Alpine静态编译PHP 8.1.7添加--with-readline时报readline库未找到错误

问题场景 #

在最新版Alpine Linux环境中静态编译PHP 8.1.7，无readline支持时使用以下命令可顺利完成编译：

./configure LDFLAGS=-static --disable-all --enable-cli --enable-mbstring --enable-static=yes
sed -ie 's/-export-dynamic//g' "Makefile" && \
    sed -ie 's/-o $(SAPI_CLI_PATH)/-all-static -o $(SAPI_CLI_PATH)/g' "Makefile"
make LDFLAGS="-ldl" -j12
make install

后续需要添加readline支持，先安装readline、ncurses相关的运行时、开发包及静态库，再重新执行configure命令添加--with-readline参数：

apk add readline readline-dev readline-static ncurses-static ncurses-dev
./configure LDFLAGS=-static --disable-all --enable-cli --enable-mbstring --enable-static=yes --with-readline

执行configure配置阶段直接报错中断：

checking for libedit readline replacement... no
checking for readline support... yes
checking for tgetent in -lncurses... no
checking for tgetent in -ltermcap... no
checking for readline in -lreadline... no
configure: error: readline library not found

查看config.log对应报错片段，核心错误有两个：

1. 链接阶段提示cannot find -lncurses、cannot find -ltermcap
2. 尝试链接libreadline.a时出现大量tputs符号未定义错误

configure:84994: checking for tgetent in -lncurses
configure:85017: cc -o conftest -g -O2 -fvisibility=hidden  -static conftest.c -lncurses  -lrt -lm  >&5
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lncurses
collect2: error: ld returned 1 exit status
configure:85027: result: no
configure:85059: checking for tgetent in -ltermcap
configure:85082: cc -o conftest -g -O2 -fvisibility=hidden  -static conftest.c -ltermcap  -lrt -lm  >&5
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -ltermcap
collect2: error: ld returned 1 exit status
configure:85092: result: no
configure:85235: checking for readline in -lreadline
configure:85258: cc -o conftest -g -O2 -fvisibility=hidden  -Wl,-rpath,/usr/local/lib -L/usr/local/lib -static conftest.c -lreadline  -lrt -lm  >&5
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld: /usr/local/lib/libreadline.a(display.o): in function `_rl_move_cursor_relative':
/root/static-php-cli/docker/source/readline-8.1/display.c:2805: undefined reference to `tputs'
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld: /usr/local/lib/libreadline.a(display.o): in function `_rl_move_vert':
/root/static-php-cli/docker/source/readline-8.1/display.c:2857: undefined reference to `tputs'
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld: /usr/local/lib/libreadline.a(terminal.o):/root/static-php-cli/docker/source/readline-8.1/terminal.c:764: more undefined references to `tputs' follow
collect2: error: ld returned 1 exit status
configure:85268: result: no
configure:85381: error: readline library not found

故障根因 #

• Alpine官方源的ncurses静态包默认只提供宽字符版本的静态库libncursesw.a，没有生成libncurses.a、libtermcap.a的兼容软链，导致configure默认查找规则匹配不到库文件
• 静态链接对库的顺序有严格要求，被依赖的库必须放在依赖它的库后面，PHP的configure脚本检测readline时默认不会主动追加ncurses链接参数，导致readline依赖的终端控制符号找不到

解决步骤 #

• 创建ncurses库兼容软链，匹配configure的默认查找规则

ln -sf /usr/lib/libncursesw.a /usr/lib/libncurses.a
ln -sf /usr/lib/libncursesw.a /usr/lib/libtermcap.a

• 清空之前编译生成的缓存文件，重新执行configure，显式追加ncurses链接参数

make clean
rm -f config.cache
./configure LDFLAGS="-static -L/usr/local/lib -L/usr/lib" \
  --disable-all --enable-cli --enable-mbstring --enable-static=yes \
  --with-readline LIBS="-lncurses"

• configure执行通过后，修改Makefile移除动态链接参数，同时修正静态链接的库顺序

sed -ie 's/-export-dynamic//g' "Makefile" && \
  sed -ie 's/-o $(SAPI_CLI_PATH)/-all-static -o $(SAPI_CLI_PATH)/g' "Makefile" && \
  sed -ie 's/-lreadline/-lreadline -lncurses/g' "Makefile"

• 执行编译安装

make LDFLAGS="-ldl -lncurses" -j$(nproc)
make install

结果验证 #

• 执行php -m | grep readline，输出readline即模块加载正常
• 执行ldd $(which php)，输出not a dynamic executable即确认为静态编译版本

内容的提问来源于stack exchange，提问作者Jerry