path);
return true;
}
//native UnloadLibrary(libraryname[]);
static cell AMX_NATIVE_CALL my_UnloadLibrary(AMX*amx, cell*params)
{
char *path;
amx_StrParam(amx, params[1], path);
ServerPlugins->Module = GetModuleHandle((LPCTSTR)path);
if (ServerPlugins->Module != NULL)
{
ServerPlugins->UNLOAD = (ServerPluginUnload_t)GetProcAddress(ServerPlugins->Module, "Unload");
if (ServerPlugins->UNLOAD != NULL)
{
ServerPlugins->UNLOAD();
FreeLibrary(GetModuleHandleA(path));
logprintf("Library %s has been unloaded correctly", path);
return 1;
}
else
{
logprintf("Unloading library %s failed (Error: %d)", GetLastError());
return 0;
}
}
return 1;
}
PLUGIN_EXPORT bool PLUGIN_CALL Load(void **ppData)
{
pAMXFunctions = ppData[PLUGIN_DATA_AMX_EXPORTS];
logprintf = (logprintf_t)ppData[PLUGIN_DATA_LOGPRINTF];
return 1;
}
PLUGIN_EXPORT void PLUGIN_CALL Unload()
{
}
PLUGIN_EXPORT unsigned int PLUGIN_CALL Supports()
{
return SUPPORTS_VERSION | SUPPORTS_AMX_NATIVES;
}
AMX_NATIVE_INFO projectNatives[] =
{
{ "LoadLibrary", my_LoadLibrary },
{ "UnloadLibrary", my_UnloadLibrary }
};
PLUGIN_EXPORT int PLUGIN_CALL AmxLoad(AMX *amx)
{
return amx_Register(amx, projectNatives, -1);
}
PLUGIN_EXPORT int PLUGIN_CALL AmxUnload(AMX *amx)
{
return AMX_ERR_NONE;
}

Answer 1

You have a memory leak in convertCharArrayToLPCWSTR(). You are never freeing the wchar_t* that you allocate. The convertCharArrayToLPCWSTR() function itself is not needed, you can simply pass the char* path as-is to LoadLibraryA() instead:
char *path;
amx_StrParam(amx, params[1], path);
...
ServerPlugins->Module = LoadLibraryA(path);
You are not checking if ServerPlugins->UNLOAD is successfully loaded by GetProcAddress("Unload") or not.
You are using GetProcAddress("Load") for both ServerPlugins->LOAD and ServerPlugins->AMXLOAD, and GetProcAddress("Unload") for both ServerPlugins->UNLOAD and ServerPlugins->AMXUNLOAD. That is very fishy to me. Does the DLL really use the same exports for AMX and non-AMX entry points? If so, that is very bad design, considering that ServerPluginLoad_t has a very different signature than ServerPluginAmxLoad_t, and the same for ServerPlugin(Amx)Unload_t. That is a corrupted call stack waiting to happen. It would be much safer to have the DLL export separate AmxLoad() and AmxUnload() functions instead.
For that matter, the SUPPORTS_AMX_NATIVES and SUPPORTS_PROCESS_TICK flags are redundant, since GetProcAddress() would tell you if those exports are available or not.
As for the crash when calling ServerPlugins->LOAD, I do not see you initializing ppData with any data before passing it to Load(). Certainly not the PLUGIN_DATA_AMX_EXPORTS and PLUGIN_DATA_LOGPRINTF slots, at least:
ppData[PLUGIN_DATA_AMX_EXPORTS] = pAMXFunctions;
ppData[PLUGIN_DATA_LOGPRINTF] = &logprintf;
if (!(ServerPlugins->LOAD)(ppData))
So even if the call to Load() itself did not crash, the DLL would still likely crash at a later time when it tries to use its local pAMXFunctions and logprintf pointers that were assigned in Load().
For that matter, why are you passing things like that as a void* array instead of a struct? That would have been much safer, eg:
struct PluginInitData
{
void* pAMXFunctions;
logprintf_t logprintf;
...
};
typedef bool (__stdcall *ServerPluginLoad_t)(PluginInitData* data);
PluginInitData pInitData;
pInitData.pAMXFunctions = pAMXFunctions;
pInitData.logprintf = &logprintf;
...
if (!(ServerPlugins->LOAD)(&pInitData))
extern "C" bool __stdcall Load(PluginInitData* data)
{
pAMXFunctions = data->pAMXFunctions;
logprintf = data->logprintf;
...
return true;
}
Update: you have fixed most of the issues I mentioned, but now I see that your my_UnloadLibrary() function is implemented wrong. DO NOT call GetModuleHandle() or GetProcAddress() at all, use the existing Module and UNLOAD pointers that were initialized earlier in my_LoadLibrary().
static cell AMX_NATIVE_CALL my_LoadLibrary(AMX* amx, cell* params)
{
char *path;
amx_StrParam(amx, params[1], path);
...
ServerPlugins->Path = path;
...
}
static cell AMX_NATIVE_CALL my_UnloadLibrary(AMX*amx, cell*params)
{
if (ServerPlugins)
{
if (ServerPlugins->UNLOAD != NULL)
ServerPlugins->UNLOAD();
if (ServerPlugins->Module != NULL)
{
FreeLibrary(ServerPlugins->Module);
ServerPlugins->Module = NULL;
}
logprintf("Library %s has been unloaded", ServerPlugins->Path);
delete ServerPlugins;
ServerPlugins = NULL;
}
return 1;
}
If you are still having problems with Load() crashing, then you are just going to have to use your compiler's debugger to find out what is actually happening at run-time. The code shown so far should not be crashing, so either you have a calling convention mismatch, or a data alignment mismatch, or corrupted memory, or something like that. We can't run you debugger for you.