RE: [lwip-devel] Port on 16 bits processor: problem in ip4_addr_netmask_valid() function

[Bill Auerbach]

Yes, the U is needed.  ANSI C defaults to type signed int for Hex constants unless the constant won’t fit in a signed int.  Chances are in C if you use 0x you intended an unsigned value and the U needs to be explicitly added in those cases.

 

Bill

 

In def.h:

  #define PP_HTONS(x) ((((x) & 0xff) << 8) | (((x) & 0xff00) >> 8))

In ip.h:

  #define IP_OFFMASK 0x1fff   /* mask for fragmenting bits */

  #define IP_MF 0x2000        /* more fragments flag */

 

I think IP_OFFMASK and IP_MF (and others) should be declared unsigned ('U' suffix), otherwise the left shifting by 8 positions can could wrong for a signed int.

 

What do you think?