My source file contains some manipulation on struct arrays. After the initialization of some local data, there is a call to a dummy function which has its actual argument being the value of a field of one element of such an array. 

In running the executable compiled with -O, memory corruption can be observed. Note that if the call to the dummy function is removed, the generated code runs correctly.

Here is the example:

% cat tst.c
#include <stdio.h>

typedef struct {
      int re, im;
} cint32_T;

static void m_foo(int i)
{}

int main()
{
    static cint32_T sdata[3] = { { 504094, -1909779 }, { 658988, -552759 }, { -15591, -896799 } };

    cint32_T ldata[3];
    cint32_T odata[3];
    int i;

    for(i = 0; i < 3; i++) {// assign ldata from sdata
        ldata[i] = sdata[i];
    }

    for(i = 0; i < 3; i++) {// assign odata from ldata
        odata[i] = ldata[i];
    }

    m_foo(ldata[2].re);    // make a dummy call

    // Now data stored in odata[0] is corrupted.
    printf("%d, %d\n", odata[0].re, odata[0].im);

    return 0;
}


% gcc -Wall tst.c -o correct
% correct
504094, -1909779
% gcc -Wall tst.c -O -o wrong
% wrong
0, 0
%