Re: Question unused function parameter data garbage collection

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Sep 12, 2022 at 1:23 PM Fredrik Hederstierna via Gcc
<gcc@gcc.gnu.org> wrote:
>
> Hi,
>
> We have a function that does not used an in-parameter, simplified example:
>
> void test_unused_string_param_gc(const char* unused)
> {
>    // empty
> }
>
> Though when we have calls to this function, the arguments are still put in the memory, causing unnecessary flash memory usage for 'dead parameters'.
>
> Example if having a call (from another file) as
>
>       test_unused_string_param_gc("This string is not garbage-collected?");
>
> Then this string will still be added to our finally build binary?
>
> We compile with -Os, and have tried different flags to try get rid of this dead parameter data,
> do anyone know if this is the expected behavior and why? Or if we are missing any optimization flags, like LTO etc?

Without LTO there is no way the unused parameter can be elided on the
caller side so yes, try enabling LTO.

Richard.

> Best Regards,
> Fredrik
>