Nikos Chantziaras wrote:
On 08/15/2009 03:33 AM, [email protected] wrote:
[...] This being 4.3.4 to 4.1.1 looks like a major version change
according to the upgrade guide. It doesn't mention what a switch
manual takes, but it does list a whole series of steps such as
remerging system and world without saying exactly when they or how
much are necessary. I'd just as soon not do that unless necessary,
but I'd much more regret not doing it if I should have.
Switching the compiler with gcc-config is enough with this update.
There are no ABI changes and packages built with GCC 4.3 will happily
work together with the ones build with 4.4.
I am doing an emerge -e system and emerge -e world anyway though
since I want to take advantage of the faster code 4.4 produces in
general, but also more specific whether or not the new "graphite"
optimizer of GCC 4.4 (needs "graphite" USE flag enabled for gcc) will
give additional performance gain.
(If anyone is interested in that, you need to first add:
-floop-interchange -floop-strip-mine -floop-block
to CFLAGS/CXXFLAGS (the options enabling the Graphite optimizer) and
then "emerge -e" system and world.)
Thanks for the information.
1. FWIW, I found the following note:
"To use this code transformation, GCC has to be configured with
--with-ppl and --with-cloog to enable the Graphite loop transformation
infrastructure."
on the following page:
<http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Optimize-Options.html#Optimize-Options>
2. Also FWIW, I found the following note:
* GCC can now emit code for protecting applications from
stack-smashing attacks. The protection is realized by buffer overflow
detection and reordering of stack variables to avoid pointer corruption.
* Some built-in functions have been fortified to protect them
against various buffer overflow (and format string) vulnerabilities.
Compared to the mudflap bounds checking feature, the safe builtins have
far smaller overhead. This means that programs built using safe builtins
should not experience any measurable slowdown.
on the following page: <http://gcc.gnu.org/gcc-4.1/changes.html>
which suggests to me that the mudflap option should be disabled before
emerging world
HTH
