[Bug libc/10776] New: With M_MMAP_MAX=0 free() causes undefined behaviour.

["Christian dot Meier at informatik dot stud dot uni-erlangen dot de" <sourceware-bugzilla at sourceware dot org>]

Calling the following at the beginning of main causes an application (with many
allocations) to behave undefined.

if (mlockall(MCL_CRRENT|MCL_FUTURE))
  return 1;

mallopt(M_TRIM_THRESHOLD, -1);
mallopt(M_MMAP_MAX, 0);
int * buffer = (int*) malloc(10*1024*1024);

if (!buffer)
  return 1;

for (int i = 0; i < 10*1024*1024/sizeof(int); ++i) {
  buffer[i] = 42;
}
free(buffer);

However, commenting out either free(buffer); or mallopt(M_MAP_MAX, 0); causes
the application to behave as expected.

-- 
           Summary: With M_MMAP_MAX=0 free() causes undefined behaviour.
           Product: glibc
           Version: 2.10
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: Christian dot Meier at informatik dot stud dot uni-
                    erlangen dot de
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10776

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