Memcached 编译安装

http://ihacklog.com/linux/memcached-compilation.html

Memcached :1.4.5

libevent-1.4.13-stable

Linux ubuntu 3.2.0-23-generic 64位 Server版本

gcc 4.6.3

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wget http://memcached.org/latest tar -xvzf memcached-1.4.5.tar.gz cd memcached-1.4.5 ./configure sudo make

报错：

make all-recursive
make[1]: Entering directory `/usr/local/src/memcached-1.4.5′
Making all in doc
make[2]: Entering directory `/usr/local/src/memcached-1.4.5/doc’
make all-am
make[3]: Entering directory `/usr/local/src/memcached-1.4.5/doc’
make[3]: Nothing to be done for `all-am’.
make[3]: Leaving directory `/usr/local/src/memcached-1.4.5/doc’
make[2]: Leaving directory `/usr/local/src/memcached-1.4.5/doc’
make[2]: Entering directory `/usr/local/src/memcached-1.4.5′
gcc -std=gnu99 -DHAVE_CONFIG_H -I. -DNDEBUG -g -O2 -pthread -Wall -Werror -pedantic -Wmissing-prototypes -Wmissing-declarations -Wredundant-decls -MT memcached-memcached.o -MD -MP -MF .deps/memcached-memcached.Tpo -c -o memcached-memcached.o `test -f ‘memcached.c’ || echo ‘./’`memcached.c
memcached.c: In function ‘complete_incr_bin’:
memcached.c:1023:16: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:1044:13: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:1061:17: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘process_bin_get’:
memcached.c:1193:9: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘process_bin_update’:
memcached.c:1889:5: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:1905:5: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘process_bin_append_prepend’:
memcached.c:1949:5: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘process_bin_delete’:
memcached.c:2014:9: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘do_store_item’:
memcached.c:2127:9: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2127:9: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2144:25: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2145:25: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2158:13: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2160:17: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2160:17: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2202:13: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c:2214:9: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘process_get_command’:
memcached.c:2592:45: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘process_update_command’:
memcached.c:2751:5: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘do_add_delta’:
memcached.c:2870:9: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
memcached.c: In function ‘main’:
memcached.c:4630:13: error: variable ‘udp_port’ set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

make[2]: *** [memcached-memcached.o] Error 1
make[2]: Leaving directory `/usr/local/src/memcached-1.4.5′
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/local/src/memcached-1.4.5′
make: *** [all] Error 2

解决办法，打补丁：

1 2	sudo wget http://johntech-resource.googlecode.com/files/fix-strict-aliasing.patch sudo patch memcached.h fix-strict-aliasing.patch

如果不打补丁的话，这里也有个解决办法：
http://d.hatena.ne.jp/rougeref/comment?date=20100818
即CFLAGS里的-Werror选项去掉（-Werror 将所有警告转换为错误）：

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$ diff configure configure.bak  7917c7917 <   CFLAGS="$CFLAGS -Wall -pedantic -Wmissing-prototypes -Wmissing-declarations -Wredundant-decls" --- >   CFLAGS="$CFLAGS -Wall -Werror -pedantic -Wmissing-prototypes -Wmissing-declarations -Wredundant-decls"

再make ,又报错了：

memcached.c: In function ‘main’:
memcached.c:4630:13: error: variable ‘udp_port’ set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

items.c: In function ‘do_item_stats_sizes’:
items.c:453:21: error: variable ‘klen’ set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

解决办法：

1	sudo vim Makefile

添加 “-Wno-error=unused-but-set-variable” 到 CFLAGS.

1 2	sudo make && sudo make test sudo make install

OK,这下终于通过了。
之所以出这个错误是因为Makefile里面指定了C99的标准。

MORE（以下摘自WWW）：

warning: dereferencing type-punned pointer will break strict-aliasing rules

　　在 gcc 2.x 下编译没有任何 warning 信息的代码换到 gcc 3.x 版本下之后出现了类似的 warning 。原因是 gcc 3 引入了 strict aliasing 架构，当编译时使用了 -fstrict-aliasing 参数（该参数在使用了 -O2 , -O3, -Os 优化参数的情况下默认生效），而源代码中存在一些违反了 strict-aliasing 规则的地方的话，编译器就会对这部分代码提出 warning 。

　　gcc 3 manual 对于 -fstrict-aliasing 参数的说明是：Allows the compiler to assume the strictest aliasing rules applicable to the language being compiled. For C (and C++), this activates optimizations based on the type of expressions. In particular, an object of one type is assumed never to reside at the same address as an object of a different type, unless the types are almost the same. For example, an “unsigned int” can alias an “int”, but not a “void*” or a “double”. A character type may alias any other type.

　　简而言之， 在该参数激活的情况下，编译器希望不同类型的对象不会指向同一个地址。比如像这段代码：

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int retLen; someSetFunc((unsigned long *)&retLen); printf ("ret len = %d\n" ,retLen);

　　由于 someSetFunc 的传入参数类型定义为 unsigned long ，所以需要进行这样的指针类型强制 cast 。但对于 -fstrict-aliasing 优化参数来说，这样的转换是有潜在问题的（但实际上可能并不会造成任何问题）。所以如果现有的源代码存在太多这样的类型强制转换的问题的话，对这些代码进行修改也许会是场噩梦。最简单的方法是使用 -fno-strict-aliasing 参数来关闭 gcc 的优化选项，代价是放弃了 strict-aliasing 编译优化可能带来的可执行代码的性能提升。当然也可以用 -Wno-strict-aliasing 来屏蔽相关的 warning 信息，但无论这些 warning 信息多么的无关紧要，总还是“疑似危险”，所以可能的话最好还是把所有的 warning 都消灭掉。

　　消灭的方法也不算复杂，正如 gcc manual 所示的那样，可以是采用 union 的不同成员变量来完成类型的转换。上面那段代码可以改为：

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union u_retLen { int retLen; unsigned long ptr; }; someSetFunc(&u_retLen.ptr); printf ("ret len = %d\n" ,u_retLen.retLen);

　　虽然会使源代码变得丑陋，但对于大部分已有的源代码来说，这可能是改动最小的方案了。而对于新写的代码来说，如何更好的设计函数的入口参数（比如使用 void*）可能才是需要去思考的问题了。