Re: [PATCH v2 1/3] perf: build: Fix static compilation error when libdw is not installed

[Leo Yan <leo.yan@arm.com>]

On 8/6/2024 12:47 PM, Yang Jihong wrote:
> If libdw is not installed in build environment, the output of
> 'pkg-config --modversion libdw' is empty, causing LIBDW_VERSION_2
> to be empty and the shell test will have the following error:
> 
>   /bin/sh: 1: test: -lt: unexpected operator
> 
> Before:
> 
>   $ pkg-config --modversion libdw
>   Package libdw was not found in the pkg-config search path.
>   Perhaps you should add the directory containing `libdw.pc'
>   to the PKG_CONFIG_PATH environment variable
>   No package 'libdw' found
>   $ make LDFLAGS=-static -j16
>     BUILD:   Doing 'make -j20' parallel build
>   <SNIP>
>   Package libdw was not found in the pkg-config search path.
>   Perhaps you should add the directory containing `libdw.pc'
>   to the PKG_CONFIG_PATH environment variable
>   No package 'libdw' found
>   /bin/sh: 1: test: -lt: unexpected operator
> 
> After:
> 
>   1. libdw is not installed:
> 
>   $ pkg-config --modversion libdw
>   Package libdw was not found in the pkg-config search path.
>   Perhaps you should add the directory containing `libdw.pc'
>   to the PKG_CONFIG_PATH environment variable
>   No package 'libdw' found
>   $ make LDFLAGS=-static -j16
>     BUILD:   Doing 'make -j20' parallel build
>   <SNIP>
>   Package libdw was not found in the pkg-config search path.
>   Perhaps you should add the directory containing `libdw.pc'
>   to the PKG_CONFIG_PATH environment variable
>   No package 'libdw' found
>   Makefile.config:473: No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR
> 
>   2. libdw version is lower than 0.177
> 
>   $ pkg-config --modversion libdw
>   0.176
>   $ make LDFLAGS=-static -j16
>     BUILD:   Doing 'make -j20' parallel build
>   <SNIP>
> 
>   Auto-detecting system features:
>   ...                                   dwarf: [ on  ]
>   <SNIP>
>     INSTALL libsubcmd_headers
>     INSTALL libapi_headers
>     INSTALL libperf_headers
>     INSTALL libsymbol_headers
>     INSTALL libbpf_headers
>     LINK    perf
> 
>   3. libdw version is higher than 0.177
> 
>   $ pkg-config --modversion libdw
>   0.186
>   $ make LDFLAGS=-static -j16
>     BUILD:   Doing 'make -j20' parallel build
>   <SNIP>
> 
>   Auto-detecting system features:
>   ...                                   dwarf: [ on  ]
>   <SNIP>
>     CC      util/bpf-utils.o
>     CC      util/pfm.o
>     LD      util/perf-util-in.o
>     LD      perf-util-in.o
>     AR      libperf-util.a
>     LINK    perf
> 
> Fixes: 536661da6ea1 ("perf: build: Only link libebl.a for old libdw")
> Signed-off-by: Yang Jihong <yangjihong@bytedance.com>
> ---
>  tools/build/feature/Makefile | 2 +-
>  tools/perf/Makefile.config   | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> index 12796808f07a..b18513ec4da6 100644
> --- a/tools/build/feature/Makefile
> +++ b/tools/build/feature/Makefile
> @@ -178,7 +178,7 @@ ifeq ($(findstring -static,${LDFLAGS}),-static)
> 
>    # Elfutils merged libebl.a into libdw.a starting from version 0.177,
>    # Link libebl.a only if libdw is older than this version.
> -  ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
> +  ifeq ($(shell test $(LIBDW_VERSION_2)0 -lt 1770; echo $$?),0)

I would like to follow up the style of LIBTRACEEVENT_VERSION and
LIBTRACEFS_VERSION, so change LIBDW_VERSION as below:

  LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw).0.0

Does this work for you?

Thanks,
Leo