RE: how to include out of tree source during the qemu build? ==> undefined reference to symbol 'dlsym@@GLIBC_2.2.5'

[ckim]

Hi, all,

I added --extra-ldflags=-ldl (and --extra-cflags options which I need) during 
the configuration and can see QEMU_LDFLAGS now contain -ldl during the make.
But I still see this error below(make run under build directory, this is 
qemu-5.1.0).
(The source code hw/misc/axpu_if.c contains #include <dlfcn.h> line. )

/usr/bin/ld: ../hw/misc/axpu_if.o: undefined reference to symbol 
'dlsym@@GLIBC_2.2.5'
/usr/bin/ld: 
/usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libdl.so: error 
adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:219: qemu-system-aarch64] Error 1
make: *** [Makefile:527: aarch64-softmmu/all] Error 2

To see my glibc version, I tried this,

ckim@ckim-ubuntu:~/xxx/qemu-5.1.0/build$ ldd --version
ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Written by Roland McGrath and Ulrich Drepper.

The corresponding code (using dlopen and dlsym) can be compiled ok in my system 
when run separately so I don't think I should install lower version of glibc.
I don't know what to try. Has anybody any suggestion?
Thanks!
Chan Kim

> -----Original Message-----
> From: Peter Maydell <peter.maydell@linaro.org>
> Sent: Thursday, May 20, 2021 6:10 PM
> To: Chan Kim <ckim@etri.re.kr>
> Cc: qemu-discuss <qemu-discuss@nongnu.org>
> Subject: Re: how to include out of tree source during the qemu build?
> 
> On Thu, 20 May 2021 at 06:11, <ckim@etri.re.kr> wrote:
> > I’m trying to include a out-of-tree source in a peripheral model and
> want to connect to a .so file during qemu operation.
> >
> > (This .so files was made by my colleague and contains the behaviors of a
> peripheral.
> >
> > I want to place the codes needed to link to this .so file outside the
> source tree as much as possible and use #include or VPATH in Makefile.
> >
> > I’ll use dlopen and dlsym functions to the .so file and use the
> functions there).
> >
> > If I want to add an include path or VPATH, where should I give them
> during the configure/make process and how?
> 
> You're largely on your own here:
>  (1) you're using an old version of QEMU which predates the complete
>      overhaul of the build system
>  (2) you're trying to do something that upstream has very little
>      interest in
> 
> I would probably try to treat this .so file like any other library that
> QEMU might need to use -- have configure find it and set up any
> cflags/ldflags settings necessary to compile and link to it.
> 
> > Also, I started reading
> https://qemu.readthedocs.io/en/latest/devel/build-system.html but this is
> for the latest version.
> >
> > And in this documents, it says it shows how to build qemu under the
> source tree and out of tree.
> >
> > In the out of tree build option header, it says, “VPATH, build artifacts
> outside of QEMU source tree entirely” and I can’t understand why it
> contains the word VPATH.
> 
> The old (pre-meson) build system used GNU Make's VPATH feature
> https://www.gnu.org/software/make/manual/html_node/General-Search.html
> in order to support "run make in a build directory that is not the same as
> the source directory". Under meson we still support that (and indeed we
> now *only* support source-and-build-trees different), but the mechanism
> has changed. The build-system docs should probably not really use the word
> "VPATH" any longer as it's a bit confusing.
> 
> > And this document is for the latest version.(6.x.x) but where can I read
> the equivalent document for version 5.1.0?
> 
> It will be in the source tree for 5.1.0, or it won't exist at all because
> we hadn't documented the build system yet.
> 
> thanks
> -- PMM