小编ris*_*ess的帖子

我正在使用为此平台构建的工具链（MIPS openwrt）将ffmpeg源交叉编译为mips-openwrt目标。

然后，ffmpeg make在uclibc头文件stdlib.h中给出以下错误，如下所示：

In file included from ./libavutil/avassert.h:30:0,
                 from libavfilter/avfilter.c:23:
/home/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/gcc/mips-openwrt-linux-uclibc/4.6.3/../../../../mips-openwrt-linux-uclibc/sys-include/stdlib.h:546:14: error: expected identifier or '(' before 'void'
/home/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/gcc/mips-openwrt-linux-uclibc/4.6.3/../../../../mips-openwrt-linux-uclibc/sys-include/stdlib.h:546:14: error: expected ')' before numeric constant

来自该行号的uclibc stdlib.h中的代码是

    #ifdef __USE_ISOC99
    __BEGIN_NAMESPACE_C99
    /* Terminate the program with STATUS without calling any of the
       functions registered with `atexit' or `on_exit'.  */
    extern void _Exit (int __status) __THROW __attribute__ ((__noreturn__));
    __END_NAMESPACE_C99
    #endif

   __BEGIN_NAMESPACE_STD
   /* Return the value of envariable NAME, or NULL if it doesn't exist.  */
   extern char *getenv (__const char …

我想知道如何确定我的元组是否为空？请注意,我将std :: tuble与std :: map结合使用,如下所示:

typedef std::tuple<SDESType,INT32,std::string> SDesItem;
typedef std::map<SDESType,SDesItem> SDesItemMap;

现在我想检查第二个值SDesItemMap,即元组是否为空？

if(SDesItems[SDESType] != NULL) // this is error