align-test-dynamic.c

 cat align-test.c 

#include <stdlib.h>

/* from include/my_compiler.h */

#if defined __GNUC__ || defined __SUNPRO_C || defined __SUNPRO_CC
/* Specifies the minimum alignment of a type. */
# define MY_ALIGNOF(type)   __alignof__(type)
/* Determine the alignment requirement of a type. */
# define MY_ALIGNED(n)      __attribute__((__aligned__((n))))
/* Microsoft Visual C++ */
#elif defined _MSC_VER
# define MY_ALIGNOF(type)   __alignof(type)
# define MY_ALIGNED(n)      __declspec(align(n))
#else /* Make sure they are defined for other compilers. */
# define MY_ALIGNOF(type)
# define MY_ALIGNED(size)
#endif

#ifndef CPU_LEVEL1_DCACHE_LINESIZE
  #if defined(__s390__)
    #define CPU_LEVEL1_DCACHE_LINESIZE 256
  #elif defined(__powerpc__) || defined(__aarch64__)
    #define CPU_LEVEL1_DCACHE_LINESIZE 128
  #else
    #define CPU_LEVEL1_DCACHE_LINESIZE 64
  #endif
#endif

struct s_one {
        char first[30] MY_ALIGNED(CPU_LEVEL1_DCACHE_LINESIZE);
};

struct s_multiple {
        char first;
        unsigned long two;
        char three;
        char four[40] MY_ALIGNED(CPU_LEVEL1_DCACHE_LINESIZE);
        char last;
};

struct s_one one_arr[2];

struct s_multiple multiple_arr[2];

struct s_simple {
        char first[30];
};

struct s_simple simple_arr[2];

#include <stdio.h>
#include <stddef.h>

int main()
{
        printf("Alignment %x\n\n", CPU_LEVEL1_DCACHE_LINESIZE);

        printf("sizeof(one) %zx\n", sizeof(struct s_one));
        printf("one[0] %p\n", &one_arr[0].first);
        printf("one[1] %p\n", &one_arr[1].first);
        printf("one ptrdiff %tx\n", (ptrdiff_t) (&one_arr[1].first - &one_arr[0].first));

        printf("\nsizeof(multiple) %zx\n", sizeof(struct s_multiple));
        printf("multiple[0].first %p\n", &multiple_arr[0].first);
        printf("multiple[0].four %p\n",  &multiple_arr[0].four);
        printf("multiple[1].first %p\n", &multiple_arr[1].first);
        printf("multiple diff %tx\n", (ptrdiff_t) (&multiple_arr[1].first - &multiple_arr[0].first));

        printf("\nsizeof(simple) %zx\n", sizeof(struct s_simple));
        printf("simple[0] %p\n", &simple_arr[0].first);
        printf("simple[1] %p\n", &simple_arr[1].first);
        printf("simple diff %tx\n", (ptrdiff_t) (&simple_arr[1].first - &simple_arr[0].first));

        struct s_multiple *dmultiple_arr, *d2multiple_arr;
        dmultiple_arr=malloc(sizeof(struct s_multiple)*2);

        printf("\ndmultiple[0].first %p\n", &dmultiple_arr[0].first);
        printf("dmultiple[0].four %p\n",  &dmultiple_arr[0].four);
        printf("dmultiple[1].first %p\n", &dmultiple_arr[1].first);
        printf("dmultiple[1].last %p\n", &dmultiple_arr[1].last);
        printf("dmultiple diff %tx\n", (ptrdiff_t) (&dmultiple_arr[1].first - &dmultiple_arr[0].first));

        d2multiple_arr=malloc(sizeof(struct s_multiple)*2);

        printf("\nd2multiple[0].first %p\n", &d2multiple_arr[0].first);
        printf("d2multiple[0].four %p\n",  &d2multiple_arr[0].four);
        printf("d2multiple[1].first %p\n", &d2multiple_arr[1].first);
        printf("d2multiple diff %tx\n", (ptrdiff_t) (&d2multiple_arr[1].first - &d2multiple_arr[0].first));


        printf("\nd2multiple.first - dmultiple.last diff %tx\n", (ptrdiff_t) (&d2multiple_arr[1].first - &dmultiple_arr[0].last));
        free(dmultiple_arr);
        free(d2multiple_arr);
}


uname -m
x86_64

 gcc -o align-test align-test.c  && ./align-test
Alignment 40

sizeof(one) 40
one[0] 0x6011c0
one[1] 0x601200
one ptrdiff 2

sizeof(multiple) 80
multiple[0].first 0x6010c0
multiple[0].four 0x601100
multiple[1].first 0x601140
multiple diff 80

sizeof(simple) 1e
simple[0] 0x601080
simple[1] 0x60109e
simple diff 1

dmultiple[0].first 0x104b420
dmultiple[0].four 0x104b460
dmultiple[1].first 0x104b4a0
dmultiple[1].last 0x104b508
dmultiple diff 80

d2multiple[0].first 0x104b530
d2multiple[0].four 0x104b570
d2multiple[1].first 0x104b5b0
d2multiple diff 80

d2multiple.first - dmultiple.last diff 128

   gcc -o align-test align-test.c -ljemalloc  && ./align-test
Alignment 40

sizeof(one) 40
one[0] 0x6011c0
one[1] 0x601200
one ptrdiff 2

sizeof(multiple) 80
multiple[0].first 0x6010c0
multiple[0].four 0x601100
multiple[1].first 0x601140
multiple diff 80

sizeof(simple) 1e
simple[0] 0x601080
simple[1] 0x60109e
simple diff 1

dmultiple[0].first 0x7f1b5a819000
dmultiple[0].four 0x7f1b5a819040
dmultiple[1].first 0x7f1b5a819080
dmultiple[1].last 0x7f1b5a8190e8
dmultiple diff 80

d2multiple[0].first 0x7f1b5a819100
d2multiple[0].four 0x7f1b5a819140
d2multiple[1].first 0x7f1b5a819180
d2multiple diff 80

d2multiple.first - dmultiple.last diff 118
  
  
  ppc64le
  
gcc -o align-test align-test.c  && ./align-test
Alignment 80

sizeof(one) 80
one[0] 0x10020380
one[1] 0x10020400
one ptrdiff 4

sizeof(multiple) 100
multiple[0].first 0x10020180
multiple[0].four 0x10020200
multiple[1].first 0x10020280
multiple diff 100

sizeof(simple) 1e
simple[0] 0x10020100
simple[1] 0x1002011e
simple diff 1

dmultiple[0].first 0x1001a310420
dmultiple[0].four 0x1001a3104a0
dmultiple[1].first 0x1001a310520
dmultiple[1].last 0x1001a3105c8
dmultiple diff 100

d2multiple[0].first 0x1001a310630
d2multiple[0].four 0x1001a3106b0
d2multiple[1].first 0x1001a310730
d2multiple diff 100

d2multiple.first - dmultiple.last diff 268

  gcc -o align-test align-test.c -ljemalloc  && ./align-test
Alignment 40

sizeof(one) 40
one[0] 0x6011c0
one[1] 0x601200
one ptrdiff 2

sizeof(multiple) 80
multiple[0].first 0x6010c0
multiple[0].four 0x601100
multiple[1].first 0x601140
multiple diff 80

sizeof(simple) 1e
simple[0] 0x601080
simple[1] 0x60109e
simple diff 1

dmultiple[0].first 0x7f1b5a819000
dmultiple[0].four 0x7f1b5a819040
dmultiple[1].first 0x7f1b5a819080
dmultiple[1].last 0x7f1b5a8190e8
dmultiple diff 80

d2multiple[0].first 0x7f1b5a819100
d2multiple[0].four 0x7f1b5a819140
d2multiple[1].first 0x7f1b5a819180
d2multiple diff 80

d2multiple.first - dmultiple.last diff 118