what does x =!x means?

Question

While readinf MuPDF comes across the source code line

x = !x;

Want to know what does the above code do?

While compilation is also gives error as

assuming signed overflow does not occur when simplifying 
condition to constant [-Werror=strict-overflow ]

Are you sure the diagnostic is related to this statement? Can you remove it, compile and then put it back again and compile to confirm? — ouah, Jan 25 '15 at 18:25

juanchopanza · Accepted Answer · 2015-01-25T18:33:39.557

6

!x will evaluate to either 0 or 1, depending on the value of x.

edited Jan 25 '15 at 18:33

answered Jan 25 '15 at 18:18

juanchopanza

1

I don't get that error. The corresponding warning is supposed to be enabled with `-Wall` in gcc and I guess by extension in clang. I don't see the error with the latter. You should post an MCVE that reproduces the error. – juanchopanza Jan 25 '15 at 18:32
Use flag strict-overflow – Vineet1982 Jan 25 '15 at 20:36
@Vineet1982 I already tried. No error. Why not post the MCVE? – juanchopanza Jan 25 '15 at 20:40

score 1 · Answer 2 · answered Jan 25 '15 at 18:19

1

Assuming x is boolean, this sets x false if it is true, and true if it is false.

answered Jan 25 '15 at 18:19

Phil Lello

2 Answers2