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From: Patrick Herbst <paherbst@gmail.com>
Date: Sun, 29 Jan 2023 18:05:14 -0500
Message-ID: <CACMdL5JQAf07dknwFq9DrQn_7rw-i-Z7PnOJ1H59fURe+jQnGw@mail.gmail.com>
Subject: Optimization auto-setting _FORTIFY_SOURCE ??
To: gcc-help <gcc-help@gcc.gnu.org>
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Using GCC 9.4, I've noticed setting -O1 will set
_FORTIFY_SOURCE=2

I'm able to see this by running
gcc -c -E -dM -O1 - < /dev/null | grep FORTIFY_SOURCE

But running the same command without -O1 doesn't set it.

Is this documented?  is this expected behavior?  I could not find any
reference to how optimization leads to setting this macro.

Any tips on where I can look, or what i'm missing to see this connection?

Thanks!