stringtest to check the optimisation of constant substrings

logfile

[bebe:~/stringtest] % gcc --version
gcc (GCC) 8.2.1 20180831
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
[bebe:~/stringtest] % gcc -o stringtest stringtest.c -O0
[bebe:~/stringtest] % ./stringtest
sameptr: (diff: 0)
        same1: 0x563efba8d004
        same2: 0x563efba8d004
abptr: (diff: -5)
        a: 0x563efba8d037
        b: 0x563efba8d03c
digsptr: (diff: -5)
        digs1: 0x563efba8d066
        digs2: 0x563efba8d06b
[bebe:~/stringtest] % gcc -o stringtest stringtest.c -O1
[bebe:~/stringtest] % ./stringtest
sameptr: (diff: 0)
        same1: 0x55ebae94101a
        same2: 0x55ebae94101a
abptr: (diff: 1)
        a: 0x55ebae941038
        b: 0x55ebae941037
digsptr: (diff: -1)
        digs1: 0x55ebae941061
        digs2: 0x55ebae941062
[bebe:~/stringtest] % gcc -o stringtest stringtest.c -O2
[bebe:~/stringtest] % ./stringtest
sameptr: (diff: 0)
        same1: 0x556c9d83601a
        same2: 0x556c9d83601a
abptr: (diff: 1)
        a: 0x556c9d836038
        b: 0x556c9d836037
digsptr: (diff: -1)
        digs1: 0x556c9d836061
        digs2: 0x556c9d836062
[bebe:~/stringtest] % gcc -o stringtest stringtest.c -O3
[bebe:~/stringtest] % ./stringtest
sameptr: (diff: 0)
        same1: 0x55dc269a301a
        same2: 0x55dc269a301a
abptr: (diff: 1)
        a: 0x55dc269a3038
        b: 0x55dc269a3037
digsptr: (diff: -1)
        digs1: 0x55dc269a3061
        digs2: 0x55dc269a3062
[bebe:~/stringtest] % gcc -o stringtest stringtest.c -Os
[bebe:~/stringtest] % ./stringtest
sameptr: (diff: 0)
        same1: 0x55d7f292f01a
        same2: 0x55d7f292f01a
abptr: (diff: 1)
        a: 0x55d7f292f038
        b: 0x55d7f292f037
digsptr: (diff: -1)
        digs1: 0x55d7f292f061
        digs2: 0x55d7f292f062

stringtest.c

#include <stdio.h>

int main(int argc, char *argv[])
{
        const char *same1 = "same";
        const char *same2 = "same";
        printf("sameptr:\n");
        printf("\tsame1: %p\n", (void*)same1);
        printf("\tsame2: %p\n", (void*)same2);


        const char *a =  "asdf";
        const char *b = "basdf";
        printf("abptr:\n");
        printf("\ta: %p\n", (void*)a);
        printf("\tb: %p\n", (void*)b);

        const char *digs1 = "1234";
        const char *digs2 =  "234";
        printf("digsptr:\n");
        printf("\tdigs1: %p\n", (void*)digs1);
        printf("\tdigs2: %p\n", (void*)digs2);

        return 0;
}