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You may aware or not that there is a nice optimization (more effective |
| 2 |
if you have some registers to spare) based on how you access memory |
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thought variables. Since it wasn't that effective and didn't break |
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anything it is enabled since -O2. |
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|
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Problem: recent gcc are doing some quite smart tricks with aliasing and |
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as result they will break in subtle way your code if you use |
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strict-aliasing rules optimization on type puns. |
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|
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Quick solution: enforce -fno-strict-aliasing as global cflag. |
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Side effect: you may lose a bit in performance, but better safe than |
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sorry: the first package showing issues was openssl[1] mismatching |
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hashes, guess how discovered that and how (hint: ssh was refusing logins...) |
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Long term solution: |
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1- check your new package for aliasing compliance, and if you have time |
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fix it in the code or in the makefile, if you haven't append |
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-fno-strict-aliasing to the cflags and maybe send a notice about it upstream |
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2- append -fno-strict-aliasing to every source known to have such issue. |
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I'll do 2 on all packages in the tree showing the issue if you think is |
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ok, arches not yet affected will be in the future. |
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lu |
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[1]http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14725 |
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-- |
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|
| 33 |
Luca Barbato |
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|
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Gentoo/linux Gentoo/PPC |
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http://dev.gentoo.org/~lu_zero |
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|
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-- |
| 39 |
gentoo-dev@g.o mailing list |
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