Re: macro expansion and types in <sys/types.h>

["OBATA Akio" <obata%lins.jp@localhost>]

Hi,

On Fri, 05 Sep 2014 13:31:43 +0900, Brook Milligan <brook%nmsu.edu@localhost> 
wrote:

> I am building a package (samtools if anyone cares) that tries to define some 
> functions with c preprocessor macro expansions.  In doing so it uses type names 
> (e.g., uint16_t) as both part of the function name as well as one of the types 
> within the function definition.  However, in some but not all places the macro 
> expansion leads to extra underscores being prepended, i.e., uint16_t is 
> sometimes expanded as __uint16_t.
>
> This is clearly a result of lines like the following in <sys/types.h>:
>
> #ifndef uint16_t
> typedef __uint16_t      uint16_t;
> #define uint16_t        __uint16_t
> #endif

It's also in <stdint.h>.

I feel it is bad idea to define it in both sys/types.h and stdint.h, and use 
"uint16_t"
as a multiple definition guard name.

> The problem is that the extra underscores that are added to the function names 
> do not match function calls elsewhere without them.
>
> Here is a much simplified example.  Running the following through gcc -E
>
> #include <sys/types.h>
>
> #define M0(x) void name_##x() { }
> #define M1(x, y) void name_##x(y) { }
> #define M2(x) M1(x,x)
>
> M0(uint16_t)
> M1(uint16_t,uint16_t)
> M2(uint16_t)
>
> yields the following (omitting all the stuff from sys/types.h):
>
> void name_uint16_t() { }
> void name_uint16_t(__uint16_t) { }
> void name___uint16_t(__uint16_t) { }
>
> I would appreciate some input from the c preprocessor wizards among you 
> regarding how to fix this problem.
>
> Thanks for your help.


I don't know your situation well, but I've added following patches for the 
issue:
  devel/gobject-introspection/patches/patch-aa
  lang/jamvm/patches/patch-src_interp_engine_interp.h

--
OBATA Akio / obata%lins.jp@localhost