Wireshark-dev: Re: [Wireshark-dev] Problem with recommended Makefile.nmake
From: Guy Harris <[email protected]>
Date: Thu, 14 Jul 2011 11:19:17 -0700
On Jul 14, 2011, at 11:00 AM, Ed Beroset wrote:

> The error messages say:
> packet-myudp.c(90) : error C2220: warning treated as error - no 'object' file generated

What the errors mean:

> packet-myudp.c(90) : warning C4554: '<<' : check operator precedence for possible error; use parentheses to clarify precedence

The expression is valid, but it might not do what you think it does.  The rules for C operator precedence (they're the same in C++) are:

	http://www.difranco.net/cop2220/op-prec.htm

and those are the rules the C compiler will follow.  If that means that code isn't doing what you want, add parentheses to tell the compiler what you want.

> packet-myudp.c(782) : warning C4113: 'void (__cdecl *)()' differs in parameter lists from 'void (__cdecl *)(void)'

In C, a function declaration such as

	void func();

means "a function that can be passed an arbitrary list of arguments", not "a function that takes no arguments", and the same applies to function definitions.  This is for historical reasons, as C originally didn't include a declaration of the function argument list in function definitions or declarations; use

	void func(void);

instead.

> packet-myudp.c(1119) : warning C4244: '=' : conversion from 'double' to 'gfloat', possible loss of data
> packet-myudp.c(1219) : warning C4244: '=' : conversion from 'double' to 'gfloat', possible loss of data
> packet-myudp.c(1860) : warning C4244: '=' : conversion from 'double' to 'gfloat', possible loss of data

Unless you really only care about single precision, you should probably use gdouble rather than gfloat.  (If you really do want to throw out about half the precision bits, explicitly cast the "double"-valued expression to gfloat.)

> packet-myudp.c(2134) : warning C4244: '=' : conversion from 'guint16' to 'guint8', possible loss of data

Unless the guint16 is guaranteed to have its upper 8 bits zero, you probably want to use a guint16 rather than a guint8.

> The difference in the makefiles is that you don't have the "warnings treated as error" turned on in the modified file, but that's not the correct modification to make.  The correct way to address this is to fix the warnings in packet-myudp.c as pointed out by the compiler.  They look like mostly minor things that would only need a few minutes to address and your code will be better quality as a result even though it may work as intended already.

Exactly.