ivorykite

reverse polish calculator in gcc

gcc makes it possible to code this RPN interpreter more compactly than C89..C11

//RPN calculator: E:EEf|n f:[+-*/] n:[0-9]
typedef int I;typedef long J;typedef char C,*S;typedef J(*F)(J*);I printf(S,...);I(*O)(S,...)=printf;
#define R return
#define W(x,y...) while(x){y;}
#define K(m) m(+)m(-)m(*)m(/)
#define L(o) ""#o
#define M(o) ({J _f(J*x){R x[0] o x[1];}_f;}),
I main(I c,S*v)
{if(c!=2)R O("use: %s 12+3-\n",*v);
 J s[99],*t=s;;J push(J x){R *t++=x;}J*pop(I n){R t-=n;}J jsc(S s,C c){S t=s;W(*t&&c!=*t,t++)R t-s;}
 C o[]=K(L);F f[]={K(M)0};S e=v[1];W(*e,push(*e>47?*e-'0':f[jsc(o,*e)](pop(2))),e++)R O("%ld\n",*pop(1));
}

//RPN calculator: E:EEf|n f:[+-*/] n:[0-9]

typedef int I;typedef long J;typedef char C,*S;typedef J(*F)(J*);I printf(S,...);I(*O)(S,...)=printf;

#define R return

#define W(x,y...) while(x){y;}

#define K(m) m(+)m(-)m(*)m(/)

#define L(o) ""#o

#define M(o) ({J _f(J*x){R x[0] o x[1];}_f;}),

I main(I c,S*v)

{if(c!=2)R O("use: %s 12+3-\n",*v);

J s[99],*t=s;;J push(J x){R *t++=x;}J*pop(I n){R t-=n;}J jsc(S s,C c){S t=s;W(*t&&c!=*t,t++)R t-s;}

C o[]=K(L);F f[]={K(M)0};S e=v[1];W(*e,push(*e>47?*e-'0':f[jsc(o,*e)](pop(2))),e++)R O("%ld\n",*pop(1));

}

call functions on the run – x86_64

It doesn’t take much to call an x86_64 function by its address and an array of arguments. The technique is useful for implementing interpreters or responding to remote procedure calls. Supports 4 args, but can be completed by adding rcx, r8, r9. Extend using XMM floating point registers.

//x86_64 ABI - include this file for call and vcall.  gcc -DTEST x.c && ./a.out  (c) 2016 jack andrews
#define _GNU_SOURCE 
#include<stdarg.h>
#include<stdio.h>
#include<stdlib.h>
#define R return
#define _ static inline
typedef int I;typedef long J;typedef void V;typedef char*S;
_ J call(V*f,J n,V*a)
{J r;switch(n)
#define M(x,b) case x:asm ("movq %0,%%r"#b";"::"g"(((J*)a)[x-1]):"%r"#b)
 {M(4,cx);M(3,dx);M(2,si);M(1,di);case 0:asm ("push %%rbp;call *%1;pop %%rbp":"=a"(r):"g"(f):);break;default: R *(J*)0;
}}
_ J vcall(V*f,V*x,V*y,...){J r;va_list l;va_start(l,y);V*a[]={x,y,l};r=call(f,3,a);va_end(l);R r;}
#ifdef TEST
#define A(x,y) {I r;if(x!=(r=y))exit(fprintf(stderr,"line %d ?%d\n",__LINE__,r));}
J O2(S x,S y){R (J)fprintf(stdout,x,y);}
I main()
{S t;I x=call(atol,1,(S[]){"32"});
 A(2,vcall(vasprintf,&t,"%ld",x))
 A(3,call(O2,2,(S[]){"%s\n",t})) /*expect 32*/
 free(t);R 0;
}
#endif

#define _GNU_SOURCE

#include<stdarg.h>

#include<stdio.h>

#include<stdlib.h>

#define R return

#define _ static inline

typedef int I;typedef long J;typedef void V;typedef char*S;

_ J call(V*f,J n,V*a)

{J r;switch(n)

#define M(x,b) case x:asm ("movq %0,%%r"#b";"::"g"(((J*)a)[x-1]):"%r"#b)

{M(4,cx);M(3,dx);M(2,si);M(1,di);case 0:asm ("push %%rbp;call *%1;pop %%rbp":"=a"(r):"g"(f):);break;default: R *(J*)0;

}}

_ J vcall(V*f,V*x,V*y,...){J r;va_list l;va_start(l,y);V*a[]={x,y,l};r=call(f,3,a);va_end(l);R r;}

#ifdef TEST

#define A(x,y) {I r;if(x!=(r=y))exit(fprintf(stderr,"line %d ?%d\n",__LINE__,r));}

J O2(S x,S y){R (J)fprintf(stdout,x,y);}

I main()

{S t;I x=call(atol,1,(S[]){"32"});

A(2,vcall(vasprintf,&t,"%ld",x))

A(3,call(O2,2,(S[]){"%s\n",t})) /*expect 32*/

free(t);R 0;

}

#endif