- check-rpaths的问题
今天在编译varnish的时候，遇到几个问题，其中一个就是出现如下错误：
...
+ /usr/lib/rpm/check-rpaths /usr/lib/rpm/check-buildroot *******************************************************************************
*
* WARNING: 'check-rpaths' detected a broken RPATH and will cause 'rpmbuild'
* to fail. To ignore these errors, you can set the '$QA_RPATHS'
* environment variable which is a bitmask allowing the values
* below. The current value of QA_RPATHS is 0x0000.
*
* 0x0001 ... standard RPATHs (e.g. /usr/lib); such RPATHs are a minor
* issue but are introducing redundant searchpaths without
* providing a benefit. They can also cause errors in multilib
* environments.
* 0x0002 ... invalid RPATHs; these are RPATHs which are neither absolute
* nor relative filenames and can therefore be a SECURITY risk
* 0x0004 ... insecure RPATHs; these are relative RPATHs which are a
* SECURITY risk
* 0x0008 ... the special '$ORIGIN' RPATHs are appearing after other
* RPATHs; this is just a minor issue but usually unwanted
* 0x0010 ... the RPATH is empty; there is no reason for such RPATHs
* and they cause unneeded work while loading libraries
* 0x0020 ... an RPATH references '..' of an absolute path; this will break
* the functionality when the path before '..' is a symlink
*
*
* Examples:
* - to ignore standard and empty RPATHs, execute 'rpmbuild' like
* $ QA_RPATHS=$[ 0x0001|0x0010 ] rpmbuild my-package.src.rpm
* - to check existing files, set $RPM_BUILD_ROOT and execute check-rpaths like
* $ RPM_BUILD_ROOT=<top-dir> /usr/lib/rpm/check-rpaths
*
******************************************************************************* ERROR : file 'xxx.so' contains an invalid rpath 'xxx' in [xxx]
...
参考 https://fedoraproject.org/wiki/Packaging:Guidelines， 其中说道：
Sometimes, code will hardcode specific library paths when linking binaries (using the -rpath or -R flag). This is commonly referred to as an rpath. Normally, the dynamic linker and loader (ld.so) resolve the executable's dependencies on shared libraries and load what is required. However, when -rpath or -R is used, the location information is then hardcoded into the binary and is examined by ld.so in the beginning of the execution. Since the Linux dynamic linker is usually smarter than a hardcoded path, we usually do not permit the use of rpath in Fedora.
There is a tool called check-rpaths which is included in the rpmdevtools package. It is a good idea to add it to the %__arch_install_post macro in your ~/.rpmmacros config file:
由此可知，这一步只是一种检测是不是代码中使用了rpath，那我们可以简单的注释掉rpath检测就可以了，具体做法就是：
vi ~/.rpmmacros
%_topdir %(echo $HOME)/rpmbuild
%_smp_mflags -j3
#%__arch_install_post /usr/lib/rpm/check-rpaths /usr/lib/rpm/check-buildroot
后面就能顺利编译了
- pkgconfig跟ldconfig， ldd的问题
先看下面的说明：
1. The pkgconfig package contains tools for passing the include path and/or library paths to build tools during the make file execution.
pkg-config is a function that returns meta information for the specified library.
The default setting for PKG_CONFIG_PATH is /usr/lib/pkgconfig because of the prefix we use to install pkgconfig. You may add to PKG_CONFIG_PATH by exporting additional paths on your system where pkgconfig files are installed. Note that PKG_CONFIG_PATH is only needed when compiling packages, not during run-time.
上面的解释够清楚了，pkg-config是用来在执行makefile时指定头文件和库文件的路径。它到由环境变量PKG_CONFIG_PATH指定的路径下(默认为/usr/lib/config)去找对应库的*.pc文件，*.pc文件记录了包之间的倚赖关系、头文件和库文件包含路径、版本等信息。
2. /etc/ld.so.conf.d/* 或/etc/ld.so.conf和ldconfig.
/etc/ld.so.conf.d/*目录下的文件和/etc/ld.so.conf记录了动态链接库的路径，系统默认搜索/lib和 /usr/lib，在其他路径下的库文件就需在这些文件中指定。或者，还有个方法，就是设置LD_LIBRARY_PATH环境变量，添加其他路径，多个 中间用：分隔开。
ldconfig是一个用来将/etc/ld.so.conf.d/*h 和/etc/ld.so.conf中列出的库缓存到/etc/ld.so.cache文件中以供使用，因此在装完一些库或更新/etc/ld.so.conf文件时，需运行/sbin/ldconfig命令一下。
当运行 ./configure 产生Makefile的过程中出现, pkg-config有问题，或是不能找到对应的lib文件的时候。
不妨重新设置下pkgconfig的两个变量：
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:/usr/share/pkgconfig:$PKG_CONFIG_PATH
export PKG_CONFIG=/usr/bin/pkg-config
并且重新加载下动态链接库
ldconfig
另外一个非常实用的调试脚本就是ldd:
[root@xx pcre-8.34]# ldd /bin/ls
linux-vdso.so. => (0x00007fff2a5ff000)
libselinux.so. => /lib64/libselinux.so. (0x00007fec45edf000)
librt.so. => /lib64/librt.so. (0x00007fec45cd7000)
libcap.so. => /lib64/libcap.so. (0x00007fec45ad2000)
libacl.so. => /lib64/libacl.so. (0x00007fec458ca000)
libc.so. => /lib64/libc.so. (0x00007fec45536000)
libdl.so. => /lib64/libdl.so. (0x00007fec45331000)
/lib64/ld-linux-x86-.so. (0x00007fec46105000)
libpthread.so. => /lib64/libpthread.so. (0x00007fec45114000)
libattr.so. => /lib64/libattr.so. (0x00007fec44f0f000)
[root@xx pcre-8.34]#
其本质也就是设置诸如LD_DEBUG等环境变量，在程序运行时，打印出调用的动态链接库。