http://blog.csdn.net/shanleichicheng/article/details/7927971

ARM開發板上iconv_open("utf-8", "gb2312") 調用失敗的解決方法

應用程序代碼如下：

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("UTF-8", "GB2312", inbuf, inlen, outbuf, outlen);
}

開發環境為Ubuntu11.10,開發板為ARM開發板，交叉編譯器版本為arm-linux-4.4.3。相同的C源程序，在Ubuntu11.10上能夠正常執行，而在ARM開發板則不能正常執行，調用iconv_open("GB2312", "UTF-8") 返回失敗，錯誤信息為“Invalid argument”。經過查詢資料得知iconv相關函數為libc中的函數，初步分析得出結論為有可能是libc版本中iconv相關函數的版本不同造成的，因此要更新iconv相關函數。更新iconv相關函數有兩種方法：

第一，更新libc庫；

更新libiconv庫。

第一種方法更新libc庫比較麻煩，因為我們用的是編譯好的交叉編譯器，這中方法需要重新編譯生成交叉編譯器，并且也需要使用新編譯生成的交叉編譯工具重新編譯應用程序，因此本方法代價太大，采用第二種方法。

第二種方法為只更新libiconv庫，到iconv官網下載最新的庫源碼包，下載地址為:http://ftp.gnu.org/gnu/libiconv/libiconv-1.14.tar.gz；解壓后得到libiconv目錄，閱讀該目錄下Readme文件得出，編譯安裝libiconv庫也有兩種方式：

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開發板上采用“The libc plug/override mode”實驗成功，下面介紹編譯過程：

在libiconv目錄下：

$./configure --prefix=$PWD/out --host=arm-linux

$make

$make install

上述命令執行完成后會在libiconv目錄下生成新的out目錄，該目錄下存在4個目錄分別是：bin、 include、 lib、 share；在lib目錄下為生成的庫文件，其中一個為preloadable_libiconv.so，把它下載到開發板的lib目錄下，然后再設置開發板的系統環境變量：

$ export LD_PRELOAD=/lib/preloadable_libiconv.so

然后再執行應用程序即可，正常運行。

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