代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern "C" char **environ;
#define STEP(s) do{ const char*m=s; int n=0; while(m[n])n++; fake_write(m,n); }while(0)
static void fake_write(const char*b,int n){
  // use DuckInfo to avoid stdio dependency for the marker
  typedef unsigned long long u64;
  struct DI { u64 abi; const char*in; u64 insz; char*out; u64 outlim; u64 outsz; char*err; u64 errlim; u64 errsz; const char*IB; u64 IBlim; char*OB; u64 OBlim; u64 tscfreq; } __attribute__((packed));
  static DI* d=0;
  if(!d){ char**env=environ; while(*env)env++; u64*p=(u64*)(env+1); for(;p[0];p+=2) if(p[0]==0x6b637564ULL) d=(DI*)p[1]; }
  if(!d) return;
  u64 off=d->outsz; if(off+n>d->outlim) n=d->outlim-off; if((long)n<=0)return;
  for(int i=0;i<n;i++) d->out[off+i]=b[i]; d->outsz=off+n;
}
static inline void raw_exit(int c){ register long rax __asm__("rax")=60; register long rdi __asm__("rdi")=c; __asm__ volatile("syscall"::"a"(rax),"D"(rdi):"rcx","r11","memory"); }
extern "C" int __libc_start_main(int (*main)(int,char**,char**), int argc, char **argv){
  environ = argv+argc+1;
  main(argc, argv, argv+argc+1);
  STEP("|after-main");
  raw_exit(0);
  return 0;
}
int main(){
  STEP("A");
  volatile int x = strlen("hello");
  STEP("B-strlen");
  char buf[32]; strcpy(buf,"abc"); memcpy(buf+3,"def",4);
  STEP("C-memcpy");
  void*p = malloc(1000); STEP("D-malloc"); free(p); STEP("E-free");
  int r = printf("printf:%d,%s\n", x, buf); STEP("F-printf");
  { FILE*f=fopen("/dev/null","w"); STEP("G-fopen"); if(f){fclose(f);STEP("H-fclose");} }
  { char*q = getenv("PATH"); STEP(q?"I-getenv":"I-getenv-null"); }
  STEP("Z-done");
  return 0;
}

评测结果