Creating a microcontroller startup file

[Mike via Digitalmars-d-learn]

On Tuesday, 7 April 2015 at 20:33:26 UTC, Jens Bauer wrote:

>
> Question number 2: Is it possible to change the VectorFunc to 
> be a real function pointer, rather than a void* ?
>

I did something along these lines (modified to match your 
example) and it worked fine for me:

alias VectorFunc = void function();

@attribute("weak") @attribute("alias", "defaultHandler")
extern void Reset_Handler();

@attribute("weak") @attribute("alias", "defaultHandler")
extern void NMI_Handler()

@attribute("weak") @attribute("alias", "defaultHandler")
extern void HardFault_Handler();

@attribute("section",".isr_vector.ro")
immutable ISR[3] g_pfnVectors =
[
       &Reset_Handler
     , &NMI_Handler
     , &HardFault_Handler
];

I did this before "weak", "alias", and "section" attributes were 
added, however.  To see my original code, look at the slide in 
the presentation here: https://youtu.be/o5m0m_ZG9e8?t=2332.  My 
original code had everything decorated with extern(C) as well so 
I could refer to the symbol directly in my linker scripts.  That 
may not be needed for you, so I left it out.

> Question number 3: How can I call an external function and keep 
> the binary file size down ?

Are you compiling with -ffunction-sections -fdata-sections and 
linking with --gc-sections? You may need to in order to get rid 
of some things.

What do you using for your D runtime?  Perhaps some code in your 
runtime is implicitly linking to some code you're not directly 
calling.

I also add the following to my linker scripts to get rid of stuff 
I don't find necessary:

/DISCARD/ :
{
    *(.ARM.extab*)
    *(.ARM.exidx*)
}

/DISCARD/ :
{
    *(.ARM.attributes*)
    *(.comment)
}

You can see the latest incarnation of my linker script here: 
https://github.com/JinShil/stm32f42_discovery_demo/blob/master/linker/linker.ld


> Question number 4: How can I reduce the function declaration of 
> the Reset_Handler and NMI_Handler shown above ?

Try something along these lines.

enum weak = gcc.attribute.attribute("weak");
enum isrDefault = gcc.attribute.attribute("alias", 
"defaultHandler");

extern @weak @isrDefault void NMI_Handler();
extern @weak @isrDefault void HardFault_Handler();

I use this idiom briefly in my code here: 
https://github.com/JinShil/stm32f42_discovery_demo/blob/master/source/start.d

The enum thing kinda bugs me about D, but you'll see it used 
everywhere, especially phobos.  It's called a manifest constant, 
and you can find a short blurb about it at the bottom of this 
page:  http://dlang.org/enum.html

Mike