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

[Yang Jihong <yangjihong@bytedance.com>]

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@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?
Yes, have tested it in my environment and it works for me.
OK, will change in next version.

Thanks,
Yang