How to Cross-Compile libiconv for Android

If your legacy C/C++ code includes <iconv.h> to convert the encoding of characters from one coded character set to another, and you need to cross-compile it with the Android NDK, you will get the following error:

   error: iconv.h: No such file or directory

In fact there is currently no iconv.h available in the Android NDK and you will have to port libiconv to Android yourself.
I successfully used the following instructions to cross-compile libiconv.so for Android.

Get the source code for libconv-1.13.1:

   $ wget http://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.13.1.tar.gz

Unzip and untar the file:

   $ tar zxvf libiconv-1.13.1.tar.gz

Patch libcharset.c using the following patch file (or else you will get another error: : langinfo.h: No such file or directory) :

   $ echo "diff --ignore-file-name-case -wuprN libiconv-1.13.1.orig/libcharset/lib/localcharset.c libiconv-1.13.1/libcharset/lib/localcharset.c
--- libiconv-1.13.1.orig/libcharset/lib/localcharset.c  2009-06-21 07:17:33.000000000 -0400
+++ libiconv-1.13.1/libcharset/lib/localcharset.c       2012-12-18 10:20:27.000000000 -0500
@@ -44,7 +44,7 @@
 # endif
 #endif

-#if !defined WIN32_NATIVE
+#if !defined(WIN32_NATIVE) && !defined(__ANDROID__)
 # if HAVE_LANGINFO_CODESET
 #  include <langinfo.h>
 # else
@@ -328,7 +328,7 @@ locale_charset (void)
   const char *codeset;
   const char *aliases;

-#if !(defined WIN32_NATIVE || defined OS2)
+#if !(defined WIN32_NATIVE || defined OS2 || defined __ANDROID__)

 # if HAVE_LANGINFO_CODESET " > iconv.patch

   $ patch -b -p0 < ./iconv.patch

Run the configure script and generate iconv.h:

   $ cd libiconv-1.13.1
   $ ./configure

Create a jni sub-directory:

$ mkdir jni

And save the following lines in jni/Android.mk:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
TARGET_ARCH_ABI := armeabi-v7a
LOCAL_MODULE    := iconv
LOCAL_CFLAGS    := \
    -Wno-multichar \
    -D_ANDROID \
    -DLIBDIR="\"c\"" \
    -DBUILDING_LIBICONV \
    -DIN_LIBRARY
LOCAL_C_INCLUDES := \
    ../libiconv-1.13.1 \
    ../libiconv-1.13.1/include \
    ../libiconv-1.13.1/lib \
    ../libiconv-1.13.1/libcharset/include
LOCAL_SRC_FILES := \
    ../libiconv-1.13.1/lib/iconv.c \
    ../libiconv-1.13.1/lib/relocatable.c \
    ../libiconv-1.13.1/libcharset/lib/localcharset.c
include $(BUILD_SHARED_LIBRARY)

Finally cross-compile iconv using the ndk-build tool:

   $ cd jni
   $ ndk-build V=1

If everything goes well, you will find iconv.h under libiconv-1.13.1/include and libiconv.so under libs/armeabi.