前言
Apache 2.4 以后的版本不再自带 APR 库（Apache Portable Runtime，Apache 可移植运行库），所以在安装 Apache 之前需要手动下载安装 APR 库。
完整的 APR 实际上包含了三个依赖包：apr、apr-util 以及 apr-iconv。
正文
在官网http://apr.apache.org/下载了 apr-util 包，解压后执行 make 编译时，报错如下：
[root@mingc apr-util-1.6.0]# make
make[1]: Entering directory `/usr/local/src/apr-util-1.6.0'
/bin/sh /usr/local/apr/build-1/libtool --silent --mode=compile gcc -g -O2 -pthread -DHAVE_CONFIG_H -DLINUX -D_REENTRANT -D_GNU_SOURCE -I/usr/local/src/apr-util-1.6.0/include -I/usr/local/src/apr-util-1.6.0/include/private -I/usr/local/apr/include/apr-1 -o xml/apr_xml.lo -c xml/apr_xml.c && touch xml/apr_xml.lo
xml/apr_xml.c:35:19: error: expat.h: No such file or directory
xml/apr_xml.c:66: error: expected specifier-qualifier-list before ‘XML_Parser’
xml/apr_xml.c: In function ‘cleanup_parser’:
xml/apr_xml.c:364: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:365: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c: At top level:
xml/apr_xml.c:384: error: expected ‘;’, ‘,’ or ‘)’ before ‘*’ token
xml/apr_xml.c: In function ‘apr_xml_parser_create’:
xml/apr_xml.c:401: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:402: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:410: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:411: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:412: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:424: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:424: error: ‘default_handler’ undeclared (first use in this function)
xml/apr_xml.c:424: error: (Each undeclared identifier is reported only once
xml/apr_xml.c:424: error: for each function it appears in.)
xml/apr_xml.c: In function ‘do_parse’:
xml/apr_xml.c:434: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:438: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c:442: error: ‘apr_xml_parser’ has no member named ‘xp_err’
xml/apr_xml.c:442: error: ‘apr_xml_parser’ has no member named ‘xp’
xml/apr_xml.c: In function ‘apr_xml_parser_geterror’:
xml/apr_xml.c:500: error: ‘apr_xml_parser’ has no member named ‘xp_err’
xml/apr_xml.c:500: error: ‘apr_xml_parser’ has no member named ‘xp_err’
make[1]: *** [xml/apr_xml.lo] Error 1
make[1]: Leaving directory `/usr/local/src/apr-util-1.6.0'
make: *** [all-recursive] Error 1
大致是说缺少了 xml 的解析器。查阅网络资料后找到了解决方案，yum 安装一个 expat-devel 包即可：
[root@mingc apr-util-1.6.0]# yum -y install expat-devel