detect necessary #includes

**Logan Shaw** · Jan 14 '06, 08:35 AM

Re: detect necessary #includes

Steven Woody wrote:[color=blue]
> hi,
>
> after some weeks of development of a project, there likely are many
> "#include" in source files which was added before but are now
> unnecessary. is there any tool which can find out those "#include"s
> and tell me it's safe to remove them? manual work is so time consuming.[/color]

Only a standards document or other API documentation can really tell
you whether it's safe to remove a #include.

Consider what happens if some documentation says this:

"foo() is available in foo.h, and bar() is available in bar.h".

Then suppose that foo.h and bar.h both contain this:

#include <foobar.h>

and that foobar.h contains the prototypes for both foo() and bar().

Now let's suppose that your code uses both foo() and bar(), and you,
by trial and error, determine you can get away by only including
foo.h, and you remove the include for bar.h. It will compile OK
right now, but what happens later on when the foobar library that
you're using changes its implementation so that foo()'s prototype
is really in foo.h and bar()'s prototype is really in bar.h? You
will have created for yourself a horrible mess because your #includes
are depending on quirks of the .h files which aren't guaranteed
rather than depending on what is guaranteed by the documentation.

More to the point, how can any automated program that just looks
at header files tell which header files are the ones that the
documentation guarantees will work?

I suppose it might be possible in some limited cases to write such
a tool, such as if no .h file every includes another .h file, but
that's not how most .h files usually work...

- Logan

**Steven Woody** · Jan 14 '06, 08:45 AM

Re: detect necessary #includes

Logan Shaw wrote:[color=blue]
> Steven Woody wrote:[color=green]
> > hi,
> >
> > after some weeks of development of a project, there likely are many
> > "#include" in source files which was added before but are now
> > unnecessary. is there any tool which can find out those "#include"s
> > and tell me it's safe to remove them? manual work is so time consuming.[/color]
>
> Only a standards document or other API documentation can really tell
> you whether it's safe to remove a #include.
>
> Consider what happens if some documentation says this:
>
> "foo() is available in foo.h, and bar() is available in bar.h".
>
> Then suppose that foo.h and bar.h both contain this:
>
> #include <foobar.h>
>
> and that foobar.h contains the prototypes for both foo() and bar().
>
> Now let's suppose that your code uses both foo() and bar(), and you,
> by trial and error, determine you can get away by only including
> foo.h, and you remove the include for bar.h. It will compile OK
> right now, but what happens later on when the foobar library that
> you're using changes its implementation so that foo()'s prototype
> is really in foo.h and bar()'s prototype is really in bar.h? You
> will have created for yourself a horrible mess because your #includes
> are depending on quirks of the .h files which aren't guaranteed
> rather than depending on what is guaranteed by the documentation.
>
> More to the point, how can any automated program that just looks
> at header files tell which header files are the ones that the
> documentation guarantees will work?
>
> I suppose it might be possible in some limited cases to write such
> a tool, such as if no .h file every includes another .h file, but
> that's not how most .h files usually work...
>
> - Logan[/color]

i am not going to remove any standard or system wide #includes, i am
going to remove those #includes which include my own headers.

**Bjørn Augestad** · Jan 14 '06, 09:05 AM

Re: detect necessary #includes

Steven Woody wrote:[color=blue]
> hi,
>
> after some weeks of development of a project, there likely are many
> "#include" in source files which was added before but are now
> unnecessary. is there any tool which can find out those "#include"s
> and tell me it's safe to remove them? manual work is so time consuming.
> thanks.
>
> -
> woody
>[/color]

PC-lint(www.gimpel.com) does that, IIRC.
Bjørn

**Richard Heathfield** · Jan 14 '06, 09:25 AM

Re: detect necessary #includes

Steven Woody said:
[color=blue]
> hi,
>
> after some weeks of development of a project, there likely are many
> "#include" in source files which was added before but are now
> unnecessary. is there any tool which can find out those "#include"s
> and tell me it's safe to remove them? manual work is so time consuming.
> thanks.[/color]

Remove all your headers, and recompile. Then see what the compiler moans
about. This may also help you to refactor your headers in a more sensible
way.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

**Mark McIntyre** · Jan 14 '06, 11:38 AM

Re: detect necessary #includes

On 13 Jan 2006 23:47:03 -0800, in comp.lang.c , "Steven Woody"
<narkewoody@gma il.com> wrote:
[color=blue]
>hi,
>
>after some weeks of development of a project, there likely are many
>"#include" in source files which was added before but are now
>unnecessary. is there any tool which can find out those "#include"s
>and tell me it's safe to remove them? manual work is so time consuming.[/color]

Well, you could us an cross-ref tool to build up a list of which
functions are used and which #include they come from, then by process
of elimination work out which ones you don't need. If you have a many
MLOC legacy project split into dozens of libs, thats how I'd do it.

However for a project you've been working on for only weeks, it would
be quicker to just comment out any header you don't think you need,
recompile and watch the warnings.
Mark McIntyre
--

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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**Steven Woody** · Jan 14 '06, 12:05 PM

Re: detect necessary #includes

Richard Heathfield wrote:[color=blue]
> Steven Woody said:
>[color=green]
> > hi,
> >
> > after some weeks of development of a project, there likely are many
> > "#include" in source files which was added before but are now
> > unnecessary. is there any tool which can find out those "#include"s
> > and tell me it's safe to remove them? manual work is so time consuming.
> > thanks.[/color]
>
> Remove all your headers, and recompile. Then see what the compiler moans
> about. This may also help you to refactor your headers in a more sensible
> way.
>[/color]

thanks for all your advices. commenting out all headers then add one by
one seems the only solution i can adapt thought i wish there exists a
more time saving method. pc-lint is not suite to me since i am working
on Linux. thanks again.

**Emmanuel Delahaye** · Jan 14 '06, 12:05 PM

Re: detect necessary #includes

Steven Woody a écrit :[color=blue]
> after some weeks of development of a project, there likely are many
> "#include" in source files which was added before but are now
> unnecessary.[/color]

Who knows ? Things can change and the guards are doing their job. Don't
touch anything. You'll gain peanuts.

--
A+

Emmanuel Delahaye

**Richard Heathfield** · Jan 14 '06, 01:55 PM

Re: detect necessary #includes

Steven Woody said:
[color=blue]
> thanks for all your advices. commenting out all headers[/color]

Please, please, please don't do this. If you want to rip them out
temporarily, do it like so:

#if 0
#include "foo.h"
#include "bar.h"
#include "baz.h"
#include "quux.h"
#endif

Then, as you discover you need them, fish them out of the #if and into the
code proper.

Comment syntax is for adding something extra to the code, not for taking
something away.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

**Steven Woody** · Jan 14 '06, 03:35 PM

Re: detect necessary #includes

Richard Heathfield wrote:[color=blue]
> Steven Woody said:
>[color=green]
> > thanks for all your advices. commenting out all headers[/color]
>
> Please, please, please don't do this. If you want to rip them out
> temporarily, do it like so:
>
> #if 0
> #include "foo.h"
> #include "bar.h"
> #include "baz.h"
> #include "quux.h"
> #endif[/color]

i've not seen big difference between this method and that of commting.
[color=blue]
>
> Then, as you discover you need them, fish them out of the #if and into the
> code proper.
>
> Comment syntax is for adding something extra to the code, not for taking
> something away.[/color]

how to understand this ? i am so interesting

**Emmanuel Delahaye** · Jan 14 '06, 05:05 PM

Re: detect necessary #includes

Richard Heathfield a écrit :[color=blue]
> #if 0
> #include "foo.h"
> #include "bar.h"
> #include "baz.h"
> #include "quux.h"
> #endif
>
> Then, as you discover you need them, fish them out of the #if and into the
> code proper.[/color]

"fish them out"

I like it !

--
A+

Emmanuel Delahaye

**Richard Heathfield** · Jan 14 '06, 05:15 PM

Re: detect necessary #includes

Steven Woody said:
[color=blue]
>
> Richard Heathfield wrote:[color=green]
>> Steven Woody said:
>>[color=darkred]
>> > thanks for all your advices. commenting out all headers[/color]
>>
>> Please, please, please don't do this. If you want to rip them out
>> temporarily, do it like so:
>>
>> #if 0
>> #include "foo.h"
>> #include "bar.h"
>> #include "baz.h"
>> #include "quux.h"
>> #endif[/color]
>
> i've not seen big difference between this method and that of commting.[/color]

The obvious difference is that "commenting out" code is an abuse of the
syntax. But perhaps you're not so interested in clarity, and want a more
practical motivation. Okay, here it is:

foo(); /* do the foo thing */
if(condition) /* we only want to bar if there's an 'r' in the month */
{
bar(); /* this will use the default directory, C:\bar\ */
baz(); /* don't forget to baz everything back to normal */
}

Observe the problem with "commenting out" this code:

/*
foo(); /* do the foo thing */
if(condition) /* we only want to bar if there's an 'r' in the month */
{
bar(); /* this will use the default directory, C:\bar\ */
baz(); /* don't forget to baz everything back to normal */
}
*/

See the difficulty? Only the foo() call has been "commented out". And now
you have a syntax error on the last line - "unmatched closing comment" or
similar.

Now let's do it properly:

#if 0
foo(); /* do the foo thing */
if(condition) /* we only want to bar if there's an 'r' in the month */
{
bar(); /* this will use the default directory, C:\bar\ */
baz(); /* don't forget to baz everything back to normal */
}
#endif

No syntax error. No problem with existing comments. And to undo it, you need
only change a single character (change 0 to 1) - and of course it's just as
easy to re-do it.
[color=blue][color=green]
>> Then, as you discover you need them, fish them out of the #if and into
>> the code proper.
>>
>> Comment syntax is for adding something extra to the code, not for taking
>> something away.[/color]
>
> how to understand this ? i am so interesting[/color]

Unmatched closing comment.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

**Keith Thompson** · Jan 14 '06, 07:45 PM

Re: detect necessary #includes

Mark McIntyre <markmcintyre@s pamcop.net> writes:[color=blue]
> On 13 Jan 2006 23:47:03 -0800, in comp.lang.c , "Steven Woody"
> <narkewoody@gma il.com> wrote:[color=green]
>>after some weeks of development of a project, there likely are many
>>"#include" in source files which was added before but are now
>>unnecessary . is there any tool which can find out those "#include"s
>>and tell me it's safe to remove them? manual work is so time consuming.[/color]
>
> Well, you could us an cross-ref tool to build up a list of which
> functions are used and which #include they come from, then by process
> of elimination work out which ones you don't need. If you have a many
> MLOC legacy project split into dozens of libs, thats how I'd do it.[/color]

The cross-ref tool would only tell you about headers that provide
function declarations.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

**Keith Thompson** · Jan 14 '06, 07:55 PM

Re: detect necessary #includes

Richard Heathfield <invalid@invali d.invalid> writes:[color=blue]
> Steven Woody said:[color=green]
>> thanks for all your advices. commenting out all headers[/color]
>
> Please, please, please don't do this. If you want to rip them out
> temporarily, do it like so:
>
> #if 0
> #include "foo.h"
> #include "bar.h"
> #include "baz.h"
> #include "quux.h"
> #endif
>
> Then, as you discover you need them, fish them out of the #if and into the
> code proper.
>
> Comment syntax is for adding something extra to the code, not for taking
> something away.[/color]

Uncomfortable as it is to disagree with Richard, I have to say I don't
think this is a big deal. Commenting out substantial blocks of code
is a bad idea, partly because comments don't nest, but I don't see a
problem with commenting out #include directives one at a time:

/* #include "foo.h" */
/* #include "bar.h" */
/* #include "baz.h" */
/* #include "quux.h" */

With the "#if 0", re-adding "bar.h" results in:

#if 0
#include "foo.h"
#endif
#include "bar.h"
#if 0
#include "baz.h"
#include "quux.h"
#endif

as opposed to:

/* #include "foo.h" */
#include "bar.h"
/* #include "baz.h" */
/* #include "quux.h" */

which makes it much easier to tell at a glance which lines are active
and which ones aren't.

Furthermore, the whole idea any #includes that are commented out will
eventually be removed altogether, so the comments are only temporary.

There is a risk if you have comments on the #include lines, but then
you just have to be careful to comment out only the directive, not the
entire line.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

**Richard Heathfield** · Jan 14 '06, 09:35 PM

Re: detect necessary #includes

Keith Thompson said:
[color=blue]
> Uncomfortable as it is to disagree with Richard,[/color]

That should tell you something right there. :-)
[color=blue]
> I have to say I don't
> think this is a big deal. Commenting out substantial blocks of code
> is a bad idea, partly because comments don't nest, but I don't see a
> problem with commenting out #include directives one at a time:
>
> /* #include "foo.h" */
> /* #include "bar.h" */
> /* #include "baz.h" */
> /* #include "quux.h" */
>
> With the "#if 0", re-adding "bar.h" results in:
>
> #if 0
> #include "foo.h"
> #endif
> #include "bar.h"
> #if 0
> #include "baz.h"
> #include "quux.h"
> #endif[/color]

Huh? What are you talking about?

Before:

#if 0
#include "foo.h"
#include "bar.h"
#include "baz.h"
#include "quux.h"
#endif

Edit:

/bar
dd2jp

After:

#if 0
#include "foo.h"
#include "baz.h"
#include "quux.h"
#endif
#include "bar.h"

The quickest way I can find to remove the comments you used is:

/bar
03x$2Xx

which is actually slightly more work.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)