有符号和无符号整数表达式S之间的比较

Question

I get this warning when compiling a source in c ++ with gcc in FreeBSD.

Could someone explain and help me solve the issue I'm having?

Following is a link to the entire source code, it was placed on pastebin because it contains 7000 lines of code. Source char.cpp

Here is the warning message :

In member function 'void CHARACTER::PointChange(BYTE, int, bool, bool)':

Answer 1

Expanding on @KaliG s answer:

On the line 3065 you are declaring: DWORD exp = GetExp();

Now what is a DWORD ? Well, it stands for double word , and a "word" is 16 bits on this C++ implementation (Win32). It is a typedef and is actually an unsigned integer . http://en.wikipedia.org/wiki/Word_%28computer_architecture%29

The other variable, amount is an argument defined as the type (signed) int .

So you are comparing a signed and unsigned integer - which causes the warning. You can solve this by simply casting amount to an unsigned int (or "DWORD") since you have verified already that it is in fact positive.

So change the line to:

if (amount < 0 && exp < (DWORD) -amount)

This should work - but I have no idea how your method works other than that.

Sidenote: Hungarian notation is really ghastly stuff - so you should really dig into what the different type names they use actually are. http://en.wikipedia.org/wiki/Hungarian_notation

Sidenote 2: Don't use ALLCAPS class names... developers are used to think that those identifiers are constants, so you confuse other people who might read your code.

Sidenote 3: Read up on 2s complement to understand what the ALU ( http://en.wikipedia.org/wiki/Arithmetic_logic_unit ) inside the CPU is actually doing: http://en.wikipedia.org/wiki/Two%27s_complement

Answer 2

From the error thrown, I would say it is because 'exp' is either an unsigned or signed variable while 'amount' is the opposite, hence the reason you get the comparison error thrown.

Please post the lines of code where you declare these variables. :)

(Verify if you declared either of these 2 variables as a signed/unsigned by mistake.)