Use CGO in your .go file, and then there, or in an adjacent C file,
actually do write a DllMain function;
https://learn.microsoft.com/en-us/windows/win32/dlls/dllmain
When fdwReason == DLL_PROCESS_ATTACH, then you know this is the first load
of the DLL
into this process. I think your subject line acknowledges that you known
this.
Note that the APIENTRY annotation on the DllMain is required, in order to
get the
right calling convention.
Be aware that the go runtime has a major problem when used inside a DLL: it
provides no way to shut itself down. This means that you can never unload
a DLL that you have loaded, even though Windows processes routinely do
unload DLLs.
On XP or later you can use GetModuleHandleEx with the
GET_MODULE_HANDLE_EX_FLAG_PIN flag to prevent unloading of the DLL.
This means that your process won't crash on unload, but also that the
DLL will not actually be unloaded. In order to update the DLL, you must
kill the
process.
On Sunday, November 10, 2024 at 1:54:16 PM UTC rudeus greyrat wrote:
> I am trying to write DLL in go. I want it to execute some stuff when the
> DLL is attached to a process.
>
> I thought init() will be the equivalent of onattach but It seems I am
> wrong.
>
> I created this as a proof of concept:
> ```
> package main
>
> import "C"
> import (
> "syscall"
>
> "golang.org/x/sys/windows"
> )
>
> //export RunMe
> func RunMe() {
>
> windows.MessageBox(windows.HWND(0),
> syscall.StringToUTF16Ptr("RunMe"), syscall.StringToUTF16Ptr("RunMe"),
> windows.MB_OK)
> }
>
> func init() {
> windows.MessageBox(windows.HWND(0), syscall.StringToUTF16Ptr("DLL
> Loaded"), syscall.StringToUTF16Ptr("DLL Load"), windows.MB_OK)
> }
>
> func main() {}
> ```
>
> I compile on Linux with:
> ```
> GOOS=windows GOARCH=amd64 CGO_ENABLED=1 CC=x86_64-w64-mingw32-gcc go build
> -a -o ~/Desktop/dropamd64.dll -buildmode=c-shared cmd/dll64bit/main.go
> ```
>
> I transfer on my Windows machine then here is the amazing result:
> *rundll32.exe Z:\dropamd64.dll -----> Nothing happens*
> *rundll32.exe Z:\dropamd64.dll,RunMe ------> Runs RunMe() and init() and
> I get 2 MessageBox*
>
> My question is, how to get a DLL that runs stuff only when process is
> attached ?
>
> There not a lot of official Golang doc about DLL (some few people write
> here and there some tutorials that are not always right and correct ...) So
> if you have some trustworthy doc please share.
>
>
>
>
>
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