前綴的可變參數宏指向另一個宏

Question

每個參數假設，我有這些宏開頭爲ATTRIB_

#define ATTRIB_A "a" 
#define ATTRIB_B "b" 
#define ATTRIB_C "c" 

我想能夠使用解包每個給定的參數可變參數宏然後用ATTRIB_前綴是爲了獲得一個屬性宏的全名展開宏：

#define ATTRIBS(...) CONFUSED_HERE(##__VA_ARGS__) 

這將用作：

const char * a = ATTRIBS(A, B, C); 

其結果將等於：就好像使用像（除了短）

const char * a = "a" "b" "c"; 

：

ATTRIBS(ATTRIB_A, ATTRIB_B, ATTRIB_C); 

請注意，這不是這個宏的實際使用。我很好奇如何將前綴應用於可變宏的每個參數以訪問/擴展另一個宏。

只要它適用於最近的MinGW/GCC編譯器，我並不關心可移植性。如果他們帶有一些我不知道的擴展名。

Answer 1

從foreach-macro-on-macros-arguments

#define PP_NARG(...) PP_NARG_(__VA_ARGS__,PP_RSEQ_N()) 
#define PP_NARG_(...) PP_ARG_N(__VA_ARGS__) 

#define PP_ARG_N(\ 
     _1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \ 
     _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \ 
     _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \ 
     _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \ 
     _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \ 
     _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \ 
     _61,_62,_63,N,...) N 

#define PP_RSEQ_N() \ 
     63,62,61,60,     \ 
     59,58,57,56,55,54,53,52,51,50, \ 
     49,48,47,46,45,44,43,42,41,40, \ 
     39,38,37,36,35,34,33,32,31,30, \ 
     29,28,27,26,25,24,23,22,21,20, \ 
     19,18,17,16,15,14,13,12,11,10, \ 
     9,8,7,6,5,4,3,2,1,0 


/* need extra level to force extra eval */ 
#define Paste(a,b) a ## b 
#define XPASTE(a,b) Paste(a,b) 


/* APPLYXn variadic X-Macro by M Joshua Ryan  */ 
/* Free for all uses. Don't be a jerk.   */ 
/* I got bored after typing 15 of these.   */ 
/* You could keep going upto 64 (PPNARG's limit). */ 
#define APPLYX1(a)   X(a) 
#define APPLYX2(a,b)   X(a) X(b) 
#define APPLYX3(a,b,c)  X(a) X(b) X(c) 
#define APPLYX4(a,b,c,d)  X(a) X(b) X(c) X(d) 
#define APPLYX5(a,b,c,d,e) X(a) X(b) X(c) X(d) X(e) 
#define APPLYX6(a,b,c,d,e,f) X(a) X(b) X(c) X(d) X(e) X(f) 
#define APPLYX7(a,b,c,d,e,f,g) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) 
#define APPLYX8(a,b,c,d,e,f,g,h) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) 
#define APPLYX9(a,b,c,d,e,f,g,h,i) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) 
#define APPLYX10(a,b,c,d,e,f,g,h,i,j) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) X(j) 
#define APPLYX11(a,b,c,d,e,f,g,h,i,j,k) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) X(j) X(k) 
#define APPLYX12(a,b,c,d,e,f,g,h,i,j,k,l) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) X(j) X(k) X(l) 
#define APPLYX13(a,b,c,d,e,f,g,h,i,j,k,l,m) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) X(j) X(k) X(l) X(m) 
#define APPLYX14(a,b,c,d,e,f,g,h,i,j,k,l,m,n) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) X(j) X(k) X(l) X(m) X(n) 
#define APPLYX15(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o) \ 
    X(a) X(b) X(c) X(d) X(e) X(f) X(g) X(h) X(i) X(j) X(k) X(l) X(m) X(n) X(o) 
#define APPLYX_(M, ...) M(__VA_ARGS__) 
#define APPLYXn(...) APPLYX_(XPASTE(APPLYX, PP_NARG(__VA_ARGS__)), __VA_ARGS__) 


#define ATTRIB_A "a" 
#define ATTRIB_B "b" 
#define ATTRIB_C "c" 


#define X(a) XPASTE(ATTRIB_, a) 

#define ATTRIBS(...) APPLYXn(__VA_ARGS__) 

int main() 
{ 
    const char * a = ATTRIBS(A, B, C); 

    std::cout << a << std::endl; 
} 

Demo