C编程中良好的错误处理机制

main.c

#include ……

……
#ifdef ACR320_V3
#define PORT "Speaker"
#else
#define PORT "Headphone"
#endif

static char *command;

#if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95)
#define error(...) do {\
    fprintf(stderr, "%s: %s:%s:%d: ",command,__FILE__, __FUNCTION__, __LINE__); \
    fprintf(stderr, __VA_ARGS__); \
    putc('\n', stderr); \
} while (0)
#else
#define error(args...) do {\
    fprintf(stderr, "%s:%s:%s:%d: ",command,__FILE__, __FUNCTION__, __LINE__); \
    fprintf(stderr, ##args); \
    putc('\n', stderr); \
} while (0)
#endif

int volume_set(void)
{
    int err;
    snd_mixer_t *mixerFD;
    snd_mixer_elem_t *elem;
    Volume_t * p =  &v_state;
    command = "amixer";

    if((err = snd_mixer_open(&mixerFD,0))<0){
        error("Mixer %s open error: %s\n", PORT, snd_strerror(err));
        return err;
    }

    if((err = snd_mixer_attach(mixerFD,"default"))<0){
        error("Mixer %s attach error: %s\n", PORT, snd_strerror(err));
        snd_mixer_close(mixerFD);
        return err;
    }

    if((err = snd_mixer_selem_register(mixerFD,0,0))<0){ 
        error("Mixer %s register error: %s\n", PORT, snd_strerror(err));
        snd_mixer_close(mixerFD);
        return err;
    }

    if((err = snd_mixer_load(mixerFD))<0){
        error("Mixer %s load error: %s\n", PORT, snd_strerror(err));
        snd_mixer_close(mixerFD);
        return err;
    }
        for(elem=snd_mixer_first_elem(mixerFD);elem;elem=snd_mixer_elem_next(elem))

         {

                 if(snd_mixer_elem_get_type(elem)==SND_MIXER_ELEM_SIMPLE && snd_mixer_selem_is_active(elem))

                 {



                       if(!strcmp(PORT,snd_mixer_selem_get_name(elem)))

                       {

                           snd_mixer_selem_get_playback_volume_range(elem,&minVolume,&maxVolume);

                           snd_mixer_selem_get_playback_volume(elem,(snd_mixer_selem_channel_id_t)0,&Volume);

                           snd_mixer_selem_set_playback_switch(elem,(snd_mixer_selem_channel_id_t)0,(long)1);//设置不静音

                           snd_mixer_selem_set_playback_volume(elem,(snd_mixer_selem_channel_id_t)lr,volume);


                       }

                 }



            }

    snd_mixer_close(mixerFD);
    return 0;
}

error.c
#include
……
const char *snd_strerror(int errnum)
{
    if (errnum < 0)
        errnum = -errnum;
    if (errnum < SND_ERROR_BEGIN)
        return (const char *) strerror(errnum);
    errnum -= SND_ERROR_BEGIN;
    if ((unsigned int) errnum >= sizeof(snd_error_codes) / sizeof(const char *))
         return "Unknown error";
    return snd_error_codes[errnum];
}
……

string.h
……
extern char *strerror (int __errnum) __THROW;
……