Thread: When should I use pragma pack?

When should I use pragma pack?

I found this code on some source files while other sources do not have the pragma pack()

Code:

#pragma pack (1)
typedef struct _net_ip_header_t {
	uint8 hdr_len:4;		// header length
	uint8 version:4;		// version
	uint8 tos;				// type of service
	uint16 tot_len;			// total length
	uint16 id;				// identification
	uint16 flags_offset;	// fragment offset field
	uint8 ttl;				// time to live
	uint8 proto;			// protocol
	uint16 cksum;			// checksum
	ip_addr src_ip;			// source ip address
	ip_addr dst_ip;			// destination ip address
} net_ip_header_t;
#pragma pack ()