openwrt lede解决编译：error GNU libiconv not in use but included iconv.h is from libiconv
１．lede 17.1.5
2. 工程中没有glib2 需要手动添加一个，所以我从其他版本中直接拷贝过来一份glib2的配置（glib2 版本2.44.1）
3.当编译的时候出现了，error GNU libiconv not in use but included iconv.h is from libiconv
从源码找出现error的位置如下：
53
54 #if defined(USE_LIBICONV_GNU) && !defined (_LIBICONV_H)
55 #error GNU libiconv in use but included iconv.h not from libiconv
56 #endif
57 #if !defined(USE_LIBICONV_GNU) && defined (_LIBICONV_H) \
58 && !defined (__APPLE_CC__) && !defined (__LP_64__)
59 #error GNU libiconv not in use but included iconv.h is from libiconv
60 #endif
需要避免两种情况：
第一种： 需要满足 USE_LIBICONV_GNU ，即编译选项--with-libiconv=gnu (no/gnu/native)，且使用libiconv库
第二种： 需要满足即非USE_LIBICONV_GNU,即编译选项--with-libiconv=no, 且不使用libiconv库
下面来看我的glib2 Makefile:
1 #
2 # Copyright (C) 2007-2015 OpenWrt.org
3 #
4 # This is free software, licensed under the GNU General Public License v2.
5 # See /LICENSE for more information.
6 #
7
8 include $(TOPDIR)/rules.mk
9
10 PKG_NAME:=glib2
11 PKG_VERSION:=2.44.1
12 PKG_RELEASE:=1
13
14 PKG_SOURCE:=glib-$(PKG_VERSION).tar.xz
15 PKG_BUILD_DIR:=$(BUILD_DIR)/glib-$(PKG_VERSION)
16 PKG_SOURCE_URL:=@GNOME/glib/2.44
17 PKG_MD5SUM:=83efba4722a9674b97437d1d99af79db
18
19 PKG_BUILD_DEPENDS:=glib2/host libpthread zlib libintl libffi
20 HOST_BUILD_DEPENDS:=libintl/host libiconv/host libffi/host
21 PKG_INSTALL:=1
22 PKG_USE_MIPS16:=0
23
24 PKG_FIXUP:=autoreconf
25
26 HOST_BUILD_DIR:=$(BUILD_DIR_HOST)/glib-$(PKG_VERSION)
27
28 include $(INCLUDE_DIR)/host-build.mk
29 include $(INCLUDE_DIR)/package.mk
30 include $(INCLUDE_DIR)/nls.mk
31
32 define Package/glib2
33 SECTION:=libs
34 CATEGORY:=Libraries
35 DEPENDS:=$(ICONV_DEPENDS) $(INTL_DEPENDS) +zlib +libpthread +libffi +libattr
36 TITLE:=glib 2.0
37 MAINTAINER:=Peter Wagner
38 URL:=http://www.gtk.org/
39 endef
40
41 define Package/glib2/description
42 The GLib library of C routines
43 endef
44
45 HOST_CONFIGURE_ARGS += \
46 --disable-selinux
47
48 CONFIGURE_ARGS += \
49 --enable-shared \
50 --enable-static \
51 --enable-debug=no \
52 --disable-selinux \
53 --disable-fam \
54 $(if $(ICONV_FULL),--with-libiconv=gnu)
55
56 CONFIGURE_VARS += \
57 glib_cv_stack_grows=no \
58 glib_cv_uscore=no \
59 ac_cv_path_GLIB_GENMARSHAL=$(STAGING_DIR_HOST)/bin/glib-genmarshal \
60 ac_cv_func_mmap_fixed_mapped=yes \
61 ac_cv_func_posix_getpwuid_r=yes \
62 ac_cv_func_posix_getgrgid_r=yes
63
64 define Build/InstallDev
65 $(INSTALL_DIR) $(1)/usr/include
66 $(CP) \
67 $(PKG_INSTALL_DIR)/usr/include/glib-2.0 \
68 $(1)/usr/include/
69 $(CP) \
70 $(PKG_INSTALL_DIR)/usr/lib/glib-2.0/include/*.h \
71 $(1)/usr/include/glib-2.0/
72 $(CP) \
73 $(PKG_INSTALL_DIR)/usr/include/gio-unix-2.0 \
74 $(1)/usr/include/
75
76 $(INSTALL_DIR) $(1)/usr/lib
77 $(CP) \
78 $(PKG_INSTALL_DIR)/usr/lib/glib-2.0 \
79 $(1)/usr/lib/
80
81 $(CP) \
82 $(PKG_INSTALL_DIR)/usr/lib/*.{so*,a,la} \
83 $(1)/usr/lib/
84
85 $(INSTALL_DIR) $(1)/usr/lib/pkgconfig
86 $(INSTALL_DATA) \
87 $(PKG_INSTALL_DIR)/usr/lib/pkgconfig/*.pc \
88 $(1)/usr/lib/pkgconfig
89
90 $(INSTALL_DIR) $(2)/share/aclocal/
91 $(INSTALL_DATA) \
92 $(PKG_INSTALL_DIR)/usr/share/aclocal/*.m4 \
93 $(2)/share/aclocal/
94 endef
95
96 define Package/glib2/install
97 $(INSTALL_DIR) $(1)/usr/lib
98 $(CP) \
99 $(PKG_INSTALL_DIR)/usr/lib/*.so* \
100 $(1)/usr/lib/
101 endef
102
103 $(eval $(call HostBuild))
104 $(eval $(call BuildPackage,glib2)) 重点看：
48 CONFIGURE_ARGS += \
49 --enable-shared \
50 --enable-static \
51 --enable-debug=no \
52 --disable-selinux \
53 --disable-fam \
54 $(if $(ICONV_FULL),--with-libiconv=gnu)
ICONV_FULL 代表一个libiconv-full的库，如果这个库选上，使用--with-libiconv＝gnu选项
而ICONV_FULL怎么选：则看openwrt 目录中include/nls.mk
8 # iconv full
9 ifeq ($(CONFIG_BUILD_NLS),y)
10 ICONV_PREFIX:=$(STAGING_DIR)/usr/lib/libiconv-full
11 ICONV_FULL:=1
12
13 INTL_PREFIX:=$(STAGING_DIR)/usr/lib/libintl-full
14 INTL_FULL:=1
15
16 # iconv stub
17 else
18 ICONV_PREFIX:=$(STAGING_DIR)/usr/lib/libiconv-stub
19 ICONV_FULL:=
20
21 INTL_PREFIX:=$(STAGING_DIR)/usr/lib/libintl-stub
22 INTL_FULL:=
23 endif
从这个配置中可以看出，只需要选择编译选项CONFIG_BUILD_NLS即可．
make menuconfig
--->Global build settings
----->[*] Compile with full language support
另外还需要加上libiconv的库
---->Libraries
---------><*> libintl-full............................ GNU Internationalization library
保存配置，这样就大功告成了
这样的配置编译target是没有问题，我的工程在编译hostbuild的有问题，于是乎我在hostbuild中加了两项的配置：
45 HOST_CONFIGURE_ARGS += \
46 --disable-selinux \
47 --prefix=$(STAGING_DIR_HOST) \ //将生成的二进制，安装到host目录（我的工程默认安装，安装位置有问题）
48 --exec-prefix=$(STAGING_DIR_HOST) \
47 $(if $(ICONV_FULL),--with-libiconv=gnu) \ （host也有这个问题，所以也加上了）
48 ac_cv_path_GLIB_GENMARSHAL=$(STAGING_DIR_HOST)/bin/glib-genmarshal （这个如果不加，可能会找不到glib-genmarshal）
这要的改变，可以在工程完美编译通过．最终可以在:staging_dir/target****/usr/lib看到生成的glib2的库．
libiconv库 为需要做转换的应用提供了一个iconv()的函数，以实现一个字符编码到另一个字符编码的转换。