Feature request - a macro defined for GCC

[Jack Lloyd]

On Wed, Jul 02, 2008 at 03:47:49PM +0200, Vincent Lefevre wrote:
> On 2008-07-02 00:12:33 +0000, Joseph S. Myers wrote:
> > This internal binary no longer exists. Instead, there is a "cpp"
> > binary installed in the user binary directory, which calls the "cc1"
> > binary to do the same preprocessing as it does when compiling; that
> > is, it has the same effect as "gcc -E".
> 
> Not exactly:
> 
> vin% cpp -dM /dev/null | wc -l
> 128
> vin% gcc -E -dM /dev/null | wc -l
> gcc.real: /dev/null: linker input file unused because linking not done
> 0
> 
> Is it a bug of "gcc -E"?

Not really, it just doesn't understand it needs to treat an empty file as
C... instead you have to tell it so with -x c

(wks9 ~)$ cpp -dM /dev/null | wc -l
86
(wks9 ~)$ gcc -E -dM /dev/null | wc -l
gcc: /dev/null: linker input file unused because linking not done
0
(wks9 ~)$ gcc -E -x c -dM /dev/null | wc -l
86
(wks9 ~)$ gcc -E -x c++ -dM /dev/null | wc -l
92