Example: provenance_via_io_percentp_global.c

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    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <inttypes.h>
    int x=1;
    int main() {
      int *p = &x;
      FILE *f = fopen(
        "provenance_via_io_percentp_global.tmp","w+b");
      printf("Addresses: p=%p\n",(void*)p);
      // print pointer address to a file
      fprintf(f,"%p\n",(void*)p);
      rewind(f);
      void *rv;
      int n = fscanf(f,"%p\n",&rv);
      int *r = (int *)rv;
      if (n != 1) exit(EXIT_FAILURE);
      printf("Addresses: r=%p\n",(void*)r);
      // are r and p now equivalent?  
      *r=12; // is this free of undefined behaviour?                                                           
      _Bool b1 = (r==p); // do they compare equal?                      
      _Bool b2 = (0==memcmp(&r,&p,sizeof(r)));//same reps?
      printf("x=%i *r=%i b1=%s b2=%s\n",x,*r,
             b1?"true":"false",b2?"true":"false");
    }
[link to run test in Cerberus]

Experimental data (what does this mean?) 



cerberus-concrete-PVI exit codes: compile 0 / execute 1
provenance_via_io_percentp_global.c:17:20: error: use of undeclared identifier '__cerbvar_EXIT_FAILURE'
  if (n != 1) exit(EXIT_FAILURE);
                   ^
§6.5.1#2: 
2   An identifier is a primary expression, provided it has been declared as designating an
    object (in which case it is an lvalue) or a function (in which case it is a function
    designator).91)


cerberus-concrete-PNVI exit codes: compile 0 / execute 1
provenance_via_io_percentp_global.c:17:20: error: use of undeclared identifier '__cerbvar_EXIT_FAILURE'
  if (n != 1) exit(EXIT_FAILURE);
                   ^
§6.5.1#2: 
2   An identifier is a primary expression, provided it has been declared as designating an
    object (in which case it is an lvalue) or a function (in which case it is a function
    designator).91)


gcc-8.1-O0 Addresses: p=0x600cf0
Addresses: r=0x600cf0
x=12 *r=12 b1=true b2=true


gcc-8.1-O2 Addresses: p=0x600c38
Addresses: r=0x600c38
x=12 *r=12 b1=true b2=true


gcc-8.1-O3 Addresses: p=0x600c38
Addresses: r=0x600c38
x=12 *r=12 b1=true b2=true


gcc-8.1-O2-no-strict-aliasing Addresses: p=0x600c38
Addresses: r=0x600c38
x=12 *r=12 b1=true b2=true


gcc-8.1-O3-no-strict-aliasing Addresses: p=0x600c38
Addresses: r=0x600c38
x=12 *r=12 b1=true b2=true


clang-6.0-O0 Addresses: p=0x601068
Addresses: r=0x601068
x=12 *r=12 b1=true b2=true


clang-6.0-O2 Addresses: p=0x601060
Addresses: r=0x601060
x=12 *r=12 b1=true b2=true


clang-6.0-O3 Addresses: p=0x601060
Addresses: r=0x601060
x=12 *r=12 b1=true b2=true


clang-6.0-O2-no-strict-aliasing Addresses: p=0x601060
Addresses: r=0x601060
x=12 *r=12 b1=true b2=true


clang-6.0-O3-no-strict-aliasing Addresses: p=0x601060
Addresses: r=0x601060
x=12 *r=12 b1=true b2=true


clang-6.0-UBSAN Addresses: p=0x632b80
Addresses: r=0x632b80
x=12 *r=12 b1=true b2=true


clang-6.0-ASAN Addresses: p=0x716b80
Addresses: r=0x716b80
x=12 *r=12 b1=true b2=true


clang-6.0-MSAN Addresses: p=0x6b7b00
Addresses: r=0x6b7b00
x=12 *r=12 b1=true b2=true


icc-19-O0 Addresses: p=0x600e70
Addresses: r=0x600e70
x=12 *r=12 b1=true b2=true


icc-19-O2 Addresses: p=0x6046e0
Addresses: r=0x6046e0
x=12 *r=12 b1=true b2=true


icc-19-O3 Addresses: p=0x6046e0
Addresses: r=0x6046e0
x=12 *r=12 b1=true b2=true


icc-19-O2-no-strict-aliasing Addresses: p=0x6046e0
Addresses: r=0x6046e0
x=12 *r=12 b1=true b2=true


icc-19-O3-no-strict-aliasing Addresses: p=0x6046e0
Addresses: r=0x6046e0
x=12 *r=12 b1=true b2=true


compcert-3.4 Addresses: p=0x601068
Addresses: r=0x601068
x=12 *r=12 b1=true b2=true


compcert-3.4-O Addresses: p=0x601068
Addresses: r=0x601068
x=12 *r=12 b1=true b2=true


kcc-1.0 exit codes: compile 0 / execute 139
Addresses: p=(nil)
Addresses: r=(nil)
Dereferencing a null pointer:
      > in main at provenance_via_io_percentp_global.c:20:3

    Undefined behavior (UB-CER3):
        see C11 section 6.5.3.2:4 http://rvdoc.org/C11/6.5.3.2
        see C11 section J.2:1 item 43 http://rvdoc.org/C11/J.2
        see CERT-C section EXP34-C http://rvdoc.org/CERT-C/EXP34-C
        see MISRA-C section 8.1:3 http://rvdoc.org/MISRA-C/8.1

Execution failed (configuration dumped)