[vim/vim] C syntax highlighting bug with uncommented #include (#5705)

[Bogdan Barbu]

Try the following:
/* */ #include <stdio.h>
or
/*
*/ #include <stdio.h>

The directive #include will not be highlighted.

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[Christian Brabandt]

Is that actually valid syntax?

> Am 27.02.2020 um 21:53 schrieb Bogdan Barbu <notifi...@github.com>:
>
> 

[Mike Williams]

On Friday, 28 February 2020 06:21:20 UTC, Christian Brabandt wrote:

Is that actually valid syntax?

It is valid syntax. According to the standard all comments are replaced with spaces before executing pre-processor directives like #include. This means any directive can appear after a comment. Not a typical coding convention but perfectly valid.

[Bogdan Barbu]

Yes. According to section 5.1.1.2 of the C standard, comments are replaced by a space character before #include preprocessing directives are interpreted. Also, tested with GCC, just in case.

[Bogdan Barbu]

What you probably had in mind was something along the lines of:

#define EMPTY
EMPTY #include <stdio.h>

where #include is indeed not a preprocessing directive because EMPTY will not have been replaced at the end of the 4th translation phase, as defined in the specification. This already works as expected.

[Bram Moolenaar]

Not all valid syntax can be recognized. The highlighting is pattern based, it is not a full parser.
This construct is unusual enough that we don't need to support it.
I would discourage writing it like that anyway, better put the comment above the #include.

[Bram Moolenaar]

Closed #5705.