Example: provenance_equality_global_xy.c

#include <stdio.h>
#include <string.h> 
int  x=1, y=2;
int main() {
  int *p = &x + 1;
  int *q = &y;
  printf("Addresses: p=%p q=%p\n",(void*)p,(void*)q);
  _Bool b = (p==q);
  // can this be false even with identical addresses?
  printf("(p==q) = %s\n", b?"true":"false");
  return 0;
}
[link to test in Cerberus and Compiler Explorer]

Experimental data (what does this mean?) 



gcc-8.1-O0 Addresses: p=0x6009b4 q=0x6009b4
(p==q) = true


gcc-8.1-O2 Addresses: p=0x600990 q=0x600988
(p==q) = false


gcc-8.1-O3 Addresses: p=0x600990 q=0x600988
(p==q) = false


gcc-8.1-O2-no-strict-aliasing Addresses: p=0x600990 q=0x600988
(p==q) = false


gcc-8.1-O3-no-strict-aliasing Addresses: p=0x600990 q=0x600988
(p==q) = false


clang-6.0-O0 Addresses: p=0x60103c q=0x60103c
(p==q) = true


clang-6.0-O2 Addresses: p=0x60103c q=0x60103c
(p==q) = true


clang-6.0-O3 Addresses: p=0x60103c q=0x60103c
(p==q) = true


clang-6.0-O2-no-strict-aliasing Addresses: p=0x60103c q=0x60103c
(p==q) = true


clang-6.0-O3-no-strict-aliasing Addresses: p=0x60103c q=0x60103c
(p==q) = true


clang-6.0-UBSAN Addresses: p=0x631b54 q=0x631b54
(p==q) = true


clang-6.0-ASAN Addresses: p=0x716b64 q=0x716ba0
(p==q) = false


clang-6.0-MSAN Addresses: p=0x6b7af4 q=0x6b7af4
(p==q) = true


icc-19-O0 Addresses: p=0x600ae4 q=0x600ae4
(p==q) = true


icc-19-O2 Addresses: p=0x6046c4 q=0x6046c4
(p==q) = true


icc-19-O3 Addresses: p=0x6046c4 q=0x6046c4
(p==q) = true


icc-19-O2-no-strict-aliasing Addresses: p=0x6046c4 q=0x6046c4
(p==q) = true


icc-19-O3-no-strict-aliasing Addresses: p=0x6046c4 q=0x6046c4
(p==q) = true


cerberus-concrete BEGIN EXEC[0]
Defined {value: "Specified(0)", stdout: "Addresses: p=<7>:76 q=<8>:76\n(p==q) = true\n", blocked: "false"}
END EXEC[0]
BEGIN EXEC[1]
Defined {value: "Specified(0)", stdout: "Addresses: p=<7>:76 q=<8>:76\n(p==q) = false\n", blocked: "false"}
END EXEC[1]
Time spent: 0.048650 seconds


cerberus-symbolic BEGIN EXEC[0]
Undefined [other_location(Core parser)]{id: [DUMMY(rev_listFromStr_aux)]}
END EXEC[0]
Time spent: 0.089327 seconds


gcc-4.9-shadowprov Addresses: p=0x414140 q=0x414138
(p==q) = false


CHERI:MIPS-O0 Addresses: p=0x30024 q=0x30024
(p==q) = true


CHERI:MIPS-O2 Addresses: p=0x30024 q=0x30024
(p==q) = true


CHERI:MIPS-O2-no-strict-aliasing Addresses: p=0x30024 q=0x30024
(p==q) = true


CHERI:CHERI-O0-uintcap-addr-exact-equals Addresses: p=0x120020014 q=0x120020014
(p==q) = false


CHERI:CHERI-O2-uintcap-addr-exact-equals Addresses: p=0x120020014 q=0x120020014
(p==q) = false


CHERI:CHERI-O2-no-strict-aliasing-uintcap-addr-exact-equals Addresses: p=0x120020014 q=0x120020014
(p==q) = false


CHERI:CHERI-O0-uintcap-offset-exact-equals Addresses: p=0x120020014 q=0x120020014
(p==q) = false


CHERI:CHERI-O2-uintcap-offset-exact-equals Addresses: p=0x120020014 q=0x120020014
(p==q) = false


CHERI:CHERI-O2-no-strict-aliasing-uintcap-offset-exact-equals Addresses: p=0x120020014 q=0x120020014
(p==q) = false


CHERI:CHERI-O0-uintcap-addr Addresses: p=0x120020014 q=0x120020014
(p==q) = true


CHERI:CHERI-O2-uintcap-addr Addresses: p=0x120020014 q=0x120020014
(p==q) = true


CHERI:CHERI-O2-no-strict-aliasing-uintcap-addr Addresses: p=0x120020014 q=0x120020014
(p==q) = true


CHERI:CHERI-O0-uintcap-offset Addresses: p=0x120020014 q=0x120020014
(p==q) = true


CHERI:CHERI-O2-uintcap-offset Addresses: p=0x120020014 q=0x120020014
(p==q) = true


CHERI:CHERI-O2-no-strict-aliasing-uintcap-offset Addresses: p=0x120020014 q=0x120020014
(p==q) = true


RV-Match Addresses: p=(nil) q=(nil)
(p==q) = true
Comparison of unspecified value:
      > in main at provenance_equality_global_xy.c:10:3

    Unspecified value or behavior (USP-CERL7):
        see C11 section 6.5.9 http://rvdoc.org/C11/6.5.9
        see MISRA-C section 8.1:3 http://rvdoc.org/MISRA-C/8.1



ch2o Fatal error: exception Main.Unknown_specifier(_)
Raised at file "map.ml", line 117, characters 16-25
Called from file "str.ml", line 253, characters 6-29


compcert-3.2 Addresses: p=0x60103c q=0x60103c
(p==q) = true


compcert-3.2-O Addresses: p=0x60103c q=0x60103c
(p==q) = true


compcert-3.2-interp Time 0: calling main()
--[step_internal_function]-->
Time 1: in function main, statement
  p = &x + 1;
  q = &y;
  printf(__stringlit_1, (void *) p, (void *) q);
  b = p == q;
  printf(__stringlit_4, b ? __stringlit_3 : __stringlit_2);
  return 0;
  return 0;
--[step_seq]-->
Time 2: in function main, statement
  p = &x + 1;
  q = &y;
  printf(__stringlit_1, (void *) p, (void *) q);
  b = p == q;
  printf(__stringlit_4, b ? __stringlit_3 : __stringlit_2);
  return 0;
--[step_seq]-->
Time 3: in function main, statement p = &x + 1;
--[step_do_1]-->
Time 4: in function main, expression p = &x + 1
--[red_var_local]-->
Time 5: in function main, expression <loc p> = &x + 1
--[red_var_global]-->
Time 6: in function main, expression <loc p> = &<loc x> + 1
--[red_addrof]-->
Time 7: in function main, expression <loc p> = <ptr x> + 1
--[red_binop]-->
Time 8: in function main, expression <loc p> = <ptr x+4>
--[red_assign]-->
Time 9: in function main, expression <ptr x+4>
--[step_do_2]-->
Time 10: in function main, statement /*skip*/;
--[step_skip_seq]-->
Time 11: in function main, statement
  q = &y;
  printf(__stringlit_1, (void *) p, (void *) q);
  b = p == q;
  printf(__stringlit_4, b ? __stringlit_3 : __stringlit_2);
  return 0;
--[step_seq]-->
Time 12: in function main, statement q = &y;
--[step_do_1]-->
Time 13: in function main, expression q = &y
--[red_var_local]-->
Time 14: in function main, expression <loc q> = &y
--[red_var_global]-->
Time 15: in function main, expression <loc q> = &<loc y>
--[red_addrof]-->
Time 16: in function main, expression <loc q> = <ptr y>
--[red_assign]-->
Time 17: in function main, expression <ptr y>
--[step_do_2]-->
Time 18: in function main, statement /*skip*/;
--[step_skip_seq]-->
Time 19: in function main, statement
  printf(__stringlit_1, (void *) p, (void *) q);
  b = p == q;
  printf(__stringlit_4, b ? __stringlit_3 : __stringlit_2);
  return 0;
--[step_seq]-->
Time 20: in function main, statement
  printf(__stringlit_1, (void *) p, (void *) q);
--[step_do_1]-->
Time 21: in function main, expression
  printf(__stringlit_1, (void *) p, (void *) q)
--[red_var_global]-->
Time 22: in function main, expression
  printf(<loc __stringlit_1>, (void *) p, (void *) q)
--[red_rvalof]-->
Time 23: in function main, expression
  printf(<ptr __stringlit_1>, (void *) p, (void *) q)
--[red_var_local]-->
Time 24: in function main, expression
  printf(<ptr __stringlit_1>, (void *) <loc p>, (void *) q)
--[red_rvalof]-->
Time 25: in function main, expression
  printf(<ptr __stringlit_1>, (void *) <ptr x+4>, (void *) q)
--[red_cast]-->
Time 26: in function main, expression
  printf(<ptr __stringlit_1>, <ptr x+4>, (void *) q)
--[red_var_local]-->
Time 27: in function main, expression
  printf(<ptr __stringlit_1>, <ptr x+4>, (void *) <loc q>)
--[red_rvalof]-->
Time 28: in function main, expression
  printf(<ptr __stringlit_1>, <ptr x+4>, (void *) <ptr y>)
--[red_cast]-->
Time 29: in function main, expression
  printf(<ptr __stringlit_1>, <ptr x+4>, <ptr y>)
Addresses: p=<57+4> q=<58+0>
Time 29: observable event:
                              extcall printf(& __stringlit_1, & x+4,
                              & y) -> 29
--[red_builtin]-->
Time 30: in function main, expression 29
--[step_do_2]-->
Time 31: in function main, statement /*skip*/;
--[step_skip_seq]-->
Time 32: in function main, statement
  b = p == q;
  printf(__stringlit_4, b ? __stringlit_3 : __stringlit_2);
  return 0;
--[step_seq]-->
Time 33: in function main, statement b = p == q;
--[step_do_1]-->
Time 34: in function main, expression b = p == q
--[red_var_local]-->
Time 35: in function main, expression <loc b> = p == q
--[red_var_local]-->
Time 36: in function main, expression <loc b> = <loc p> == q
--[red_rvalof]-->
Time 37: in function main, expression <loc b> = <ptr x+4> == q
--[red_var_local]-->
Time 38: in function main, expression <loc b> = <ptr x+4> == <loc q>
--[red_rvalof]-->
Time 39: in function main, expression <loc b> = <ptr x+4> == <ptr y>
Stuck state: in function main, expression <loc b> = <ptr x+4> == <ptr y>
Stuck subexpression: <ptr x+4> == <ptr y>
ERROR: Undefined behavior
In file included from provenance_equality_global_xy.c:1:
In file included from /usr/include/stdio.h:64:
In file included from /usr/include/_stdio.h:68:
/usr/include/sys/cdefs.h:81:2: warning: "Unsupported compiler detected" [-W#warnings]
#warning "Unsupported compiler detected"
 ^
1 warning generated.