C++ macro arguments

Question

#define ImplBaseRTTI(classname) RuntimeClass classname::rtti(NULL);
#define ImplRTTI(classname, b1) RuntimeClass classname::rtti(&b1::rtti, NULL)
#define ImplRTTI2(classname, b1, b2) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, NULL)
#define ImplRTTI3(classname, b1, b2, b3) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, &b3::rtti, NULL)
#define ImplRTTI4(classname, b1, b2, b3, b4) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, &b3::rtti, &b4::rtti, NULL)
#define ImplRTTI5(classname, b1, b2, b3, b4, b5) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, &b3::rtti, &b4::rtti, &b5::rtti, NULL)
#define ImplRTTI6(classname, b1, b2, b3, b4, b5, b6) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, &b3::rtti, &b4::rtti, &b5::rtti, &b6::rtti, NULL)
#define ImplRTTI7(classname, b1, b2, b3, b4, b5, b6, b7) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, &b3::rtti, &b4::rtti, &b5::rtti, &b6::rtti, &b7::rtti, NULL)
#define ImplRTTI8(classname, b1, b2, b3, b4, b5, b6, b7, b8) RuntimeClass classname::rtti(&b1::rtti, &b2::rtti, &b3::rtti, &b4::rtti, &b5::rtti, &b6::rtti, &b7::rtti, &b8::rtti, NULL)

How can I change this code like

#define ImplRTTI(classname, ...) RuntimeClass classname::rtti(&__VA_ARGS__::rtti, NULL)

It doesn't matter this code needs to become very long or complicated if I can use this macro with only ImplRTTI.

Sorry, stupid question, but what does `RuntimeClass classname::rtti(&b1::rtti, NULL)` do / what is the purpose of your macro? What you want is possible (see e.g. https://stackoverflow.com/questions/6194031/iterating-variadic-macro-arguments) but I don't think the necessary macro magic is with it. Also, I haven't checked it, but boost.preprocessor might provide a convenient solution. — MikeMB, Jul 29 '17 at 08:43

score 0 · Answer 1 · answered Jul 29 '17 at 09:08

From 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__)

And now

#define X(b) &b::rtti,

#define ImplBaseRTTI(classname) RuntimeClass classname::rtti(NULL)
#define ImplRTTI(classname, ...) \
    RuntimeClass classname::rtti(APPLYXn(__VA_ARGS__) NULL)

score -1 · Answer 2 · answered Jul 29 '17 at 08:43

-1

See my own question and answer. Be very careful with macroses, because in 99% cases their are unnecessary and painful. I ended up with fully redesign of my project and removing almost all macroses.

answered Jul 29 '17 at 08:43

Green_Wizard

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C++ macro arguments

2 Answers2