C compiler: missing diagnostics: result of ## operator is not a valid preprocessing token

[pmor]

Per C11 this leads to UB:

#define X . ## . ## .
X

Intel C compiler does not diagnose it:

$ icc t0.c -std=c11 -Wall -Wextra -pedantic -E
<nothing>

As a quality-of-implementation matter Intel C compiler should diagnose it.
Version: icc 2021.1.2 on x86-64 on Linux

[DitiD_Intel]

Hi,

Thanks for reporting to us.

We're working on it and we'll get back to you soon.

Thanks and Regards,

Ditipriya.

[Viet_H_Intel]

Thanks,

I've reported this case to our Front End team.

Regards.

Viet

[Viet_H_Intel]

Since the classic C/C++ compilers will enter “Legacy Product Support” mode signaling the end of regular updates to the classic compiler base, and they will no longer appear in oneAPI toolkits, we will not fix this diagnostic in icc.

Please see: https://www.intel.com/content/www/us/en/developer/articles/technical/adoption-of-llvm-complete-icx.html.

I am going to close this as "won't fix".

Regards,

Viet