Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933367AbcLIFSr (ORCPT ); Fri, 9 Dec 2016 00:18:47 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:62084 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932502AbcLIFSp (ORCPT ); Fri, 9 Dec 2016 00:18:45 -0500 Subject: Re: [PATCHv3 perf/core 5/7] samples/bpf: Switch over to libbpf To: Joe Stringer , References: <20161209024620.31660-1-joe@ovn.org> <20161209024620.31660-6-joe@ovn.org> CC: , , , From: "Wangnan (F)" Message-ID: <77ff1746-6271-0eac-a921-bb852c14a602@huawei.com> Date: Fri, 9 Dec 2016 13:18:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.111.194.139] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1534 Lines: 47 On 2016/12/9 13:04, Wangnan (F) wrote: > > > On 2016/12/9 10:46, Joe Stringer wrote: > > [SNIP] > >> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile >> index 62d89d50fcbd..616bd55f3be8 100644 >> --- a/tools/lib/bpf/Makefile >> +++ b/tools/lib/bpf/Makefile >> @@ -149,6 +149,8 @@ CMD_TARGETS = $(LIB_FILE) >> TARGETS = $(CMD_TARGETS) >> +libbpf: all >> + > > Why we need this? I tested this patch without it and it seems to work, > and > this line causes an extra error: > $ pwd > /home/wn/kernel/tools/lib/bpf > $ make libbpf > ... > gcc -g -Wall -DHAVE_LIBELF_MMAP_SUPPORT -DHAVE_ELF_GETPHDRNUM_SUPPORT > -Wbad-function-cast -Wdeclaration-after-statement -Wformat-security > -Wformat-y2k -Winit-self -Wmissing-declarations -Wmissing-prototypes > -Wnested-externs -Wno-system-headers -Wold-style-definition -Wpacked > -Wredundant-decls -Wshadow -Wstrict-aliasing=3 -Wstrict-prototypes > -Wswitch-default -Wswitch-enum -Wundef -Wwrite-strings -Wformat > -Werror -Wall -fPIC -I. -I/home/wn/kernel-hydrogen/tools/include > -I/home/wn/kernel-hydrogen/tools/arch/x86/include/uapi > -I/home/wn/kernel-hydrogen/tools/include/uapi libbpf.c all -o libbpf > gcc: error: all: No such file or directory > make: *** [libbpf] Error 1 > > Thank you. It is not 'caused' by your patch. 'make libbpf' fails without your change because it tries to build an executable from libbpf.c, but main() is missing. I think libbpf should never be used as a make target. Your new dependency looks strange. Thank you.