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I got warning:
Pe186 "Pointless comparison of unsigned int with zero"
when I tried to compile the following code:
for(clLoop = cpLoopStart; clLoop >= 0; clLoop--) { //Do something } I don't understand why. I could understand, if I were looking for a value less than zero, since an unsigned int can never be negative. But all I am looking for here is if it is equal to zero, which an unsigned int certainly can be.
I could even see this error if in this loop I tried to pre-decrement instead of post-decrement, but again that is not the case.
539
Unsigned Integers (often called "uints") are just like integers (whole numbers) but have the property that they don't have a + or - sign associated with them. Thus they are always non-negative (zero or positive). We use uint's when we know the value we are counting will always be non-negative.
Yes, it does matter. On a platform with 32bit int with e.g. int x = -1; unsigned y = 0xffffffff; the expression x == y would yield 1 because through the "usual arithmetic conversions" the value of x is converted to unsigned and thus to 0xffffffff .
The Google C++ style guide recommends avoiding unsigned integers except in situations that definitely require it (for example: file formats often store sizes in uint32_t or uint64_t -- no point in wasting a signedness bit that will never be used).
An unsigned variable type of int can hold zero and positive numbers, and a signed int holds negative, zero and positive numbers. In 32-bit integers, an unsigned integer has a range of 0 to 232-1 = 0 to 4,294,967,295 or about 4 billion.
You check whether the unsigned int is greater than or equal (>=) zero. This expression will always be true, because unsigned integers will never be less than zero.
The compiler tries to warn you that you are about to program an infinite loop.
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