Re: [Qemu-devel] [PATCH v6 3/8] Makefile: introduce common-obj-m and block-obj-m for DSO

[Peter Maydell]

On 11 September 2013 14:34, Fam Zheng <address@hidden> wrote:
> Add necessary rules and flags for shared object generation.
> $(common-obj-m) will include $(block-obj-m), like $(common-obj-y) does
> for $(block-obj-y). The new rules introduced here are:
>
> 0) For all %.so compiling:
>
>     QEMU_CFLAGS += -fPIC
>
> 1) %.o in $(common-obj-m) is compiled to %.o, then linked to %.so.
>
> 2) %.mo in $(common-obj-m) is the placeholder for %.so for pattern
> matching in Makefile. It's linked to "-shared" with all its dependencies
> (multiple *.o) as input. Which means the list of depended objects must
> be ruled out in each sub-Makefile.objs with an variable:
>
>     foo.mo-objs := bar.o baz.o qux.o
>
> in the same style with foo.o-cflags and foo.o-libs.

This spectacularly breaks compilation if you don't have libtool
(which is currently an entirely optional dependency).

Test build/configure command, for x86-64 linux:

rm -rf build/x86 && mkdir build/x86 && (cd build/x86 && LIBTOOL=
../../configure --target-list=arm-softmmu --enable-debug --cc='ccache
gcc' --disable-smartcard-nss) && make -C build/x86 -j4

Fails like this:

  LINK  qemu-ga
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 0 has invalid symbol index 10
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 1 has invalid symbol index 11
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 2 has invalid symbol index 2
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 3 has invalid symbol index 2
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 4 has invalid symbol index 10
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 5 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 6 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 7 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 8 has invalid symbol index 2
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 9 has invalid symbol index 2
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 10 has invalid symbol index 11
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 11 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 12 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 13 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 14 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 15 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 16 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 17 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 18 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 19 has invalid symbol index 12
/usr/bin/ld.bfd.real:
/usr/lib/debug/usr/lib/x86_64-linux-gnu/Scrt1.o(.debug_info):
relocation 20 has invalid symbol index 20
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/Scrt1.o:
In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
make: *** [qemu-ga] Error 1


If we make libtool mandatory then (a) we need to make configure
bail out if it can't find it (b) we need to flag it up in the release notes
as a new mandatory dependency.

I'd really prefer it if we could avoid it though; among other things
MacOSX doesn't ship with a GNU libtool.

-- PMM