Statically linking musl with lto optimizations

Statically linking musl with lto optimizations

[Chris Anderson]

Hi

I just wanted to know if anyone has tried this and if so with what success? 

I have tried adding the -flto and -fuse-linker-plugin to my CFLAGS but when I go and link against the static lib/libc.a archive I get a lot of unresolved symbols. I fixed this by changing the makefile thus:

 38 AR      = $(CROSS_COMPILE)gcc-ar
 39 RANLIB  = $(CROSS_COMPILE)gcc-ranlib

which is described in this thread http://permalink.gmane.org/gmane.comp.gcc.patches/221033

This meant that the archive was being created correctly.

The problem that I now have is that if I use
If I use ./bin/musl-gcc  -flto=5 -fuse-linker-plugin -o test test.c I get a whole lot of unresolved symbols being spewed out by the linker.

If I try and link using gcc without gcc libs and but without the musl spec file, ie gcc   -flto=5 -fuse-linker-plugin -static -nostdlib all is good apart from an undefined reference to __dynlink.

If I add a dummy __dynlink then the whole program links of course it wont execute because the .bss and other segments are not configured.

What is the correct way to do this?

Cheers

Chris

Re: Statically linking musl with lto optimizations

[Szabolcs Nagy]

* Chris Anderson <cjanderson@yandex.com> [2014-01-28 01:52:46 +0000]:
> I just wanted to know if anyone has tried this and if so with what success? 

i think it was tried before

my native toolchain cannot do lto but i tried musl-cross and it seems
to work without any tricks:

tar xJf crossx86-i486-linux-musl-0.9.15.tar.xz
git clone git://git.musl-libc.org/musl
cd musl

# usig `pwd` to make install a nop
# cross compilation disables the wrapper, but i want to use it
./configure CROSS_COMPILE=../i486-linux-musl/bin/i486-linux-musl- CFLAGS=-flto --syslibdir=`pwd`/lib --prefix=`pwd` --disable-shared --enable-gcc-wrapper
make
make install

cat >t.c <<EOF
#include <stdio.h>
int main() {printf("hello\n");}
EOF

# -static is not needed, we only built libc.a
REALGCC=../i486-linux-musl/bin/i486-linux-musl-gcc tools/musl-gcc -static -flto t.c
./a.out

> I have tried adding the -flto and -fuse-linker-plugin to my CFLAGS but when I go and link against the static lib/libc.a archive I get a lot of unresolved symbols. I fixed this by changing the makefile thus:
> 
>  38 AR      = $(CROSS_COMPILE)gcc-ar
>  39 RANLIB  = $(CROSS_COMPILE)gcc-ranlib
> 
> which is described in this thread http://permalink.gmane.org/gmane.comp.gcc.patches/221033

i think you only need this if binutils was built without plugin support

> This meant that the archive was being created correctly.
> 
> The problem that I now have is that if I use
> If I use ./bin/musl-gcc  -flto=5 -fuse-linker-plugin -o test test.c I get a whole lot of unresolved symbols being spewed out by the linker.
> 
> If I try and link using gcc without gcc libs and but without the musl spec file, ie gcc   -flto=5 -fuse-linker-plugin -static -nostdlib all is good apart from an undefined reference to __dynlink.
> 

if you use -nostdlib you need to do more work
(provide the musl crt*.o and libgcc the way the spec file describes)

(you are linking the _start symbol of the loader now, libc.so has
its own _start so you can execute it as a loader, if you correctly
specify the crt*o files then your app gets the right _start that
does not reference __dynlink)