ARM开发板上iconv_open("utf-8", "gb2312") 调用失败的解决方法
应用程序代码如下：
static int code_convert(char* from_charset, char* to_charset,
char* inbuf, size_t inlen, char* outbuf, size_t outlen)
{
iconv_t cd;
char **pin = &inbuf;
char **pout = &outbuf;
cd = iconv_open(to_charset, from_charset);
if (cd == -1)
{
perror("iconv_open:");
return -1;
}
memset(outbuf,0,outlen);
if (iconv(cd, pin, &inlen, pout, &outlen) == -1)
{
//printf("%s: call iconv failed!\n", __FUNCTION__);
printf("errno=%d\n", errno);
perror("iconv failed:\n");
iconv_close(cd);
return -1;
}
iconv_close(cd);
return 0;
}
static int g2u(char* inbuf, size_t inlen, char* outbuf, size_t outlen)
{
return code_convert("gb2312", "utf-8", inbuf, inlen, outbuf, outlen);
}
开发环境为Ubuntu11.10,开发板为ARM开发板，交叉编译器版本为arm-linux-4.4.3.
相同的C源程序，在ubuntu11.10上能够正常执行，而在ARM开发板则不能正常执行，调用
iconv_open("utf-8", "gb2312") 返回失败，错误信息为“Invalid argument”.
经过查询资料得知iconv相关函数为libc中的函数，初步分析得出结论为有可能是libc版本中
iconv相关函数的版本不同造成的，因此要更新iconv相关函数。
更新iconv相关函数有两种方法：
第一，更新libc库；
第二，更新libiconv库。
第一种方法更新libc库比较麻烦，因为我们用的是编译好的交叉编译器，这中方法需要重新编译生成
交叉编译器，并且也需要使用新编译生成的交叉编译工具重新编译应用程序，因此本方法代价太大，
采用第二种方法。
第二种方法为只更新libiconv库，到iconv官网下载最新的库源码包，下载地址为:
解压后得到libiconv目录，阅读该目录下Readme文件得出，编译安装libiconv库也有两种方式：
This library can be built and installed in two variants:
- The library mode. This works on all systems, and uses a library
`libiconv.so' and a header file `<iconv.h>'. (Both are installed
through "make install".)
To use it, simply #include <iconv.h> and use the functions.
To use it in an autoconfiguring package:
- If you don't use automake, append m4/iconv.m4 to your aclocal.m4
file.
- If you do use automake, add m4/iconv.m4 to your m4 macro repository.
- Add to the link command line of libraries and executables that use
the functions the placeholder @LIBICONV@ (or, if using libtool for
the link, @LTLIBICONV@). If you use automake, the right place for
these additions are the *_LDADD variables.
Note that 'iconv.m4' is also part of the GNU gettext package, which
installs it in /usr/local/share/aclocal/iconv.m4.
- The libc plug/override mode. This works on GNU/Linux, Solaris and OSF/1
systems only. It is a way to get good iconv support without having
glibc-2.1.
It installs a library `preloadable_libiconv.so'. This library can be used
with LD_PRELOAD, to override the iconv* functions present in the C library.
On GNU/Linux and Solaris:
$ export LD_PRELOAD=/usr/local/lib/preloadable_libiconv.so
On OSF/1:
$ export _RLD_LIST=/usr/local/lib/preloadable_libiconv.so:DEFAULT
A program's source need not be modified, the program need not even be
recompiled. Just set the LD_PRELOAD environment variable, that's it!
我在ARM开发板上采用“The libc plug/override mode”实验成功，下面介绍编译过程：
在libiconv目录下：
$./configure --prefix=$PWD/out --host=arm-linux
$make
$make install
上述命令执行完成后会在libiconv目录下生成新的out目录，该目录下存在4个目录分别是：
bin include lib share
在lib目录下为生成的库文件，其中一个为preloadable_libiconv.so，把它下载到开发板
的lib目录下，然后再设置开发板的系统环境变量：
$ export LD_PRELOAD=/lib/preloadable_libiconv.so
然后再执行应用程序即可，正常运行。