How to create a Dynamic Library in D? - dll

I want to create a Dynamic library (cross-platform) in D, so I did some Googling. After some time I found this page. I am absolutely stunned by how much complexities there are in writing, compiling and even linking to a DLL. Isn't there a uniform way of creating a shared library like you would in C? (just leave out the main function and pass some flags to the linker)

Well, I decided to spend some time today messing with this and I kinda sorta have something that works, at least if the main program is also written in D (on Linux, I think it will work from C too on Windows. The reason is I didn't link to phobos in the .so in the D one, so it relies upon the exe for those symbols. I think, tbh I don't know exactly what is going on here, maybe it would work better if I used the shared phobos lib too)
Anyway, first, let's throw some code down.
This is testdll.d and it builds our dll
module testdll;
import std.stdio;
extern(C)
export void lol() {
import core.stdc.stdio;
printf("hello from C\n");
writeln("hello!");
}
version(Windows)
extern(Windows) bool DllMain(void* hInstance, uint ulReason, void*) {
import std.c.windows.windows;
import core.sys.windows.dll;
switch (ulReason)
{
default: assert(0);
case DLL_PROCESS_ATTACH:
dll_process_attach( hInstance, true );
break;
case DLL_PROCESS_DETACH:
dll_process_detach( hInstance, true );
break;
case DLL_THREAD_ATTACH:
dll_thread_attach( true, true );
break;
case DLL_THREAD_DETACH:
dll_thread_detach( true, true );
break;
}
return true;
}
You'll notice most that code is the WinMain which just calls druntime functions. I think that main should be available at least as a mixin, or maybe even fully automatic, since it is pure boilerplate.
And the client code:
import core.runtime;
alias extern(C) void function() functype;
version(Posix) {
extern(C) void* dlsym(void*, const char*);
extern(C) void* dlopen(const char*, int);
extern(C) char* dlerror();
pragma(lib, "dl");
} else version(Windows) {
extern(Windows) void* LoadLibraryA(const char* filename);
extern(Windows) void* GetProcAddress(void*, const char*);
}
void main() {
version(Posix) {
auto thing = dlopen("./testdll.so", 2);
if(thing is null) {
import std.conv;
import std.stdio;
writeln(to!string(dlerror()));
return;
}
auto proc = cast(functype) dlsym(thing, "lol");
} else version(Windows) {
auto thing = LoadLibraryA("testdll.dll");
assert(thing !is null);
auto proc = cast(functype) GetProcAddress(thing, "lol");
}
assert(proc !is null);
//import std.stdio; writeln("calling proc");
proc();
}
This has different code for Windows and Linux, though it is pretty similar. The druntime stuff is supposed to start taking care of this soon as we mentioned in the comments.
The compile commands aren't too bad but a little weird. Linux first:
dmd -fPIC -shared testdll.d -defaultlib= # builds the dll
PIC and shared tell it to build the .so. I did the blank defaultlib because without it, loading the dll at runtime failed with "symbol already defined" errors.
Building the client is straightforward:
dmd testdllc.d
Note that there's the pragma(lib) in the file that links with the -ldl option automatically. Run it and get some hello! BTW be sure both are in the same directory since this loads ./ in the loader.
Now, let's build on Windows.
dmd -oftestdll.dll -shared testdll.d testdll.def
Tell it to output our dll, use -shared so it knows, and then the other thing is the def file, like described here http://dlang.org/dll.html/dllmain
These are the contents of that file:
LIBRARY testdll
EXETYPE NT
CODE SHARED EXECUTE
DATA WRITE
EXPORTS
lol
If you don't use the .def file, the dll will build successfully, but the procedure won't be found because it isn't exported. (I think the export keyword in D should be able to do this automatically, bypassing hte .def file, and I believe there's a discussion on doing this, but right now it is required as far as I know.)
And the client is similarly easy:
dmd testdllc.d
Run it and get some hellos, if all goes well.
Now, why did I do the functype alias in the client? Easier than doing the other casting and such, and it makes it nicely extern(C).
Why is the lol function extern(C) in the first place? Just so it has an easier name to use in GetProcAddress/dlsym. Could have also pragma(mangle) or did .mangleof with an import thing. All kinds of options there, fairly straightforward, I just wanted to keep it simple to make the test easier to focus on. "lol" is a simpler name than "_D7testdll3lolFZv" or whatever the mangled name would be.... (OMG I mangled it correctly by hand! Sometimes I think I write too much D lol) and yeah that works too it is just harder to do by eyeball. Note: on Windows, the .def file might have to leave off the leading underscore if you do it that way.
anyway, yeah, this made a working dll/so for me and a program to load and use it successfully. Not as pretty as it could/should be, but it works. For me at least.

Related

import cycle in golang with test packages

I am trying to refactor some test code and in two packages I need to do the same thing (connect to a DB). I am getting an import cycle. I get why I can't do it, but am wondering what the best way around it is.
Some specifics, I have three packages: testutils, client, engine.
In engine I define an interface & implementation (both exported).
package engine
type interface QueryEngine {
// ...
}
type struct MagicEngine {
// ...
}
And then in the testutils package I will create a MagicEngine and try and return it.
package testutils
func CreateAndConnect() (*engine.MagicEngine, error) {
// ....
}
Now in the test code (using a TestMain) I need to do something like
package engine
func TestMain(m *testing.M) {
e, err := testutils.CreateAndConnect()
// ....
os.Exit(m.Run())
}
This is of course a cycle. I want to do this so that I can in the client package also use this testutils.CreateAndConnect() method. I don't want to repeat the code in both packages. I don't want it in the main code of the engine package, it is very specific to the tests.
I tried adding it as an exported method on the engine test class (engine/engine_test.go) and using it in the client/client_test.go. No dice. :/
I feel I have done this in other languages, but could be crazy. What is the best way to structure this code for reusability?
You could use black-box style testing because the components of engine are exported. Change your tests to be in package engine_test:
package engine_test
import "engine"
import "testutils"
func TestMain(m *testing.M) {
e, err := testutils.CreateAndConnect()
// ....
os.Exit(m.Run())
}

Exporting TASKLET in kernel module?

I got two kernel modules which both exports some symbols using EXPORT_SYMBOL().
One of them exports basic function (sv1<-sv2) and it works but I got problem with the other one (sv1->sv2).
What I want is to export TASKLET. I read somewhere that is possibile and there is no proscription of doing this. Module nr 1 (called sv1) consists of BH Function and declaration of tasklet:
struct tasklet_struct sv_takslet;
EXPORT_SYMBOL(sv_takslet);
void sv_tasklet_function( unsigned long data )
{
printk( "%s\n", (char *)data );
return;
}
static int __init sv_publisher_init(void)
{
...
tasklet_init(&sv_takslet, &sv_tasklet_function,&sv_tasklet_data);
...
}
In second module there is global reference and task_schedule() function used at initialization of the module nr 2 (called sv2):
extern struct tasklet_struct sv_takslet;
...
tasklet_schedule(&sv_takslet);
The problem is when I got:
tasklet_schedule(&sv_takslet);
in my code I do not see my two modules on list (modprobe -l), but when I comment this line on sv2- they magically appear.
What could be a cause of that behavior? Is this initialization is correct?
EDIT
The cause of this problem is that module sv2 is loading before sv1 and has no knowledge about the tasklet (line: extern struct tasklet_struct sv_takslet). When I change destination that sv2 exports TASKLET to sv1 the problem is gone.
But now I am facing with that both modules have to export symbols to each other. I have no idea how to solve this problem...
Both *.c files are in the same directory and my Makefile has following line:
obj-m += sv_publisher.o zsv_core.o
Does anybody have some tips how to go about it?

In SourceMod, how do I check if a plugin exists?

In SourceMod, how do I check if a plugin exists? I tried the GetFeatureStatus method, but it doesn't work. Any ideas?
If a plugin has registered itself as a Library, you can check if it exists using the LibraryExists command on the name it registered. Traditionally, this name is in all lowercase, but some plugins/extensions use mixed-case, such as SteamTools (which uses "SteamTools").
Having said that, it's generally better to cache whether a library exists instead of constantly calling this command... but then a library can be unloaded or loaded on your without your knowledge. There are functions to catch that.
So, the best way is generally to do something like this (using the NativeVotes plugin as an example).
#undef REQUIRE_PLUGIN
#include <nativevotes>
//global variable
new bool:g_bNativeVotes = false;
public OnAllPluginsLoaded()
{
g_bNativeVotes = LibraryExists("nativevotes");
}
public OnLibraryAdded(const String:name[])
{
if (StrEqual(name, "nativevotes"))
{
g_bNativeVotes = true;
}
}
public OnLibraryRemoved(const String:name[])
{
if (StrEqual(name, "nativevotes"))
{
g_bNativeVotes = false;
}
}
If a plugin isn't registered as a library, you can use GetFeatureStatus to check for a particular native. The catch is in realizing that this function doesn't return a bool, but rather a FeatureStatus_ value.
For instance, here's how I'd check for a (in development) feature for the same plugin as mentioned above:
if (GetFeatureStatus(FeatureType_Native, "NativeVotes_IsVoteCommandRegistered") == FeatureStatus_Available)
{
// Do something with vote commands.
}

Registering for Display Reconfiguration Callbacks

I'm putting together a Mac OS X Application and I'm trying to register to receive Display Reconfiguration notices, but I'm very lost right now. I've been reading Apple's documentation and some forums posts, etc., but everything seems to assume a better knowledge of things than I apparently possess. I understand that I have to request the callback inside a run loop for it to work properly. I don't know how to set up a basic run loop for it, though. I also feel like the example Apple has in their documentation is missing stuff they are expecting me to already know. To display my ignorance here is what I feel like things should look like.
NSRunLoop *rLoop = [NSRunLoop currentRunLoop];
codeToStartRunLoop
void MyDisplayReconfigurationCallBack (
CGDirectDisplayID display,
CGDisplayChangeSummaryFlags flags,
void *userInfo);
{
if (flags & kCGDisplayAddFlag) {
NSLog (#"Display Added");
}
else if (kCGDisplayRemoveFlag) {
NSLog (#"Display Removed");
}
}
CGDisplayRegisterReconfigurationCallback(MyDisplayReconfigurationCallBack, NULL);
The actual code I got was from Apple's Example, but it tells me that flags is an undeclared identifier at this point and won't compile. Not that it would work right since I don't have it in a run loop. I was hoping to find a tutorial somewhere that explains registering for system callback in a run loop but have not been successful. If anyone could point me in the right direction I'd super appreciate it.
(I'm sure that you'll be able to tell from my question that I'm very green. I taught myself Objective-C out of a book as my first programming language. I skipped C, so every once in a while I hit a snag somewhere that I can't figure out.)
If you're writing a Mac OS X application, the AppKit has already set up a run loop for you, so you don't need to worry about that part. You really only need to create your own run loop in Cocoa when you are also creating your own thread.
For the "undeclared identifier" part, it looks like it's due to a typo/syntax mistake:
void MyDisplayReconfigurationCallBack (CGDirectDisplayID display,
CGDisplayChangeSummaryFlags flags,
void *userInfo);
// Semicolon makes this an invalid function definition^^
{
// This is an anonymous block,* and flags wasn't declared in it
if (flags & kCGDisplayAddFlag) {
// etc.
}
Also, unlike some other languages, you can't declare or define functions inside of other functions, methods, or blocks* -- they have to be at the top level of the file. You can't put this in the same place where you call CGDisplayRegisterReconfigurationCallback.
Just as an sample (I have no idea what the rest of your code really looks like):
// MyClassThatIsInterestedInDisplayConfiguration.m
#import "MyClassThatIsInterestedInDisplayConfiguration.h"
// Define callback function at top level of file
void MyDisplayReconfigurationCallBack (
CGDirectDisplayID display,
CGDisplayChangeSummaryFlags flags,
void *userInfo)
{
if (flags & kCGDisplayAddFlag) {
NSLog (#"Display Added");
}
else if (kCGDisplayRemoveFlag) {
NSLog (#"Display Removed");
}
}
#implementation MyClassThatIsInterestedInDisplayConfiguration
- (void) comeOnBabyAndDoTheRegistrationWithMe {
// Register callback function inside a method
CGDisplayRegisterReconfigurationCallback(MyDisplayReconfigurationCallBack,
NULL);
}
#end
*The basic C curly-brace-delimited thing, not the new cool Obj-C ad hoc function thing.

How to use System::Threading::Interlocked::Increment on a static variable from C++/CLI?

I would like to keep a static counter in a garbage collected class and increment it using Interlocked::Increment. What's the C++/CLI syntax to do this?
I've been trying variations on the following, but no luck so far:
ref class Foo
{
static __int64 _counter;
__int64 Next()
{
return System::Threading::Interlocked::Increment( &_counter );
}
};
You need to use a tracking reference to your _int64 value, using the % tracking reference notation:
ref class Bar
{
static __int64 _counter;
__int64 Next()
{
__int64 %trackRefCounter = _counter;
return System::Threading::Interlocked::Increment(trackRefCounter);
}
};
Just remove the address-of operator:
return System::Threading::Interlocked::Increment( _counter );
In C++/CLI, like C++, there is no special notation for passing by reference.
or you could use the native function, InterlockedIncrement64 (#include <windows.h>)
return ::InterlockedIncrement64(&_counter);
The suggestion to use the native functions/macros (i.e. InterlockedExchangePointer, etc... plus a lot of cool ones I didn't know about such as InterlockedXor64) is severely hampered by the fact that doing so can cause an intrinsic (at least with the default compiler settings) to be dropped into your managed C++/CLI function. When this happens, your whole function will be compiled as native.
And the managed versions of Interlocked::* are also nice because you don't have to pin_ptr if the target is in a GC object. However, as noted on this page, it can be a real pain to find the right incantations for getting it to work, especially when you want to swap, (i.e) native pointers themselves. Here's how:
int i1 = 1, i2 = 2;
int *pi1 = &i1, *pi2 = &i2, *pi3;
pi3 = (int*)Interlocked::Exchange((IntPtr%)pi1, IntPtr(pi2)).ToPointer();
I verified that this does work properly, despite the suspiciously unnerving lack of address-taking (&) on the pi1 pointer. But it makes sense, when you think about it because if the target is moving about in a GC host, you wouldn't want to do the usual ** thing by grabbing the & (native) address of the pointer itself.