You can not directly call a C function pointer from Go. You will need a CGO
wrapper that calls it and them you call that wrapper from Go.
-Bruno
On Thu, May 15, 2025, 5:20 AM rudeus greyrat <rudeusquagmir...@gmail.com>
wrote:
> Hello,
>
> Thanks for your answer.
>
> Three points to note:
>
> - I never asked how to create an so, I already have a given so :/
> - No need to provide the code because the issue is simple to describe:
> I have an address of a function in a Go variable, how to call it ?
> - AI is garbage (even though I use it)
>
> I thought about using assembly with a call instruction but I hoped someone
> knowledgable would tell me there is a built in Go function for that.
>
> Regards,
> Rudeus
>
>
>
> Le jeudi 15 mai 2025 à 02:46:18 UTC+2, Kurtis Rader a écrit :
>
>> On Wed, May 14, 2025 at 4:17 PM rudeus greyrat <rudeusqu...@gmail.com>
>> wrote:
>>
>>> I am still a beginner in Linux internals so please bear with me.
>>>
>>> I have a ".so" that export "helloworld" function.
>>>
>>> I load the ".so" using CGO by:
>>>
>>> 1. Creating a file descriptor
>>> 2. using ```write``` to write the so to it
>>>
>>> A shared library (".so" file) has a complex structure. You normally
>> create one using a compiler and related tools. For example, the Go compiler
>> can create a .so file from Go source code using a command like
>>
>> go build -buildmode=c-shared -o mylib.so
>>
>> It seems unlikely you are creating a valid .so file by opening an empty
>> file and writing to it unless you are simply copying one .so file to
>> another file.
>>
>>>
>>> 1. Get a handle using ```dlopen```
>>> 2. Get the address of ```helloworld``` symbol using ```dlsym```
>>>
>>> The address of "helloworld" is saved in a go variable called
>>> ```address```
>>>
>>> How to call ```address``` ?
>>>
>>> On windows I am able to call address using ```syscall.SyscallN```. On
>>> Linux I tried with
>>> ```
>>> r1, r2, err := syscall.Syscall(address, 0, 0, 0)
>>> ```
>>>
>>> And I get "function not implemented" error.
>>>
>>
>> I can't speak to Windows but on Unix like operating systems, such as
>> Linux, a function in a shared library is a user space function, not a
>> kernel entry point. A syscall is the way you call OS kernel functions, not
>> user space functions. I wouldn't expect syscall.Syscall() to work on
>> Windows when passed the address of a function in a DLL. Did you actually
>> confirm that it does work when passed the address of a DLL user space
>> function? In any case this definitely won't work on Linux.
>>
>> I searched for "how to call a function in a shared library in go" in
>> Chrome and the results included an AI generated example of how to do this
>> along with links to many articles and other sources such as StackOverflow.
>> If you're still having problems ask again but show us the source code you
>> wrote and the commands you ran to compile it.
>>
>> --
>> Kurtis Rader
>> Caretaker of the exceptional canines Junior and Hank
>>
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