iconv_open

mrjbydd 2013-09-04

展開全文

ARM開發(fā)板上iconv_open("utf-8", "gb2312") 調(diào)用失敗的解決方法

應(yīng)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("gb2312", "utf-8", inbuf, inlen, outbuf, outlen);
}

開發(fā)環(huán)境為Ubuntu11.10,開發(fā)板為ARM開發(fā)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(zhí)行，而在ARM開發(fā)板則不能正常執(zhí)行，調(diào)用
iconv_open("utf-8", "gb2312") 返回失敗，錯誤信息為“Invalid argument”.
經(jīng)過查詢資料得知iconv相關(guān)函數(shù)為libc中的函數(shù)，初步分析得出結(jié)論為有可能是libc版本中
iconv相關(guān)函數(shù)的版本不同造成的，因此要更新iconv相關(guān)函數(shù)。
更新iconv相關(guān)函數(shù)有兩種方法：
第一，更新libc庫；
第二，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(yīng)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(wǎng)下載最新的庫源碼包，下載地址為:
http://ftp./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(fā)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(zhí)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(fā)板
的lib目錄下，然后再設(shè)置開發(fā)板的系統(tǒng)環(huán)境變量：
$ export LD_PRELOAD=/lib/preloadable_libiconv.so

然后再執(zhí)行應(yīng)用程序即可，正常運行。