Messages in this thread | | | Date | Fri, 1 Feb 2002 23:30:20 -0800 | From | Chris Wedgwood <> | Subject | Re: [PATCH] Re: crc32 and lib.a (was Re: [PATCH] nbd in 2.5.3 does |
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On Fri, Feb 01, 2002 at 07:01:56PM -0800, Andrew Morton wrote:
We can. Graham Stoney had all this going against 2.2. See
http://www.google.com/search?q=stoney+ffunction-sections&hl=en&start=10&sa=N http://www.cs.helsinki.fi/linux/linux-kernel/Year-2000/2000-29/0415.html
This puts every function it's own section. That seems not only cumbersome to me, but also a little complex. That said, it may be a good way if run every now and then to detect when cruft starts to accumulate for any given .config and allow people to tweak things for smaller kernels.
Is there no way to write something like:
--snip-- foo.c --snip-- void blem() { }
void bar() { blem(); return 0; }
int foo() { return 1; }
int main(...) { return foo(); } --snip-- foo.c --snip--
compile and link it, have the linker know main or some part of crt0 is special, build a graph of the final ELF object, see that bar and blem are not connected to 'main' and discard them?
I'm pretty sure (but not 100% certain) that oher compilers can do this, maybe someone can test on other platforms?
A really smart linker (if given enough compiler help) could build a directional graph and still remove this code even if blem called foo.
Perhaps I'm making something that's extremely complex sound simple, but it doesn't seem to me that this should be that complex... maybe someone more farmiliar with binutils and/or gcc can comment and tell me why I'm being a fool :)
The kernel doesn't link when you compile with -fno-inline because of all the `extern inline' qualifiers. These need to be converted to `static inline'. Jim Houston has a script which does this.
Semantically, in gcc land, someone explain the difference between:
inline
extern inline
static inline
please?
My tests seem to indicte:
inline creates an non-inline functions. Simple tests failed to have this function inlined at all
static inline and extern inline functions can and will be inlined depending on optimization level
extern inline doesn't product a non-inlined function (even if it is referenced) and hence barfs if you don't compile with optimisations for my simple test
Now, I wonder
why 'inline' for me, never inlines?
is there a way to force inlining of a function?
are non-inlined functions ever called when optimizations are enabled?
Thanks,
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