[Python-Dev] ANSI strict aliasing and Python

Andrew MacIntyre andymac@bullseye.apana.org.au
Sat, 19 Jul 2003 09:57:04 +1000 (EST)

On Fri, 18 Jul 2003, Tim Peters wrote:

> Has anyone tried running Python compiled without no-strict-aliasing?  If so,
> how bad was it?

I've never used no-strict-aliasing with gcc on the EMX port.  With gcc
2.8.1 and 2.95.2 -O3, I've not seen failures that appear to be bad code;
with gcc 3.2.1 I see 3 tests (test_codeccallbacks, test_format &
test_unicode) that seem to have repeatable failures that are sensitive to
optimisation level (-O3 = fail, -O2 = pass) which may be bad code.  I'll
try -no-stict-aliasing when I get back digging into this.

BTW, the following sequence of tests causes a core dump from an assertion
failure in test_enumerate on EMX which I haven't been able to replicate on
FreeBSD :-(


I haven't played with all possible permutations, but skipping any one of
the precursor tests doesn't exhibit the assertion failure, which is:

Assertion failed: gc->gc.gc_refs != 0, file ../../Modules/gcmodule.c, line

I also encountered a hang in test_poll on FreeBSD 5.1 (gcc 3.2.2), which I
suspect is more likely to be a problem with FreeBSD 5.1's library code
(thread codebase instability) than Python.  I ran about a dozen full -r
runs on FreeBSD 4.8 (gcc 2.95.4) with no sign of anything being amiss
(which doesn't mean it isn't, just not readily tripped over).

More digging clearly indicated on both EMX issues...

Andrew I MacIntyre                     "These thoughts are mine alone..."
E-mail: andymac@bullseye.apana.org.au  (pref) | Snail: PO Box 370
        andymac@pcug.org.au             (alt) |        Belconnen  ACT  2616
Web:    http://www.andymac.org/               |        Australia