Re: Linker failures trying to build static qemu-user binary

[John Paul Adrian Glaubitz]

Hi!

On Thu, 2023-02-09 at 14:14 +0000, Peter Maydell wrote:
> The "Using getpwuid in statically linked applications" etc warnings
> are expected, so we can ignore those; this is the key error:

OK.

> > /usr/bin/ld: /usr/lib/x86_64-linux-gnu/libdw.a(debuginfod-client.o): in 
> > function `__libdwfl_debuginfod_init':
> > (.text.startup+0x17): undefined reference to `dlopen'
> > /usr/bin/ld: (.text.startup+0x32): undefined reference to `dlsym'
> > /usr/bin/ld: (.text.startup+0x4b): undefined reference to `dlsym'
> > /usr/bin/ld: (.text.startup+0x64): undefined reference to `dlsym'
> > /usr/bin/ld: (.text.startup+0x7d): undefined reference to `dlsym'
> > /usr/bin/ld: (.text.startup+0xdc): undefined reference to `dlclose'
> > collect2: error: ld returned 1 exit status
> 
> We use pkg-config to find out what the libdw library needs on
> the compiler/linker command line to link successfully, so
> maybe your distro's pkg-config info isn't right. What does
> "pkg-config --static --libs libdw" say ?

glaubitz@nofan:~> pkg-config --static --libs libdw
-ldw -lbz2 -llzma -pthread -lpthread -lelf -lz
glaubitz@nofan:~>

I'm building on Debian stable (Bullseye).

> If libdw needs libdl
> then it ought to list it in that output, I think. IME pkg-config
> information is often incorrect for static linking, though.
> I guess this one happened to work previously because glibc didn't
> actually mandate linking with '-ldl', and now on your system it
> apparently does. On my system pkg-config says
> -ldw -lbz2 -llzma -pthread -lpthread -lelf -lz
> which looks like it's missing -ldl, but the link succeeds anyway,
> presumably because the symbols are provided by the main glibc .a.
> 
> On the other hand, if libdw wants to use dlopen/dlsym then
> I wonder if we should just suppress it for static linking:
> on my (Ubuntu 22.04) ld warns:
> /usr/bin/ld: /usr/lib/x86_64-linux-gnu/libdw.a(debuginfod-client.o):
> in function `__libdwfl_debuginfod_init':
> (.text.startup+0x1b): warning: Using 'dlopen' in statically linked
> applications requires at runtime the shared libraries from the glibc
> version used for linking
> 
> so whatever libdw is trying to do will likely not work in most
> statically-linked situations anyway.

So, just include "-ldl" in LD_FLAGS?

> I've cc'd the author of the commit that added the libdw
> dependency.

Thank you!

Adrian

-- 
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