llvm dev - May 2018 - Global Variable Initialization via Internal Function

Hello,

I'm trying to figure out how to initialize global variables via LLVM IR and
I found that clang creates a internal function to initialize global
variables if initialization values are not constants.

*Do we really need to create an internal function for complex global
variable initializations during variable declaration? Can't we create
instructions in global scope?*

Example Simple C++ code:

int func()
{
    return 5*2;
}

init globalVar = func();

int main(...)
...

Thanks for helping!

Aaron
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On Mon, May 7, 2018 at 2:43 PM Aaron via llvm-dev <llvm-dev at
lists.llvm.org>
wrote:
> Hello,
> I'm trying to figure out how to initialize global variables via LLVM IR
and I found that clang creates a internal function to initialize global
variables if initialization values are not constants.
> Do we really need to create an internal function for complex global
variable initializations during variable declaration? Can't we create
instructions in global scope?


There might be other ways, but the C++ standard says something about the
order of initialisation of objects, and operating systems usually do this
by a convention. The convention seems to be that it will call functions
that are referred to from specially-named sections in a binary. So far, the
"cleanest" way of doing that is to define functions that get referred
to
(by address) from these special sections.
> Example Simple C++ code:
> int func()
> {
>      return 5*2;
> }
> init globalVar = func();
> int main(...)
> ...
> Thanks for helping!
> Aaron
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev


-- 
Dean