[ajr1234]

I made my own extension but when I load it, the server crashes with a segmentation fault. What is that? Thanks for your help!

[rhelgeby]

I'll let others explain the technical part, but it's obviously a error related to memory/pointers.

I'm not a C++ programmer, but you should check that your pointers/handles/etc. are valid. Maybe it's a simple typo somewhere.

Getting the stack trace would be the first step to figure out where this happened.

[RedSword]

http://en.wikipedia.org/wiki/Segmentation_fault

A segmentation fault can happens when you're trying to read/write (generally more write) memory you're not suposed to be able to. It's kinda "memory access violation" in Windows.

This can happen when, let's say for example, you're getting a pointer value and modify it (so you get out of bound of your program's memory range) and poof ! Segfault.

Hope that makes thing clearer =x

[ajr1234]

Thank you all for your help. Can this also happen because of a detoured function? I found a function I wanted to block in server.so with Ida, and then I used CDetour and a detour template (found in an example somewhere) and blocked the function that way. Or is that the hard way to block a function?

[asherkin]

You are probably using CDetour incorrectly, could you paste your code and the prototype of the function you are trying to detour?

[ajr1234]

At first, I couldn't even get it to compile, but with help from another coder, I ended up with the following code This is the function I'm trying to detour:

namespace Detours {

class CBasePropDoor;

typedef bool (CBasePropDoor::*DoorCanOpenFunc)();

class CBasePropDoor : public DetourTemplate<DoorCanOpenFunc, CBasePropDoor>
{
private: //note: implementation of DetourTemplate abstracts

	bool DoorCanOpen();

	// get the signature name from the game conf
	virtual const char *GetSignatureName()
	{
		return "CBasePropDoor_DoorCanOpen";
	}

	//notify our patch system which function should be used as the detour
	virtual DoorCanOpenFunc GetDetour()
	{
		return &CBasePropDoor::DoorCanOpen;
	}
};

}

extension.cpp:

Sample g_Sample;		/**< Global singleton for extension's main interface */

SMEXT_LINK(&g_Sample);

IForward *g_pFwdDoorCanOpen = NULL;
PatchManager g_PatchManager;
IGameConfig *g_pGameConf = NULL;

bool Sample::SDK_OnLoad(char *error, size_t maxlength, bool late)
{
    char conf_error[250];
    gameconfs->LoadGameConfigFile(GAMECONFIG_FILE, &g_pGameConf, conf_error, sizeof(conf_error));
    g_pFwdDoorCanOpen = forwards->CreateForward("L4D_DoorCanOpen", ET_Event, 2, /*types*/NULL, Param_Array, Param_Array);
}

void Sample::SDK_OnAllLoaded()
{
	g_PatchManager.Register(new AutoPatch<Detours::CBasePropDoor>());
}

void Sample::SDK_OnUnload()
{
    g_PatchManager.UnregisterAll();
	forwards->ReleaseForward(g_pFwdDoorCanOpen);
}

namespace Detours
{
        int iDoor = 0;

	bool CBasePropDoor::DoorCanOpen()
	{
		cell_t result = Pl_Continue;

                if (iDoor != 0)
                    return false;

                iDoor++;

                return true;
	}
}

And the gamedata:

"Games"
{
	"left4dead2"
	{
		"Offsets"
		{
			/* Offset into CDirectorMusicBanks::OnRoundStart */
			"TheDirector"
			{
				"windows"	"8"
			}
		}
		
		"Signatures"
		{
			"CBasePropDoor_DoorCanOpen"
			{
					"library"    "server"
					"linux"  "@_ZN13CBasePropDoor11DoorCanOpenEv"
			}

			/* Find the Director/ZombieManager singleton classes */
			
			"TheDirector"
			{
				"library"	"server"
				"linux"	"@TheDirector"
			}
		}
	}
}

As you can see, I clearly don't know what I'm doing.

[asherkin]

That template system looks extremely convoluted.

Try just using CDetour as-is, my ZombieFix extension (linked in my sig) is a simple example of just blocking a function.

[ajr1234]

Awesome That's much more clear than what I was trying to do!

Can you explain the arguments? I don't know what to put in because I don't know what the arguments mean. -_-

DETOUR_DECL_MEMBER2(DoorCanOpen, void, bool, door, bool, door)

Edit: nvm, since the function I was trying to detour had no arguments and just a return type of bool, I used DETOUR_DECL_MEMBER0. I took your Zombie Fix code and changed it slightly so it would compile. It loads in SM, no problems. But it does nothing. It doesn't report anything to the server or anything -_- Is there PrintToChatAll() or something similar via an extension?

	detourDoorCanOpen = DETOUR_CREATE_MEMBER(DoorCanOpen, "DoorCanOpen");

	if (detourDoorCanOpen != NULL)
	{
		detourDoorCanOpen->EnableDetour();
		snprintf(error, maxlength, "Detoured!!!");
	}
	else
	{
	    snprintf(error, maxlength, "[Open Door] COULD NOT DETOUR!!!");
		return false;
	}

	snprintf(error, maxlength, "Extension loaded!");

	return true;

[Sweet Blasphemy]

You should use

g_pSM->LogMessage(myself, "blahblah");

to log messages. The error argument is only used when you return false, I presume.

[ajr1234]

I see, thanks. Last question: is there a way to print to the chat box, like in plugins where you can just use PrintToChatAll() and have a chat message sent. ie. "[EXT] Door cannot be opened!" in the chat box?