Re: VxWorks Patches Back from the Dead!

[Paolo Bonzini <bonzini at gnu dot org>]

Il 23/08/2012 13:46, rbmj ha scritto:
> On 8/23/2012 4:24 AM, Paolo Bonzini wrote:
>> Some comments on the patches:
>>
>>> +    c_fix_arg    = "%0\n"
>>> +        "#define ioctl(fd, func, arg) ((ioctl)((fd), (func),
>>> ((int)(arg))))\n";
>> This can be simply
>>
>> #define ioctl(fd, func, arg) ioctl(fd, func, (int)arg)
>>
>> thanks to C and cpp precedence rules.
> 
> OK.  I just over-parenthesize all function-macros by default because I
> can never remember the rules exactly and worry about not anticipating
> what someone puts in a macro.
>>> +    c_fix_arg    = "%0\n"
>>> +        "#ifdef IN_GCC\n"
>>> +        "#define mkdir(dir, mode) ((mode), (mkdir)(dir))\n"
>>> +        "#endif\n";
>> Are you sure about the #ifdef/#endif?  In fact, you definitely do not
>> want a _global_ include to have a dependency on a user symbol.
> The idea is I don't want to break existing code, so I only want this
> macro to take effect inside of GCC proper, as (AFAIK) anything built
> with the new compiler gets the fixed includes, and there's lots of
> VxWorks code that relies on single-argument mkdir.
> The alternative is varaidic macros, but I'm no expert on the nuances of
> c89 vs c99 variadic macros.

Something like this should work:

#define mkdir(dir, ...) ((void)0, ##__VA_ARGS, (mkdir)(dir))

>>> Subject: [PATCH 10/10] Make open() call more compatible in gcc/gcov-io.c
>>>
>>> In gcc/gcov-io.c, the call to open() only has two arguments. This
>>> is fine, as long as the system open() is standards compliant.
>> So you have to add another fixincludes hack, adding a macro indirection
>> like the one you have for ioctl:
>>
>> #define open(a, b, ...)      __open(a, b , ##__VA_ARGS__, 0660)
>> #define __open(a, b, c, ...) (open)(a, b, c)
> 
> Again, just not sure about variadic macro compatibility.  If that will
> work for both c89 and c99 and c++, then that looks good to me.

Yes, GCC has variadic macros as an extension in C89 mode too.  You need
to experiment a bit with -pedantic and/or -ansi and/or -std=c89, though.

Paolo