Re: ANNOUNCE: pahole v1.24 (Faster BTF encoding, 64-bit BTF enum entries)

[Nathan Chancellor <nathan@kernel.org>]

Hi Arnaldo,

On Mon, Aug 22, 2022 at 08:28:42PM -0300, Arnaldo Carvalho de Melo wrote:
> Hi,
>   
> 	The v1.24 release of pahole and its friends is out, with faster
> BTF generation by parallelizing the encoding part in addition to the
> previoulsy parallelized DWARF loading, support for 64-bit BTF enumeration
> entries, signed BTF encoding of 'char', exclude/select DWARF loading
> based on the language that generated the objects, etc.

<snip>

> - Introduce --lang and --lang_exclude to specify the language the
>   DWARF compile units were originated from to use or filter.

This appears to break building pahole with older versions of libdw (?).
I build container images with older versions of compilers for easy
matrix testing and my gcc-5 and gcc-6 images (based off Ubuntu Xenial
and Debian Stretch respectively) fail to build.

    $ podman run --rm -ti -v $TMP_FOLDER/dwarves-1.24.tar.xz:/tmp/dwarves-1.24.tar.xz:ro docker.io/ubuntu:xenial
    # apt update
    # apt install build-essential cmake libdw-dev libelf-dev xz-utils zlib1g-dev
    # cd $(mktemp -d)
    # tar -xJf /tmp/dwarves-1.24.tar.xz
    # mkdir build
    # cd build
    # cmake -DBUILD_SHARED_LIBS=OFF -D__LIB=lib ../dwarves-1.24
    # make -j$(nproc)
    ...
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c: In function 'lang__str2int':
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2093:3: error: 'DW_LANG_BLISS' undeclared (first use in this function)
      [DW_LANG_BLISS]   = "bliss",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2093:3: note: each undeclared identifier is reported only once for each function it appears in
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2093:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2093:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2100:3: error: 'DW_LANG_C_plus_plus_03' undeclared (first use in this function)
      [DW_LANG_C_plus_plus_03] = "c++03",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2100:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2100:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2105:3: error: 'DW_LANG_Dylan' undeclared (first use in this function)
      [DW_LANG_Dylan]   = "dylan",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2105:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2105:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2114:3: error: 'DW_LANG_Julia' undeclared (first use in this function)
      [DW_LANG_Julia]   = "julia",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2114:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2114:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2116:3: error: 'DW_LANG_Modula3' undeclared (first use in this function)
      [DW_LANG_Modula3]  = "modula3",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2116:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2116:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2119:3: error: 'DW_LANG_OCaml' undeclared (first use in this function)
      [DW_LANG_OCaml]   = "ocaml",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2119:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2119:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2120:3: error: 'DW_LANG_OpenCL' undeclared (first use in this function)
      [DW_LANG_OpenCL]  = "opencl",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2120:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2120:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2122:3: error: 'DW_LANG_PLI' undeclared (first use in this function)
      [DW_LANG_PLI]   = "pli",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2122:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2122:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2124:3: error: 'DW_LANG_RenderScript' undeclared (first use in this function)
      [DW_LANG_RenderScript]  = "renderscript",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2124:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2124:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2125:3: error: 'DW_LANG_Rust' undeclared (first use in this function)
      [DW_LANG_Rust]   = "rust",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2125:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2125:3: note: (near initialization for 'languages')
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2126:3: error: 'DW_LANG_Swift' undeclared (first use in this function)
      [DW_LANG_Swift]   = "swift",
       ^
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2126:3: error: array index in initializer not of integer type
    /tmp/tmp.pQ2GsHbGAx/dwarves-1.24/dwarves.c:2126:3: note: (near initialization for 'languages')
    CMakeFiles/dwarves.dir/build.make:62: recipe for target 'CMakeFiles/dwarves.dir/dwarves.c.o' failed
    ...

If there is any additional information I can provide or patches I can
test, please let me know!

Cheers,
Nathan