Use type-generic macros

[leo60228]

According to the README:

There is no free C++ compiler for MCS51 chip, we can not use polymorph functions. So you can not expect the compiler will choose a function according to the parameter's type.

C11 adds _Generic for this purpose. Here's a trivial example: https://godbolt.org/z/Yv8sznf3v

However, this currently can't be used for print due to an SDCC bug.

[DeqingSun]

@leo60228 thanks for this info. I'll check if this can be implemented into the package.

[DeqingSun]

@leo60228 Frankly speaking I have no idea what "_Generic" means or how it compiles (yet). But it seems work. I'll see how to add it into the package.

[leo60228]

_Generic is a relatively new feature (C99 had polymorphic functions in the standard library, but those were implemented in a compiler-specific way until C11). SDCC supports it but there's several open bugs. I don't think it's usable for print yet, but it could be with some bugfixes, and might be useful for other functions.

[DeqingSun]

@leo60228 Sorry I ask the question before I learn some basics about _Generic. Why you think it is not usable for print? It seems my sketch compiles and works as expected.

[leo60228]

There's a cryptic compiler error if you use it with a pointer, which is why char* was commented out. I linked an existing bug report for this in the original issue.

On Wed, Sep 29, 2021, 9:13 AM Deqing Sun @.***> wrote:

@leo60228 https://github.com/leo60228 Sorry I ask the question before I learn some basics about _Generic. Why you think it is not usable for print? It seems my sketch compiles and works as expected.

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[DeqingSun]

@leo60228 Thank you and I get it when trying to use the pointer.

Internal error: validateLink failed in SPEC_NOUN(type) @ /Users/sdcc-builder/build/sdcc-build/orig/sdcc/src/SDCCast.c:5401: expected SPECIFIER, got DECLARATOR

I'll subscribe to that ticket and see when it get fixed. Not supporting pointer makes implementing the _Generic to print pointless.

[DeqingSun]

Update: The bug fixing is now funded. Wish it get fixed soon

https://sourceforge.net/p/sdcc/wiki/SDCC-STD-UX/

[DeqingSun]

Generic is functional after SDCC commit 13402.

This repo now supports Generic for print.

https://github.com/DeqingSun/ch55xduino/blob/ch55xduino/ch55xduino/ch55x/cores/ch55xduino/genericPrintSelection.h