[PATCH RESEND v3 1/3] perf: build: Fix static compilation error when libdw is not installed

Yang Jihong
2024-09-19T01:35:41Z

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")
Reviewed-by: Leo Yan <leo.yan@arm.com>
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 5938cf799dc6..6f1c961f0ede 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -172,7 +172,7 @@ DWARFLIBS := -ldw
ifeq ($(findstring -static,${LDFLAGS}),-static)
DWARFLIBS += -lelf -lz -llzma -lbz2 -lzstd

- LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw)
+ LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw).0.0
LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
LIBDW_VERSION_2 := $(word 2, $(subst ., ,$(LIBDW_VERSION)))

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 4dcf7a0fd235..0049fd41cf57 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -149,7 +149,7 @@ DWARFLIBS := -ldw
ifeq ($(findstring -static,${LDFLAGS}),-static)
DWARFLIBS += -lelf -ldl -lz -llzma -lbz2 -lzstd

- LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw)
+ LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw).0.0
LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
LIBDW_VERSION_2 := $(word 2, $(subst ., ,$(LIBDW_VERSION)))

--
2.25.1