c - difference between 2 different implementations of declaring structures -

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gcc 4.4.4 c89

i wondering real difference between following 2 implementations of defining structures?

channel.h file  struct channel_tag;  struct channel_tag* init_channel(size_t channel_id); void dispose_channels(struct channel_tag *channel);  channel.c file  typedef struct channel_tag {     size_t channel_id; } channel_t;

=================== second implemenation ===============

channel.h file  typedef struct channel_tag channel;  channel* init_channel(size_t channel_id); void dispose_channels(channel *channel);  channel.c file  struct channel_tag {     size_t channel_id; };

many suggestions,

in first case have 1 data type, , second have 2 (where 2nd typedef'ed first). there no difference in generated code. many people more convenient read/write code omits struct keyword.


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