ASLR incompatibility with Cygwin binaries

[Lee]

On Fri, Jul 10, 2026 at 8:31 AM Nikhil Sabharwal via Cygwin
<cygwin@cygwin.com> wrote:
>
> To the developers & maintainers of cygwin
>
> I wanted to reach out regarding Cygwin and its compatibility with Windows exploit protection mechanisms, specifically ASLR. My current understanding is that MSYS2 has difficulties supporting this feature due to limitations inherited from Cygwin. Certain functionality within the compatibility layer appears to rely on a fixed address layout, causing binaries with ASLR enabled to fail with error messages such as:
>
> *** fatal error - cygheap base mismatch detected - 0xD5F410/0xE9F410
> These are the results I observe when running binaries built with the DYNAMICBASE flag enabled.

This seems to work around the problem.  Note: I copied the solution
from stackoverflow with no real understanding on my part, so I can't
explain what's going on

LDFLAGS="${LDFLAGS} -Wl,--dynamicbase,--export-all-symbols"
# https://en.wikipedia.org/wiki/Address_space_layout_randomization
# https://stackoverflow.com/questions/24283918/how-can-i-enable-aslr-dep-and-safeseh-on-an-exe-in-codeblocks-using-mingw
#   ASLR with gcc has a problem: -Wl,--dynamicbase doesn't emit the
necessary relocation table.
#   As a workaround, you can pass -Wl,--dynamicbase,--export-all-symbols
#   NOTE: you can't have both this and profiling (cflags='-pg') enabled!

Regards,
Lee