error C2678

_Flaviu

I've met a weird error:

error C2678: binary '|=' : no operator found which takes a left-hand operand of type 'FILE_ATTR_FLAGS' (or there is no acceptable conversion)

1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\propsys.h(703): could be 'GETPROPERTYSTOREFLAGS &operator |=(GETPROPERTYSTOREFLAGS &,GETPROPERTYSTOREFLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\propsys.h(1685): or 'PROPDESC_TYPE_FLAGS &operator |=(PROPDESC_TYPE_FLAGS &,PROPDESC_TYPE_FLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\propsys.h(1704): or 'PROPDESC_VIEW_FLAGS &operator |=(PROPDESC_VIEW_FLAGS &,PROPDESC_VIEW_FLAGS)'
........
........
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\shobjidl.h(31763): or 'HOMEGROUPSHARINGCHOICES &operator |=(HOMEGROUPSHARINGCHOICES &,HOMEGROUPSHARINGCHOICES)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\shobjidl.h(32037): or 'LIBRARYOPTIONFLAGS &operator |=(LIBRARYOPTIONFLAGS &,LIBRARYOPTIONFLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\shobjidl.h(32052): or 'LIBRARYSAVEFLAGS &operator |=(LIBRARYSAVEFLAGS &,LIBRARYSAVEFLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\shobjidl.h(32793): or 'LIBRARYMANAGEDIALOGOPTIONS &operator |=(LIBRARYMANAGEDIALOGOPTIONS &,LIBRARYMANAGEDIALOGOPTIONS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\thumbcache.h(119): or 'WTS_FLAGS &operator |=(WTS_FLAGS &,WTS_FLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\thumbcache.h(127): or 'WTS_CACHEFLAGS &operator |=(WTS_CACHEFLAGS &,WTS_CACHEFLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\shlobj.h(542): or 'SHELL_LINK_DATA_FLAGS &operator |=(SHELL_LINK_DATA_FLAGS &,SHELL_LINK_DATA_FLAGS)'
1> c:\program files (x86)\microsoft sdks\windows\v7.0a\include\shlobj.h(1394): or 'KNOWN_FOLDER_FLAG &operator |=(KNOWN_FOLDER_FLAG &,KNOWN_FOLDER_FLAG)'
1> while trying to match the argument list '(FILE_FLAGS, FILE_FLAGS)'

Here is the code that generate the error:

sc->flags |= flag;

where flag is FILE_FLAGS, and sc->flags is

struct scr {
....
....
FILE_FLAGS flags;
....
};

Now, of course that I'ave tried:

scr& operator|=(const scr& rhs)
{
	return \*this;
}

but this err

Lost User

Where is FILE_FLAGS defined? IN your code, or in a system header?

_Flaviu

Is defined inside of one of my code header:

typedef enum {
FILE_READONLY = 0x00000001,
FILE_HIDDEN = 0x00000002,
FILE_SYSTEM = 0x00000004,

FILE\_DIRECTORY = 0x00000010,
FILE\_ARCHIVE = 0x00000020,
FILE\_DEVICE = 0x00000040,
FILE\_NORMAL = 0x00000080,

FILE\_TEMPORARY = 0x00000100,

....
.....

}FILE_FLAGS;

Lost User

This works but is not really correct.

sc->flags = FILE_FLAGS(sc->flags | flag);

I suspect the issue is that enums are usually used to signify single values, i.e the flags field is either FILE_READONLY or FILE_SYSTEM, but not both. If you need to combine values then you should really use a set of #define statements.

_Flaviu

Thank you Richard, that error has vanished, but I cannot try this code yet ... why do you say that this solution is not really correct ? The safe solution would be to overload |= operator, but I cannot do that into enum, right ?

Lost User

_Flaviu wrote:

why do you say that this solution is not really correct ?

Because, as I mentioned before, enums are used to indicate a set of possible values for an item. For example a class of type Car could contain an enum that indicates the manufacturer, such that the enum definition is:

enum manufacturer
{
AUDI = 1,
BMW,
DAIMLER,
MERCEDES,
// etc.
}

And you would never combine thos values in the car type variable. So, in your case you should use #define statements, which the compiler will be happy with.

_Flaviu

But this enum is not a part of any struct or class, is just defined into a header file, along with other several enum's ... and this enum has a lot of values, that is why I intend to avoid to translated as #define's ... I don't know what to do ...

Lost User

But the issue is, as I keep repeating, that this is not the correct way to use enums. If you want to combine flag values then use #define, if you want to select one value from a set then use enum. That is the rule for C and C++, and that is why the compiler complains about your code.

_Flaviu

Thank you Richard for your patience. BTW, is a legacy code, is not written by me. There will be more suitable to chnage this enum to a struct and where to overload |= operator ?

Lost User

Why would you change it to a struct, it only requires a single integer variable to hold all the flags.

int flags = FILE_READONLY | FILE_HIDDEN;
flags |= FILE_SYSTEM;

_Flaviu

So the finest solution is to take these values from enum and put them as #defines. I will do this change.

_Flaviu

I am afraid that I cannot change that enum into #defines, because I have:

na->flags |= flag;

where

FILE_FLAGS flag;

and na is struct level1, and inside this level1 struct, I have

struct level1
{
FILE_FLAGS flags;
....
};

I have entered in some deadlock ? Please help me to solve this error ...

Victor Nijegorodov

Try to declare both flags and flag as int

_Flaviu

Yes, but FILE_FLAGS is enum with int values ...

Victor Nijegorodov

Then, as Richard already suggested replace this enum with a set of #define.

_Flaviu

Agree, but that enum is a part of another struct ... so, how can I put as part of a struct several #defines ?

Lost User

Of course you can change it to #defines. The definition of FILE_FLAGS then becomes an int type. And then the rest of the code should compile correctly.

_Flaviu

I am not get something, so forgive me. I have moved those enum values as #defines, but of course, now I get error from struct: doesn't know who is FILE_FLAGS flags; from level1 struct.

/*
typedef enum {
FILE_READONLY = 0x00000001,
FILE_HIDDEN = 0x00000002,
FILE_SYSTEM = 0x00000004,

FILE\_DIRECTORY = 0x00000010,
FILE\_ARCHIVE = 0x00000020,
FILE\_DEVICE = 0x00000040,
FILE\_NORMAL = 0x00000080,

FILE\_TEMPORARY = 0x00000100,

....
.....

}FILE_FLAGS;
*/

#define FILE_READONLY = 0x00000001
#define FILE_HIDDEN = 0x00000002
#define FILE_SYSTEM = 0x00000004

of course, FILE_FLAGS enum has disappeared ... obviously, I don't understood something ... but what ?

struct level1
{
FILE_FLAGS flags; // <-- error
....
};

Victor Nijegorodov

_Flaviu wrote:

struct level1 { FILE_FLAGS flags; // <-- error .... };

Try

struct level1
{
int flags; // <-- error
....
};

_Flaviu

Ok, but even flag is comming as function parameter, just like this:

static void SomeFunction(level1* na, FILE_FLAGS flag)
{
....
na->flags |= ~flag;
....
}

So, I guess I cannot give up FILE_FLAGS enum ... don't I ?