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Cog segfaults on linux

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Eliot Miranda-2

Cog segfaults on linux

Hi All,

today I noticed that the default stack alignment for Cog on linux is only 4 bytes. On Mac OS X x86 it has always been 16 bytes to support SSE 64-bit and 128-bit instructions. I wonder whether this might be anything to do with the random crashes people have seen running Cog on linux. If you have seen random crashes perhaps you could recompile using the attached version of platforms/Cross/vm/sqCogStackAlignment.h and report back. You'll have to do a make reallyclean and repeat the configure command to recompile everything (ok you can also say rm */*o */*a */.libs/*).

best

Eliot

sqCogStackAlignment.h (2K) Download Attachment

johnmci

Re: Cog segfaults on linux

Ah, in the macintosh FFI stuff I have...

subl %ecx, %esp

and $0xFFFFFFF0,%esp /*align to 128-bits*/

What is a killer is that some quicktime API calls *assume* gee we KNOW there is like 4 bytes up there on the stack that isn't used because of the alignment so we'll just STUFF some bytes up there to

save time and energy...

Also see http://developer.apple.com/mac/library/documentation/DeveloperTools/Conceptual/LowLevelABI/130-IA-32_Function_Calling_Conventions/IA32.html#//apple_ref/doc/uid/TP40002492-SW4

*Cough* obviously forgoing this causes interesting side effects.

On 2010-07-14, at 6:58 PM, Eliot Miranda wrote:

Hi All,

today I noticed that the default stack alignment for Cog on linux is only 4 bytes. On Mac OS X x86 it has always been 16 bytes to support SSE 64-bit and 128-bit instructions. I wonder whether this might be anything to do with the random crashes people have seen running Cog on linux. If you have seen random crashes perhaps you could recompile using the attached version of platforms/Cross/vm/sqCogStackAlignment.h and report back. You'll have to do a make reallyclean and repeat the configure command to recompile everything (ok you can also say rm */*o */*a */.libs/*).

best
Eliot

<sqCogStackAlignment.h>

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Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com

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