Where does the C standard describe overflow of signed integers?

[Nathan Sidwell]

Nicholas Nethercote wrote:
> Hi,
> 
> There was recently a very long thread about the overflow behaviour of 
> signed integers in C.  Apparently this is undefined according to the C 
> standard.  I searched the standard on this matter, and while I did find 
> some paragraphs that described how unsigned integers must wrap around 
> upon overflow, I couldn't find anything explicit about signed integers.  
> Can someone point me to the relevant part(s) of the standard?

c99 6.5 para 5 (overflow is undefined) & 6.3.1.3 (conversions to unsigned type 
obey modulo laws)

c++ 5 para 5 (overflow is undefined, unless otherwise stated) & 3.9.1 para 4 
(unsigned types obey modulo laws)

I cannot find, in c99, a statement that all unsigned arithmetic obeys modulo 
laws -- only that integral conversions to them do.

nathan

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