optimization in kernel compile

[ishare]

On Fri, Mar 22, 2013 at 09:55:53AM -0400, Valdis.Kletnieks at vt.edu wrote:
> On Fri, 22 Mar 2013 13:41:25 +0800, ishare said:
> >   Is it  needed or must to compile fs and driver with -O2 option when compiling kernel ?
> 
> It's not strictly mandatory to use -O2 (for a while, -Os was the default). There
> are a few places that for correctness, you *cannot* use -O0. For instance, a
> few places where we use builtin_return_address() inside an inline (-O0
> won't inline so builtin_return_address() ends up returning a pointer to
> a function when we want the function's parent).
 
  So it will cause an error ?
> 
> Since gdb and friends are able to deal with -O2 compiled code just fine,
> there's really no reason *not* to optimize the kernel.

  the debug information will be stripped  by  -O2 ,for example ,you can not touch 
  the value of  some varibles at stack , and debugging will not run line by line,
  instead , the source jump in unexpectable order .