Examples of Python functions imitated using C language

def line_conf(a, b): def line(x): return a*x + b return line line1 = line_conf(1, 1) line2 = line_conf(4, 5) print(line1(5), line2(5))

/* MIT License Copyright (c) 2017 Yuandong-Chen Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ /////////////////////////////////////////////////////////////////////////////// // Note: The C program is almost equivalent to the Python program as follows: // def line_conf(a, b): // def line(x): // return a*x + b // return line // // line1 = line_conf(1, 1) // line2 = line_conf(4, 5) // print(line1(5), line2(5)) #include  #include  #include  #include  typedef int Func(); Func *line_conf(int x, int y,...) { va_list ap; va_start(ap, y); asm volatile( "push %%eax\n\t" "subl $40, %%esp\n\t" "movl 8(%%ebp), %%eax\n\t" "movl %%eax, -36(%%ebp)\n\t" "movl 12(%%ebp), %%eax\n\t" "movl %%eax, -40(%%ebp)\n\t" "addl $40, %%esp\n\t" "pop %%eax\n\t" :::"memory" ); if(va_arg(ap,int) == 1){ LINE: asm volatile( "push %%ebp\n\t" "movl %%esp, %%ebp\n\t" "movl 8(%%ebp), %%eax\n\t" "imul -36(%%ebp), %%eax\n\t" "addl -40(%%ebp), %%eax\n\t" "movl %%ebp, %%esp\n\t" "pop %%ebp\n\t" "ret\n\t" :::"memory","%eax" ); } END: va_end(ap); return (Func *)(&&LINE); } int main(int argc, const char *argv[]){ printf("====TEST START====\n"); printf("34*234+6 ?= %d\n",line_conf(34,6)(234)); printf("1*3+2 ?= %d; 324*65+3 ?= %d; 13*66+2 ?= %d\n",line_conf(1,2)(3),line_conf(324,3)(65),line_conf(13,2)(66)); int fd = line_conf(1,6)(4); Func *fun = line_conf(3,3); int a = 1; // Limited point printf("3*3+3 ?= %d; 1*4+6 ?= %d\n",fun(3),fd); printf("====TEST END====\n"); return 0; } // Compile it by the following command: // gcc -m32 -O0 -fno-stack-protector CFunctional.c; ./a.out // The terminal output should looks like: // ====TEST START==== // 34*234+6 ?= 7962 // 1*3+2 ?= 5; 324*65+3 ?= 21063; 13*66+2 ?= 860 // 3*3+3 ?= 12; 1*4+6 ?= 10 // ====TEST END==== //Note: The limitation happens between line 86 and line 88, we cannot insert any function here // whose stack is larger than 40 bytes.(Why is 40? check the inline assembler language)