Re: [PATCH 1/2] Compiler Attributes: add support for __fallthrough (gcc >= 7.1)

[Theodore Y. Ts'o]

On Sun, Oct 21, 2018 at 05:42:18PM -0700, Matthew Wilcox wrote:
> On Sun, Oct 21, 2018 at 07:14:13PM +0200, Miguel Ojeda wrote:
> > +#if __has_attribute(__fallthrough__)
> > +# define __fallthrough                  __attribute__((__fallthrough__))
> > +#else
> > +# define __fallthrough
> > +#endif
> 
> Why is the #else not:
> 
> # define __fallthrough		/* fallthrough */
> 
> Would this solve the Coverity problem, or does Coverity look at the raw
> source code before preprocessing?

Wouldn't the "/* ... */" be eaten by the preprocessor before defining
the __fallthrough cpp macro?  (e.g., try running the attached script)

						- Ted



#!/bin/bash

cat << EOF > /tmp/test$$.c
#define foobar quux /* foobar */

foobar
EOF
gcc -E /tmp/test$$.c
rm -f /tmp/test$$.c