Allow multiple declarators in a declaration

[ChrisDodd]

Some people consider multiple declarators in a declaration as one of the big mistakes of C, and think they should never be used. Some coding standards require that every variable be declared in a separate declaration, as P4 currently requires.

Other people coming to P4 from C or C++ are annoyed by this restriction, and try to write code with multiple declarators.

This change allows such declarations as an extension, and can warn about them as a non-standard extension.

[asl]

Can we have testcase for this, please?

[ChrisDodd]

Can we have testcase for this, please?

One (small) testcase added.

[fruffy]

Seems like it should be a command-line option to toggle these extensions on/off.

[ChrisDodd]

Seems like it should be a command-line option to toggle these extensions on/off.

There is a command line option to turn the warnings on/off (--Wwarn=extension vs --Wdisable=extension) Should the default be warnings on or off?

[fruffy]

There is a command line option to turn the warnings on/off (--Wwarn=extension vs --Wdisable=extension) Should the default be warnings on or off?

Hmm, for practical reasons this seems like a pedantic mode.

I was mostly thinking to have a way to toggle extensions on/off in general. This way we could also prototype more work not compliant with the spec.

[ChrisDodd]

There is a command line option to turn the warnings on/off (--Wwarn=extension vs --Wdisable=extension)

I was mostly thinking to have a way to toggle extensions on/off in general. This way we could also prototype more work not compliant with the spec.

--Werror=extension makes any use of an extension an error, effectively turning them off