building kernel with -O

[Valdis.Kletnieks at vt.edu]

On Wed, 30 Jul 2014 09:03:38 -0500, Xin Tong said:

> Ive heard that one can not build the entire Linux kernel with -O0 option.
> why is that ? being a compiler developer, i can not think of reasons why
> that is the case.

The short answer:  -O0 completely suppresses function inlining, and there
are several places where the kernel depends on inlining for correct
operation (most notably with things like __builtin_return_address()
and friends for introspecting the stack, but there's a few other
corner cases I can't remember at the moment...)
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