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

[Yang Jihong]

Hello,

On 8/7/24 05:00, Leo Yan wrote:
> 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@xxxxxxxxxxxxx>
> > ---
> >   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?
Yes, have tested it in my environment and it works for me.
OK, will change in next version.

Thanks,
Yang