Am 21.10.2011, 10:32 Uhr, schrieb Gor Gyolchanyan
<[email protected]>:
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
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
Maybe these cases can often be solved when, as you say, they are for
compatibility with other compilers. The header converter would simply
assume to be the latest and greatest of the known compilers and evaluate
the code like this:
- there is an #ifdef
- if it a define from the list of "known C compilers with quirks"
- jump right to the else block
The #define obviously can become more than one thing in the .d file. But
that is determined by the instantiation site. The above CONST would
probably be ignored when it is used in a const parameter declaration,
because of D's transitivity and become 'immutable __gshared' when used on
a global variable. Do you get the idea?
