Header file compilation

[Mikael S. H.]

Header file compilation

I'm coding a small irc bot, and I've noticed that compilation takes very
long when I add certain header files (compared to compilation time without).

I've tried to find out if it is possible to compile a header file, yet I
have only found that it is possible, but not how it is done.

I have RTFM, STFW and searched USENET, yet I have only found a document
saying "just write `g++ file.h`, and it'll work".

Thanks in advance
Mikael S. Hoilund

[Victor Bazarov]

Mikael S. H. wrote:

Header file compilation

I'm coding a small irc bot, and I've noticed that compilation takes very
long when I add certain header files (compared to compilation time
without).

I've tried to find out if it is possible to compile a header file, yet I
have only found that it is possible, but not how it is done.

I have RTFM, STFW and searched USENET, yet I have only found a document
saying "just write `g++ file.h`, and it'll work".

The only meaningful way to "compile" a header is to have a small source
file that consists of a single preprocessor instruction:

#include <yourheader>

or

#include "yourheader "

(don't forget to end the line with the newline character). Then you
compile that source file.

V

[mlimber]

Mikael S. H. wrote:

Header file compilation

I'm coding a small irc bot, and I've noticed that compilation takes very
long when I add certain header files (compared to compilation time without).

I've tried to find out if it is possible to compile a header file, yet I
have only found that it is possible, but not how it is done.

I have RTFM, STFW and searched USENET, yet I have only found a document
saying "just write `g++ file.h`, and it'll work".

Thanks in advance
Mikael S. Hoilund

Header files (.h, .hpp, etc.) are quite litterally *included* in the
source file in which they are #included (headers, or .cc, .cpp, etc.).
You don't compile them separately because they are intended to share
information (types, constants, global variables, function prototypes,
class definitions, templates, etc.) needed across source files and
shouldn't have any useful compiler output by themselves.

So, if you don't need the information in that header file, then don't
include it. If you do, then you can deal with the long compile times or
try to reduce amount of information pulled in (e.g., if your header
includes ten others, but you only need one of those, just include that
one header).

Or you can be more specific by showing us some code.

Cheers! --M

[Thomas Tutone]

Mikael S. H. wrote:

Header file compilation

I'm coding a small irc bot, and I've noticed that compilation takes very
long when I add certain header files (compared to compilation time without).

I've tried to find out if it is possible to compile a header file, yet I
have only found that it is possible, but not how it is done.

I have RTFM, STFW and searched USENET, yet I have only found a document
saying "just write `g++ file.h`, and it'll work".

This is an implementation-specific question. Many compilers include a
pre-compiled header option. gcc, for example, lets you pre-compile a
header file in exactly the way you describe. Other implementations , if
they offer pre-compiled headers, may do so in a different way. If you
are in fact using gcc, consult the gcc manual, which has a section on
pre-compiled headers:

http://gcc.gnu.org/onlinedocs/gcc-4....mpiled-Headers

Best regards,

Tom

[Mikael S. H.]

Thomas Tutone wrote:

Mikael S. H. wrote:

I've tried to find out if it is possible to compile a header file, yet I
have only found that it is possible, but not how it is done.

This is an implementation-specific question. Many compilers include a
pre-compiled header option. gcc, for example, lets you pre-compile a
header file in exactly the way you describe. Other implementations , if
they offer pre-compiled headers, may do so in a different way. If you
are in fact using gcc, consult the gcc manual, which has a section on
pre-compiled headers:

http://gcc.gnu.org/onlinedocs/gcc-4....mpiled-Headers

Hm, I think that was exactly the document I stumbled upon. However, I
seem to be unable to put those instructions into practice. When I try to
compile it without -x, it says "compilatio n of header file requested".
When I try it with -x, it says "undefined reference to main".

And I'm sorry about the off topic post, but apparently my ISP is linux
hostile, since I can't get to a single linux related newsgroup.

Thanks
Mikael S. Hoilund

[Victor Bazarov]

Mikael S. H. wrote:

Thomas Tutone wrote:

Mikael S. H. wrote:

I've tried to find out if it is possible to compile a header file, yet I
have only found that it is possible, but not how it is done.

This is an implementation-specific question. Many compilers include a
pre-compiled header option. gcc, for example, lets you pre-compile a
header file in exactly the way you describe. Other implementations , if
they offer pre-compiled headers, may do so in a different way. If you
are in fact using gcc, consult the gcc manual, which has a section on
pre-compiled headers:

http://gcc.gnu.org/onlinedocs/gcc-4....mpiled-Headers

Hm, I think that was exactly the document I stumbled upon. However, I
seem to be unable to put those instructions into practice. When I try to
compile it without -x, it says "compilatio n of header file requested".
When I try it with -x, it says "undefined reference to main".

Add -c (to compile only, no link).
And I'm sorry about the off topic post, but apparently my ISP is linux
hostile, since I can't get to a single linux related newsgroup.

Use Google Groups.

V