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 %
Works on all active release branches.
Confirmed with 4.2.4 btw.