[issue24851] infinite loop in faulthandler._stack_overflow

[Paul Murphy]

New submission from Paul Murphy:

This is a duplicate of Issue 23654, except it occurs on GCC 5.1 with -O2 when 
building for a ppc64le target.

GCC is optimizes this as a tail call, removing the accesses to the "unused" 
stack variables.

--
components: Extension Modules
files: fix_stack_overflow.patch
keywords: patch
messages: 248472
nosy: Paul Murphy
priority: normal
severity: normal
status: open
title: infinite loop in faulthandler._stack_overflow
versions: Python 3.4
Added file: http://bugs.python.org/file40170/fix_stack_overflow.patch

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[issue24851] infinite loop in faulthandler._stack_overflow

[Paul Murphy]

Paul Murphy added the comment:

Somehow, you need to preserve access to the stack memory. The generated code is 
still growing the stack, it just fails to touch any of it.

I'm guessing a volatile access would just add an extra non-stack access to the 
infinite loop.

Initially, I had tried creating a non-inlined function to touch the stack 
memory. It worked in this case, but still required some undesirable compiler 
specific assistance.

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[issue24851] infinite loop in faulthandler._stack_overflow

[Paul Murphy]

Paul Murphy added the comment:

...
#pragma GCC optimize ("no-optimize-sibling-calls")
...

Does preserve the desired behavior under -O2 and -O3, probably a bit nicer than 
using O0.

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