On 2011-10-21 10:32, Gor Gyolchanyan wrote:
That's ALL you can do in C. fill structs and call functions
(fundamental type manipulation doesn't count).
My personal research shows the following use cases of C macros (sorted
by popularity in descending order):
1. enum
2. alias (most notably, conditionally compiled ones)
3. CTFE function
4. mixin template
5. syntactic alias
6. syntactic mixin template
I guess it's quite difficult for a compiler to recognize the differences
between these use cases.
only the last 2 out of 6 cannot be translated to D.
An example of a syntactic alias is this very common piece of C code:
#ifdef __VERY_VERY_OLD_C_COMPILER__
#define CONST
#else
#define CONST const
#endif
An example of a syntactic mixin template is this piece of code, which
i never actually saw anywhere (possible only in C99 and C++):
#define N_TIMES(n) for(int i = 0; i != n; ++i)
The last use case is very rare. The only legitimate example i ever saw
is in libjpeg, where a macro is used to define function pointers of
API functions.
The use case before that is mostly used for portability reasons, which
is not necessary in D.
Some non-standard extension encapsulating macros are almost always
used in C libraries, which can be removed altogether.
The translation can go on regarding the above use cases and the last
two cases can be evaluated in-line, commented out and warned about for
manual translation.
Something similar is used in the Boost library for its "foreach" macro.
--
/Jacob Carlborg
