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Subject: Re: Optimization auto-setting _FORTIFY_SOURCE ??
From: Xi Ruoyao <xry111@xry111.site>
To: Patrick Herbst <paherbst@gmail.com>
Cc: gcc-help <gcc-help@gcc.gnu.org>
Date: Mon, 30 Jan 2023 12:23:57 +0800
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On Sun, 2023-01-29 at 18:05 -0500, Patrick Herbst via Gcc-help wrote:
> Using GCC 9.4, I've noticed setting -O1 will set
> _FORTIFY_SOURCE=3D2
>=20
> I'm able to see this by running
> gcc -c -E -dM -O1 - < /dev/null | grep FORTIFY_SOURCE
>=20
> But running the same command without -O1 doesn't set it.
>=20
> Is this documented?=C2=A0 is this expected behavior?=C2=A0 I could not fi=
nd any
> reference to how optimization leads to setting this macro.
>=20
> Any tips on where I can look, or what i'm missing to see this
> connection?

It's because your distro hacked GCC code to define _FORTIFY_SOURCE when
optimization is enabled.  Vanilla GCC does not have this behavior.


--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University