.cpp and .h

**cyberfish** · 07-02-2008

I think it's MSVC specific.

How about just randomly spam some letters on the keyboard

. Or use a pseudo random number generator while you are at it.

**laserlight** · 07-02-2008

But then what happens if you have two include files with the same name in different directories?

The obvious solution that keeps in line with dwks' suggestion is DIRECTORY_HEADER_H. I have used NAMESPACE_CLASS_H, though I suppose FILENAME_H_MONTH_DAY_YEAR works well too.

**cyberfish** · 07-02-2008

Is there anything wrong with just using a random number? I actually wasn't joking

.

**laserlight** · 07-02-2008

Is there anything wrong with just using a random number?

I do not think so, other than that it could be troublesome since the probability of having duplicate names is rather small anyway, especially when things like namespace names, directory names, or the current date is added in, and these can come to mind immediately.

**CornedBee** · 07-03-2008

I think she means prefix.

For example, I call my files PROJECT_PATH_TO_FILENAME_SR_H

The SR_H suffix is personal for me and should guarantee that my guards never collide with those of other people (unless they have the initials S.R. too).

#ifndef IOCHAIN_INFRASTRUCTURE_CHAIN_HPP_SR_H

**Elysia** · 07-03-2008

Perhaps you mean creation date, cpjust? It didn't occur to me right away, but I guess that's one way of doing it.
I was thinking of some directory directive, like the way OS separates files.
C:\foo\x.h
and
c:\x.h
wouldn't be the same.

**cpjust** · 07-03-2008

Originally Posted by Elysia

Perhaps you mean creation date, cpjust? It didn't occur to me right away, but I guess that's one way of doing it.
I was thinking of some directory directive, like the way OS separates files.
C:\foo\x.h
and
c:\x.h
wouldn't be the same.

Yes, the MONTH_DAY_YEAR part is the date when you first create the header file. You could also throw in the HOUR_MIN_SECOND if you really want, but I don't usually create that many header files on the same day.

**abachler** · 07-03-2008

I generally use COMPANYINITIALS_HEADERNAME, since it is unlikely that it will collide with a header of someone else at the company while im here, and what happens after isnt my responsibility.

**CornedBee** · 07-03-2008

Originally Posted by cpjust

Yes, the MONTH_DAY_YEAR part is the date when you first create the header file. You could also throw in the HOUR_MIN_SECOND if you really want, but I don't usually create that many header files on the same day.

I do, in the initial phase of development. That's when I'm writing the rough interfaces, and that means many, many headers created in a single day.

**dwks** · 07-04-2008

In a project that made use of xuni, I accidentally created a header file called "graphics.h" -- which xuni also has. Both were using GRAPHICS_H for the inclusion guard. So now all of xuni's header files have guards like XUNI_GUARD_GRAPHICS_H.

It took me quite a while to figure out what was wrong. Inclusion guards aren't supposed to fail.

So I can see why someone might want to put a random number or other unique string inside them . . . .

**Magos** · 07-04-2008

Or simply use #pragma once. Though not standard, according to wikipedia it's "widely supported", "without possibility for name clashes" and "increased compilation speed".

**dwks** · 07-04-2008

Yes, apparently even GCC supports it, though it's "deprecated". (I'm assuming MSVC does too; it likes #pragmas.)

On the other hand, apparently it doesn't always work, while inclusion guards do.
http://groups.google.com/group/comp....279780c364628f

**Elysia** · 07-04-2008

Microsoft's #pragma once doesn't help with collisions, however. I found out that the hard way.

**dwks** · 07-04-2008

So what is it good for then? Does it "speed up compile times" or something?

**Elysia** · 07-04-2008

According to microsoft's documentation, it makes the compiler open each file once, speeding up compile times.

Originally Posted by MSDN

Specifies that the file will be included (opened) only once by the compiler when compiling a source code file.

Remarks
This can reduce build times as the compiler will not open and read the file after the first #include of the module.