Example: null3.c

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prev: null2.c
next: null4.c

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    #include <cheriintrin.h>
    
    #include "capprint.h"
    
    int main()
    {
        unsigned char nullrepr0[sizeof(void*)] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
        unsigned char nullrepr1[sizeof(void*)] = {0,0,0,0,0,0,0,0,5,0,1,0,0,0,0,0};
        void *p0=NULL,*p1;
    
        if(memcmp(&p0, nullrepr0, sizeof(void*))==0)
            fprintf(stderr,"NULL representation is all zeroes\n");
    
        for(unsigned int i=0;i<sizeof(void*);i++)
        {
            ((unsigned char*)&p0)[i]=nullrepr0[i];
            ((unsigned char*)&p1)[i]=nullrepr1[i];
        }
    
        if(p0==NULL) fprintf(stderr,"p0 == NULL\n");
        if(p1==NULL) fprintf(stderr,"p1 == NULL\n");
        if(p0==p1) fprintf(stderr,"p0 == p1\n");
    
        fprintf(stderr,"p0: %s, which is %s\n", null_sptr(p0), isnulls(p0));
        fprintf(stderr,"p1: %s, which is %s\n", null_sptr(p1), isnulls(p1));
    }

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 representation is all zeroes
p0 == NULL
p1 == NULL
p0 == p1
p0: 0x0 [,0x0 - 0xffffffffffffffff] (invalid), which is null
p1: 0x0 [,0x0 - 0xffffffffffffffff] (invalid), which is null
 
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
 
NULL representation is all zeroes
p0 == NULL
p1 == NULL
p0 == p1
p0: 0 [,0 - 0xffffffffffffffff] (invalid), which is null
p1: 0 [,0 - 0x20000000] (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
 
NULL representation is all zeroes
p0 == NULL
p1 == NULL
p0 == p1
p0: 0 [,0 - 0xffffffffffffffff] (invalid), which is null
p1: 0 [,0 - 0xffffffffffffffff] (invalid), which is null
 
gcc-morello-O0
gcc-morello-O3
 
NULL representation is all zeroes
p0 == NULL
p1 == NULL
p0 == p1
p0: 0x0 [,0x0-0xffffffffffffffff] (invalid), which is null
p1: 0x0 [,0x0-0xffffffffffffffff] (invalid), which is null