Example: null2.c

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    #include <stdint.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <limits.h>
    
    #include "capprint.h"
    
    int main()
    {
        // C0
        int *p = NULL;
        fprintf(stderr,"NULL: %s, which is %s\n", null_sptr(p), isnulls(p));
    
        // as intptr_t
        intptr_t ip = (intptr_t)p;
        fprintf(stderr,"NULL as intptr_t: %s\n", null_siptr(ip));
        fprintf(stderr,"NULL as intptr_t cast to long: %ld\n", (long)ip);
    
        // assigning runtime 0 value to pointer
        long x = 99;
        p = (int*)(x-99);
        fprintf(stderr,"assigned: %s, which is %s\n", null_sptr(p), isnulls(p));
    }

Experimental data (what does this mean?)

cerberus-cheri
cerberus-cheri-no-pnvi
cerberus-cheri-revocation
cerberus-cheri-revocation-no-pnvi
cerberus-cheri-cornucopia
cerberus-cheri-cornucopia-no-pnvi
 
NULL: 0x0 [,0x0 - 0xffffffffffffffff] (invalid), which is null
NULL as intptr_t: 0x0 [,0x0 - 0xffffffffffffffff] (invalid)
NULL as intptr_t cast to long: 0
assigned: 0x0 [,0x0 - 0xffffffffffffffff] (invalid), which is null
 
clang-morello-O0-bounds-conservative
clang-morello-O3-bounds-conservative
clang-morello-O0-bounds-references-only
clang-morello-O0-bounds-subobject-safe
clang-morello-O3-bounds-subobject-safe
clang-morello-O0-bounds-aggressive
clang-morello-O0-bounds-very-aggressive
clang-morello-O0-bounds-everywhere-unsafe
clang-riscv-O0-bounds-conservative
clang-riscv-O3-bounds-conservative
clang-riscv-O0-bounds-references-only
clang-riscv-O0-bounds-subobject-safe
clang-riscv-O3-bounds-subobject-safe
clang-riscv-O0-bounds-aggressive
clang-riscv-O0-bounds-very-aggressive
clang-riscv-O0-bounds-everywhere-unsafe
 
tests/cheri/null2.c:21:9: warning: cast from provenance-free integer type to pointer type will give pointer that can not be dereferenced [-Wcheri-capability-misuse]
    p = (int*)(x-99);
        ^
1 warning generated.
NULL: 0 [,0 - 0xffffffffffffffff] (invalid), which is null
NULL as intptr_t: 0 [,0 - 0xffffffffffffffff] (invalid)
NULL as intptr_t cast to long: 0
assigned: 0 [,0 - 0xffffffffffffffff] (invalid), which is null
 
gcc-morello-O0
gcc-morello-O3
 
tests/cheri/null2.c: In function 'main':
tests/cheri/null2.c:21:9: warning: cast from provenance-free integer type to pointer type will give pointer that can not be dereferenced [-Wcheri-capability-misuse]
   21 |     p = (int*)(x-99);
      |         ^
tests/cheri/null2.c:21:9: note: insert cast to intptr_t to silence this warning
NULL: 0x0 [,0x0-0xffffffffffffffff] (invalid), which is null
NULL as intptr_t: 0x0 [,0x0-0xffffffffffffffff] (invalid)
NULL as intptr_t cast to long: 0
assigned: 0x0 [,0x0-0xffffffffffffffff] (invalid), which is null