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Date: Wed, 13 May 2015 19:36:46 +0200
From: Alex Dowad <alexinbeijing@...il.com>
To: musl@...ts.openwall.com
Subject: Re: [PATCH v2] First prototype of script which adds CFI directives
to x86 asm
Thanks to Szabolcs Nagy for your reply!
> it might make sense to have a make rule that produces the cfi asm for inspection
Any opinions from others on this?
> i wonder if a configure check for .cfi support should be added: in theory
> an assembler may not support it (tcc?)
Sure, I can do this. If debugging is not enabled, it doesn't make much sense
to use the CFI script either.
Would adding another variable to config.mak, something like GENERATE_CFI=yes
(or something like that) be acceptable?
> move this loop to BEGIN so it only runs at startup
I tried benchmarking and there is no measurable impact on performance either way.
I would prefer to leave the loop where it is, to make the script easier to read
(keeping related code together).
I added 'i' to the argument list to make it local -- thanks for the tip.
> i think hex conversion for $123 is wrong in i386 asm
Fixed in the v2.
> allow whitespace between ',' and the regs
Fixed, thanks.
> (missing .cfi_startproc/endproc might be problematic i think
> because .cfi directives can be rejected outside of startproc/endproc)
Yes, that's why the script doesn't emit them unless it is inside a startproc/endproc pair.
Regarding the concern with .type @function, I am trying a different strategy now
for identifying the beginning and end of functions. Please see the v3 (soon to be
posted).
Thanks,
Alex
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