Mac OS下搭建OpenWrt编译环境记录

Mac OS下搭建OpenWrt编译环境记录（针对官方2015.01.20 r44068 trunk）。

前言

之前已经在MacOS下搭建好了OpenWrt的编译环境，没想到更新到最新的官方Trunk之后，噩梦就此开始。现将思考过程以及应对方法做个记录。

背景知识

OpenWrt推荐用MacPorts来搭建MacOS中的相关工具。MacOS自带了gcc，版本信息如下：

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.4.0
Thread model: posix

如果安装了mp-gcc49，则会在/opt/local/bin目录下创建gcc，其版本信息如下：

gcc (MacPorts gcc49 4.9.2_1) 4.9.2
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

在搭建编译环境时，可能需要两个gcc切换（一个出错以后，切换另一个使用）。

首先，请确保安装了如下macports工具库

sudo port install coreutils e2fsprogs ossp-uuid asciidoc binutils bzip2 \
  fastjar flex getopt gtk2 intltool jikes hs-zlib openssl p5-extutils-makemaker \
  python26 subversion rsync ruby sdcc unzip gettext libxslt bison gawk \
  autoconf wget gmake ncurses findutils gnutar mpfr libmpc gcc49

checking for the correct version of the gmp/mpfr/mpc libraries... no
configure: error: Building GCC requires GMP 4.2+, MPFR 2.4.0+ and MPC 0.8.0+.
Try the --with-gmp, --with-mpfr and/or --with-mpc options to specify

问题描述

问题1：

Undefined symbols for architecture x86_64:
  "_iconv", referenced from:
      convert_using_iconv(void*, unsigned char const*, unsigned long, _cpp_strbuf*) in libcpp.a(charset.o)
     (maybe you meant: __Z14cpp_init_iconvP10cpp_reader, __cpp_destroy_iconv )
  "_iconv_close", referenced from:
      __cpp_destroy_iconv in libcpp.a(charset.o)
      __cpp_convert_input in libcpp.a(charset.o)
  "_iconv_open", referenced from:
      init_iconv_desc(cpp_reader*, char const*, char const*) in libcpp.a(charset.o)
ld: symbol(s) not found for architecture x86_64

碰到此种情况，说明你用的是mp-gcc49编译的，在这个地址有关于此错误的描述

http://stackoverflow.com/questions/12619600/libiconv-and-macos

macports的libiconv与mac系统的不一致，此时需要做如下修改：

1.切换到mac系统的gcc

2.进入staging_dir/host/usr，创建并进入lib目录，建立/opt/local/lib/中所有libiconv开头的符号链接

问题2：

Undefined symbols for architecture x86_64:
  "_ERR_remove_thread_state", referenced from:
      _rsa_sign in rsa-sign.o
ld: symbol(s) not found for architecture x86_64

这个问题最为奇怪，网上没有任何地方有对此问题的说明，经过仔细检查错误信息，发现在错误信息之前，有一个

HOSTLDFLAGS=“”

在mkimage的Makefile中，修改

#HOSTLDFLAGS="$(HOST_STATIC_LINKING)"
define Host/Compile
  -C $(HOST_BUILD_DIR) defconfig
  $(MAKE) -C $(HOST_BUILD_DIR) \
  HOSTLDFLAGS="-L/opt/local/lib" \
  tools-only
endef

实际上HOSTLDFLAGS在include/host-build.mk中定义：

ifneq ($(HOST_OS),Darwin)
  ifeq ($(CONFIG_BUILD_STATIC_TOOLS),y)
    HOST_STATIC_LINKING = -static
  endif
endi

ifneq ($(HOST_OS),Darwin)
  ifeq ($(CONFIG_BUILD_STATIC_TOOLS),y)
    HOST_STATIC_LINKING = -static
  endif
else
  HOST_STATIC_LINKING = -L/opt/local/lib
endif

总结

在第二个问题的处理上纠缠了很久。看来在MacOS下搭建OpenWrt的编译环境确实是一个比较“蛋疼”的举动