The CAPI Manifesto

[Michel Fortin]

On 2011-10-17 13:41:14 +0000, Jacob Carlborg <doob at me.com> said:

> On 2011-10-17 14:01, Michel Fortin wrote:
>> On 2011-10-17 10:21:45 +0000, Sean Kelly <sean at invisibleduck.org> said:
>> 
>>> There's also the occasional issue of something that doesn't translate
>>> into D. As one slightly weird example, some of the the Posix routines
>>> in OSX have alternates with odd suffixes like "$2003" that are the
>>> versions which should be called on newer versions of the OS. I'm still
>>> not sure of the best way to handle this, since D doesn't have macros.
>> 
>> I think what D needs to handle that is some pragma to manually specify
>> the mangled name of a given function. Why would you need macros?
> 
> Perhaps the macro is used to determine if "foo" or "foo$2003" is 
> supposed to be called, based on some condition.

Indeed. The condition is which OS release you're targeting. That can be 
accomplished today through static ifs. Although it'd be a little more 
verbose since you'd have to repeat the function prototype.

If we had a way to do conditional attributes in D it'd be awesome for 
this use case. It could work this way for instance:

	static if (MAC_OS_X_VERSION_MIN_REQUIRED == 10.5)
		@deprecated_in_os_x_10_5 = deprecated;
	else
		@deprecated_in_os_x_10_5 = /* nothing */;

	@deprecated_in_os_x_10_5
	void some_function_deprecated_in_os_x_10_5();	
Or this way for the special mangled names:

	static if (MAC_OS_X_VERSION_MIN_REQUIRED == 10.5)		@darwin_alias(name) 
= pragma(symbol_name, name ~ "$UNIX2003");
	else
		@darwin_alias(name) = pragma(symbol_name, name);

	@darwin_alias("fwrite")
	size_t fwrite(const void * /*__restrict*/, size_t, size_t, FILE * 
/*__restrict*/);

Internally, when the compiler sees @darwin_alias("fwrite") it just 
replaces it with the attributes @darwin_alias was supposed to be. Note 
that I'm *not* proposing a macro system: this would work at the 
semantic level as a special kind of attribute.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/