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[Bug c/22278] gcc -O2 discards cast to volatile
- From: "gcc2eran at tromer dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 2 Jul 2005 22:07:48 -0000
- Subject: [Bug c/22278] gcc -O2 discards cast to volatile
- References: <20050702164323.22278.olivier.baudron@m4x.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From gcc2eran at tromer dot org 2005-07-02 22:07 -------
Prior versions of gcc did "respect" casts to pointer-to-volatile and did not
optimize away the access. I've seen a lot of code that relies on that, and which
would thus be broken by gcc 4.x (in a subtle and hard-to-debug way). One recent
example is an elusive bug in Fedora Core 4's X.org package which bit many users
(https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=161242).
I can't imagine a programmer casting into a pointer to volatile without really
meaning it, so if the behavior is not defined by the standard then both
compatibility and the principle of least astonishment seem to suggest reverting
to the old behavior.
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What |Removed |Added
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CC| |gcc2eran at tromer dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22278