configure配置
nginx的编译过程，第一步是configure。我们使用 --help可以看到configure的很多配置。
configure的过程做的事情其实就是检测环境，然后根据环境生成Makefile，包含各种参数的c头文件等（ngx_auto_config.h/ ngx_auto_headers.h）。这个c头文件包含了所有根据当前环境配置的参数。
configure命令 之后多了些什么？
多了一个Makefile文件
这里的Makefile文件指的是根目录下的Makefile, 这个是后面make命令的入口
多了一个objs文件夹
objs文件夹里面有这几个文件：
autoconf.err
configure过程中不仅仅是使用简单的shell命令来检测环境，还会生成一些简单的c程序，并且用编译器编译执行，获取输出来获取环境参数。只是这些c程序和编译后的文件在获取参数完成之后会删除，所以我们实际看不到这个文件的存在。
这些shell命令，c程序的一些输出和错误信息都记录在这个autoconf.err中了，实际上这个文件没有什么用。
Makefile
这个obj/Makefile才是本质的构建程序和模块的过程。所有需要加载的模块和一些设置都在这边了。
我们可以看一下，它使用的编译器是cc， cc编译器在linux上就是gcc。 gcc是一个各种不同语言的编译器。gcc代表 the GNU Compiler Collection。 比如你的代码后缀是.c， 它会调用c的编译器还有linker去链接c的库。
nginx_auto_config.h
这个就是configure出来的一个重要成果，本机环境的一些配置，比如int多少位之类的。
nginx_auto_headers.h
这个是configure出来的，判断一些header是否存在。
nginx_modules.c
这个文件就告诉我们了我们这次编译nginx到底有多少个模块。
其中的一些模块是很重要的，但是我们也可以自主选择。
configure的语法
have + auto/define 语法
have=NGX_SBIN_PATH value=""$NGX_SBIN_PATH"" . auto/define
auto/define的定义：
# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.
cat << END >> $NGX_AUTO_CONFIG_H
#ifndef $have
#define $have $value
#endif
END
结合起来的意思就是，如果我在参数里面设置了NGX_SBIN_PATH（有参数可以设置），那么我就在ngx_auto_config.h中增加这个宏定义：
#ifndef NGX_SBIN_PATH
#define NGX_SBIN_PATH "sbin/nginx"
#endif
have + auto/have 语法
cat << END >> $NGX_AUTO_CONFIG_H
#ifndef $have
#define $have 1
#endif
END
意思其实就是auto/define的翻版，只是如果这里的value是1
比如
have=NGX_HAVE_EPOLL . auto/have
等同
#ifndef NGX_HAVE_EPOLL
#define NGX_HAVE_EPOLL 1
#endif
auto/feature
ngx_feature="GeoIP IPv6 support"
ngx_feature_name="NGX_HAVE_GEOIP_V6"
ngx_feature_run=no
ngx_feature_incs="#include <stdio.h>
#include <GeoIP.h>"
#ngx_feature_path=
#ngx_feature_libs=
ngx_feature_test="printf("%d", GEOIP_CITY_EDITION_REV0_V6);"
. auto/feature
上面这个是个feature的模版，它的目的是为了检查当前的环境是否包含这个feature, 比如上面的例子就是判断这个机器环境是否支持GEO IPV6。
还可以看看下面这个例子：
ngx_feature="GeoIP library in /opt/local/"
ngx_feature_path="/opt/local/include"
if [ $NGX_RPATH = YES ]; then
ngx_feature_libs="-R/opt/local/lib -L/opt/local/lib -lGeoIP"
else
ngx_feature_libs="-L/opt/local/lib -lGeoIP"
fi
. auto/feature
feature的代码就不贴出来了, 具体做了下面几个事情：
- 控制台先输出checking for
- 在auto_config.err中输出checking for
- 检查变量$ngx_feature_name是否有设置
- 如果设置了ngx_feature_path，就设置ngx_feature_inc_path
- 根据$ngx_feature_test生成测试c文件
- 编译生成的测试c文件
- 执行测试c文件并捕获输出到auto_config.err
- 如果设置了ngx_feature_run, 就把输出设置为对应的$ngx_feature_name的值
- 没有找到的情况，在auto_config.err中体现，并且在控制台显示 not found
- 删除测试c文件及编译出来的东西
auto/include
ngx_include="inttypes.h"; . auto/include
生成一个简单的c文件：
cat << END > $NGX_AUTOTEST.c
$NGX_INCLUDE_SYS_PARAM_H
#include <$ngx_include>
int main(void) {
return 0;
}
END
判断检测环境是否有这个头文件。
auto/module
ngx_module_type=HTTP
if :; then
ngx_module_name="ngx_http_module
ngx_http_core_module
ngx_http_log_module
ngx_http_upstream_module"
ngx_module_incs="src/http src/http/modules"
ngx_module_deps="src/http/ngx_http.h
src/http/ngx_http_request.h
src/http/ngx_http_config.h
src/http/ngx_http_core_module.h
src/http/ngx_http_cache.h
src/http/ngx_http_variables.h
src/http/ngx_http_script.h
src/http/ngx_http_upstream.h
src/http/ngx_http_upstream_round_robin.h"
ngx_module_srcs="src/http/ngx_http.c
src/http/ngx_http_core_module.c
src/http/ngx_http_special_response.c
src/http/ngx_http_request.c
src/http/ngx_http_parse.c
src/http/modules/ngx_http_log_module.c
src/http/ngx_http_request_body.c
src/http/ngx_http_variables.c
src/http/ngx_http_script.c
src/http/ngx_http_upstream.c
src/http/ngx_http_upstream_round_robin.c"
ngx_module_libs=
ngx_module_link=YES
. auto/module
这个auto/module会对每一个模块设置一些模块需要的变量，比如模块的源码地址，模块依赖的lib库等。
控制台输出：
checking for OS
+ Linux 3.10.0-514.16.1.el7.x86_64 x86_64
checking for C compiler ... found
+ using GNU C compiler
+ gcc version: 4.4.7 20120313 (Red Hat 4.4.7-18) (GCC)
checking for gcc -pipe switch ... found
checking for -Wl,-E switch ... found
checking for gcc builtin atomic operations ... found
checking for C99 variadic macros ... found
checking for gcc variadic macros ... found
checking for gcc builtin 64 bit byteswap ... found
checking for unistd.h ... found
checking for inttypes.h ... found
checking for limits.h ... found
checking for sys/filio.h ... not found
checking for sys/param.h ... found
checking for sys/mount.h ... found
checking for sys/statvfs.h ... found
checking for crypt.h ... found
checking for Linux specific features
checking for epoll ... found
checking for EPOLLRDHUP ... found
checking for EPOLLEXCLUSIVE ... not found
checking for O_PATH ... not found
checking for sendfile() ... found
checking for sendfile64() ... found
checking for sys/prctl.h ... found
checking for prctl(PR_SET_DUMPABLE) ... found
checking for prctl(PR_SET_KEEPCAPS) ... found
checking for capabilities ... found
checking for crypt_r() ... found
checking for sys/vfs.h ... found
checking for nobody group ... found
checking for poll() ... found
checking for /dev/poll ... not found
checking for kqueue ... not found
checking for crypt() ... not found
checking for crypt() in libcrypt ... found
checking for F_READAHEAD ... not found
checking for posix_fadvise() ... found
checking for O_DIRECT ... found
checking for F_NOCACHE ... not found
checking for directio() ... not found
checking for statfs() ... found
checking for statvfs() ... found
checking for dlopen() ... not found
checking for dlopen() in libdl ... found
checking for sched_yield() ... found
checking for sched_setaffinity() ... found
checking for SO_SETFIB ... not found
checking for SO_REUSEPORT ... found
checking for SO_ACCEPTFILTER ... not found
checking for SO_BINDANY ... not found
checking for IP_TRANSPARENT ... found
checking for IP_BINDANY ... not found
checking for IP_BIND_ADDRESS_NO_PORT ... not found
checking for IP_RECVDSTADDR ... not found
checking for IP_SENDSRCADDR ... not found
checking for IP_PKTINFO ... found
checking for IPV6_RECVPKTINFO ... found
checking for TCP_DEFER_ACCEPT ... found
checking for TCP_KEEPIDLE ... found
checking for TCP_FASTOPEN ... not found
checking for TCP_INFO ... found
checking for accept4() ... found
checking for eventfd() ... found
checking for int size ... 4 bytes
checking for long size ... 8 bytes
checking for long long size ... 8 bytes
checking for void * size ... 8 bytes
checking for uint32_t ... found
checking for uint64_t ... found
checking for sig_atomic_t ... found
checking for sig_atomic_t size ... 4 bytes
checking for socklen_t ... found
checking for in_addr_t ... found
checking for in_port_t ... found
checking for rlim_t ... found
checking for uintptr_t ... uintptr_t found
checking for system byte ordering ... little endian
checking for size_t size ... 8 bytes
checking for off_t size ... 8 bytes
checking for time_t size ... 8 bytes
checking for AF_INET6 ... found
checking for setproctitle() ... not found
checking for pread() ... found
checking for pwrite() ... found
checking for pwritev() ... found
checking for sys_nerr ... found
checking for localtime_r() ... found
checking for clock_gettime(CLOCK_MONOTONIC) ... not found
checking for clock_gettime(CLOCK_MONOTONIC) in librt ... found
checking for posix_memalign() ... found
checking for memalign() ... found
checking for mmap(MAP_ANON|MAP_SHARED) ... found
checking for mmap("/dev/zero", MAP_SHARED) ... found
checking for System V shared memory ... found
checking for POSIX semaphores ... not found
checking for POSIX semaphores in libpthread ... found
checking for struct msghdr.msg_control ... found
checking for ioctl(FIONBIO) ... found
checking for struct tm.tm_gmtoff ... found
checking for struct dirent.d_namlen ... not found
checking for struct dirent.d_type ... found
checking for sysconf(_SC_NPROCESSORS_ONLN) ... found
checking for sysconf(_SC_LEVEL1_DCACHE_LINESIZE) ... found
checking for openat(), fstatat() ... found
checking for getaddrinfo() ... found
checking for zlib library ... found
creating objs/Makefile
Configuration summary
+ PCRE library is not used
+ OpenSSL library is not used
+ using system zlib library
nginx path prefix: "/usr/local/nginx"
nginx binary file: "/usr/local/nginx/sbin/nginx"
nginx modules path: "/usr/local/nginx/modules"
nginx configuration prefix: "/usr/local/nginx/conf"
nginx configuration file: "/usr/local/nginx/conf/nginx.conf"
nginx pid file: "/usr/local/nginx/logs/nginx.pid"
nginx error log file: "/usr/local/nginx/logs/error.log"
nginx http access log file: "/usr/local/nginx/logs/access.log"
nginx http client request body temporary files: "client_body_temp"
nginx http proxy temporary files: "proxy_temp"
nginx http fastcgi temporary files: "fastcgi_temp"
nginx http uwsgi temporary files: "uwsgi_temp"
nginx http scgi temporary files: "scgi_temp
我们其实可以对着 xmind 的流程和 configure 这个程序来看就很清晰了
https://github.com/its-tech/nginx-1.14.0-research/blob/master/configure
再加上前面几个configure语法就能看懂了。