Suggest edit — casting

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---
title: "casting"
type: concept
source: https://www.jemoka.com/posts/kbhcasting/
confidence: high
status: active
---

Pitfalls The bytes remains the same despite copying, so you can get too funky:
int v = -12345; unsigned int uv = v; printf(&#34;v = %d, uv = %d\n&#34;, v, uv); This prints &ldquo;v = -12345, uv=4294954951&rdquo;. As in: when you copy rvalues, the bit pattern gets copied and not the numerical number itself; so, it will overflow.
You can use U to force an signed quantity to be unsigned:
unsigned int uv = -12345U; sign promotion If you have the nerve of putting a comparing things of different types (don&rsquo;t), then, the signed quantities gets promoted to be unsigned.
That is, we get that:
-1 &lt; 0U is false because the -1 is promoted to an unsigned integer 2&hellip;.7 &gt; -2&hellip;.7 is true because nothing is converted type size promotion If you have the nerve of putting a comparing things of different types (don&rsquo;t), then, the smaller types get promoted to being a bigger types.
casting from small unsigned value to larger unsigned value just requires us prepending a buncha zeros as needed casting from a small signed value to larger signed value requires us repeating the left most value to fill out the rest of the variable (-1 = 11111, so bigger -1 = 11111 (repeated) 111) lasting from a large value to a smaller value will cause truncation type size truncation Take, for instance:
int x = 53191; short sx = x; int y = sx; The short is 2 byte, which means that 2 of the left bytes of the int got dropped.