libcurl移植到android

一、总体概览

C库：libcurl 3.7

目标平台：android

编译平台：ubuntu 12

编译工具：ndk r7 or later

二、已知方法

1. 官网上给了两种方法，第一种方法是使用android源代码来一块编译，原文如下：

Method using the static makefile:

      see the build notes in the packages/Android/Android.mk file.

 Android.mk如下：

# Google Android makefile for curl and libcurl

#

# This file can be used when building curl using the full Android source

# release or the NDK. Most users do not want or need to do this; please

# instead read the Android section in docs/INSTALL for alternate

# methods.

#

# Place the curl source (including this makefile) into external/curl/ in the

# Android source tree.  Then build them with ‘make curl‘ or just ‘make libcurl‘

# from the Android root. Tested with Android versions 1.5, 2.1-2.3

#

# Note: you must first create a curl_config.h file by running configure in the

# Android environment. The only way I‘ve found to do this is tricky. Perform a

# normal Android build with libcurl in the source tree, providing the target

# "showcommands" to make. The build will eventually fail (because curl_config.h

# doesn‘t exist yet), but the compiler commands used to build curl will be

# shown. Now, from the external/curl/ directory, run curl‘s normal configure

# command with flags that match what Android itself uses. This will mean

# putting the compiler directory into the PATH, putting the -I, -isystem and

# -D options into CPPFLAGS, putting the -W, -m, -f, -O and -nostdlib options

# into CFLAGS, and putting the -Wl, -L and -l options into LIBS, along with the

# path to the files libgcc.a, crtbegin_dynamic.o, and ccrtend_android.o.

# Remember that the paths must be absolute since you will not be running

# configure from the same directory as the Android make.  The normal

# cross-compiler options must also be set. Note that the -c, -o, -MD and

# similar flags must not be set.

#

# To see all the LIBS options, you‘ll need to do the "showcommands" trick on an

# executable that‘s already buildable and watch what flags Android uses to link

# it (dhcpcd is a good choice to watch). You‘ll also want to add -L options to

# LIBS that point to the out/.../obj/lib/ and out/.../obj/system/lib/

# directories so that additional libraries can be found and used by curl.

#

# The end result will be a configure command that looks something like this

# (the environment variable A is set to the Android root path which makes the

# command shorter):

#

#  A=`realpath ../..` && \

#  PATH="$A/prebuilt/linux-x86/toolchain/arm-eabi-X/bin:$PATH" \

#  ./configure --host=arm-linux CC=arm-eabi-gcc \

#  CPPFLAGS="-I $A/system/core/include ..." \

#  CFLAGS="-nostdlib -fno-exceptions -Wno-multichar ..." \

#  LIBS="$A/prebuilt/linux-x86/toolchain/arm-eabi-X/lib/gcc/arm-eabi/X\

#  /interwork/libgcc.a ..."

#

# Finally, copy the file COPYING to NOTICE so that the curl license gets put

# into the right place (but see the note about this below).

3. 第二中方法使用 android ndk的脚本自己定制一套工具链，方便配置变量

Method using a configure cross-compile (tested with Android NDK r7c, r8):

      prepare the toolchain of the Android NDK for standalone use; this can be done by invoking the script:

        ./build/tools/make-standalone-toolchain.sh

     which creates a usual cross-compile toolchain. Lets assume that you put this toolchain below /opt then invoke configure with something like:

        export PATH=/opt/arm-linux-androideabi-4.4.3/bin:$PATH

        ./configure --host=arm-linux-androideabi [more configure options]

        make

三、自己方法

第一种方法需要用到android源代码，很不方便；第二种需要配置很多configure参数才能保证make成功。我的方法是结合了以上两种方法，用./configure得到curl_config.h等文件，然后使用ndk-build来编译Android.mk，而不是直接用make.

1. 搭建NDK环境：

1.1 下载NDK

官网下载页：http://developer.android.com/tools/sdk/ndk/index.html下载下来后，解压缩

注：下载符合你操作系统位数的ndk；还有就是下载ndk32的，因为android的64位支持没多久，大部分还都是32位的；版本越新越好，新版本会修复很多编译器bug，支持更多的语言特性。

1.2 配置NDK环境参数

打开 ~/.bashrc文件:

export NDK_HOME=~/Android /android-ndk-r8

export PATH=$PATH:$NDK_HOME

export PATH=$PATH:$NDK_HOME/toolchains/arm-linux-androideabi-4.6/prebuilt/linux/bin

测试一下

ndk-build –v

注1：修改环境变量的方法有三种，但是以上这种关机后不会失效：

    比如要把/etc/apache/bin目录添加到PATH中

1. #PATH=$PATH:/etc/apache/bin

　　使用这种方法,每当登出PATH就会恢复

　　2. #vi /etc/profile

　　在适当位置添加PATH=$PATH:/etc/apache/bin

　　这种方法最好,除非你强制手动修改PATH的值,否则将不会被改变

　　3. #vi ~/.bash_profile

　　修改PATH行,把/etc/apache/bin添加进去

　　这种方法是针对用户起作用的

注2：ndk-build使用有两种方法

1. cd ~/android-ndk-r9/samples/hello-jni/jni

       ndk-build

　　2. $NDK_HOME/ndk-build  -C ~/android-ndk-r9/samples/hello-jni/jni

        用 -C 指出工程目录路径

2.    配置和编译libcurl

2.1   下载源代码http://curl.haxx.se/download.html，解压

2.2   命令行进入curl目录后,执行

      ./configure –host=arm-linux-androideabi

      注：记住host一定是工具链前缀

2.3   把package/android/Android.mk修改一下，去掉后边的可执行文件相关的语句，我们只要生成静态库就行了。然后把package/android改为package/jni

      注：文件结构必须是jni/Android.mk，否则ndk-build找不到。

2.4   命令行进入package，执行ndk-build,大功告成。