Re: [PATCH v2 1/2] CMakeLists.txt: enable SHARED and STATIC lib creation

[Luca Boccassi <bluca@debian.org>]

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On Sat, 2021-06-12 at 07:53 +0900, Dominique Martinet wrote:
> Luca Boccassi wrote on Fri, Jun 11, 2021 at 11:45:25PM +0100:
> > Actually that was my mistake, used the wrong build tree (sorry,
> > it's
> > late!). I can however reproduce the issue in a chroot running the
> > libbpf CI script. Still looking.
> 
> with the ci script I get
> 
> $ /usr/lib64/ccache/cc -DDWARVES_MAJOR_VERSION=1 -
> DDWARVES_MINOR_VERSION=21 -D_GNU_SOURCE -Ddwarves_EXPORTS -
> I/path/to/pahole/build -I/path/to/pahole -
> I/path/to/pahole/lib/include -I/path/to/pahole/lib/bpf/include/uapi -
> D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g -DNDEBUG -fPIC -MD
> -MT CMakeFiles/dwarves.dir/btf_encoder.c.o -MF
> CMakeFiles/dwarves.dir/btf_encoder.c.o.d -o
> CMakeFiles/dwarves.dir/btf_encoder.c.o -c
> /path/to/pahole/btf_encoder.c
> /path/to/pahole/btf_encoder.c: In function ‘btf_encoder__add_float’:
> /path/to/pahole/btf_encoder.c:224:22: warning: implicit declaration
> of function ‘btf__add_float’; did you mean ‘btf__add_var’? [-
> Wimplicit-function-declaration]
>   224 |         int32_t id = btf__add_float(encoder->btf, name,
> BITS_ROUNDUP_BYTES(bt->bit_size));
>       |                      ^~~~~~~~~~~~~~
>       |                      btf__add_var
> 
> 
> 
> with btf__add_float defined in .../pahole/lib/bpf/src/btf.h
> and btf_encoder.c including linux/btf.h
> 
> 
> changing btf_loader.c to include bpf/btf.h instead fixes the issue
> for me:
> 
> diff --git a/btf_loader.c b/btf_loader.c
> index 75ec674b3b3e..272c73bca7fe 100644
> --- a/btf_loader.c
> +++ b/btf_loader.c
> @@ -20,7 +20,7 @@
>  #include <string.h>
>  #include <limits.h>
>  #include <libgen.h>
> -#include <linux/btf.h>
> +#include <bpf/btf.h>
>  #include <bpf/libbpf.h>
>  #include <zlib.h>

I've just sent a patch - the issue is that the original commit included
a symlink lib/include/bpf -> ../bpf/src as suggested by Andrii here:

https://www.spinics.net/lists/dwarves/msg00738.html

git show 82749180b23d3c9c060108bc290ae26507fc324e -- lib/include
    commit 82749180b23d3c9c060108bc290ae26507fc324e
    Author: Luca Boccassi <bluca@debian.org>
    Date:   Mon Jan 4 22:16:22 2021 +0000
    
        libbpf: allow to use packaged version
    
        Add a new CMake option, LIBBPF_EMBEDDED, to switch between the
        embedded version and the system version (searched via pkg-config)
        of libbpf. Set the embedded version as the default.
    
        Signed-off-by: Luca Boccassi <bluca@debian.org>
        Cc: dwarves@vger.kernel.org
        Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    
    diff --git a/lib/include/bpf b/lib/include/bpf
    new file mode 120000
    index 0000000..4c41b71
    --- /dev/null
    +++ b/lib/include/bpf
    @@ -0,0 +1 @@
    +../bpf/src
    \ No newline at end of file

When the patch was reverted and re-added, the symlink was dropped.

It stayed in my local tree, and I completely missed it - that's why the
build was working fine for me! D'oh!
Adding the symlink back fixes the build with the libbpf CI script. I
would be grateful if folks who are seeing the issue could apply the
patch (or create the symlink) and confirm whether it fixes the problem
or not. Thanks!

-- 
Kind regards,
Luca Boccassi

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