Re: [PATCH] Re: sscanf("-1", "%d", &i) fails, returns 0

[Andreas Schwab <schwab@suse.de>]

"Randy.Dunlap" <rddunlap@osdl.org> writes:

|> Andreas Schwab wrote:
|> |> IOW, asking for an unsigned number (in the format string)
|> |> and getting "-123" does return 0.
|> 
|> | Not in C.  According to the standard scanf is supposed to convert the
|> | value to unsinged and return that.
|> OK, thanks, I found that in the C spec.
|> 
|> Now what does it mean to "convert the value to an unsigned and return
|> that."  This is the same as above, isn't it?
|> I.e., on the scanf() side, there is no conversion needed; just store the
|> value.

The C standard also supports ones-complement and sign-magnitude
representation of signed integers where signed<->unsigned conversion is a
non-trivial operation in the sense that the bit representation does
change.  And scanf knows the signedness of the destination due to the
format spec.

Andreas.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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