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

From: Leo Yan
Date: Tue Aug 06 2024 - 17:01:06 EST


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?

Thanks,
Leo