how to do two-stage preprocessing of one file

[andreyvul]

What I'm trying to do is have the preprocessor parse one file twice.
The file has three parts, and each is dependent on the previous.
Example (file name is foo.c):
#ifndef ONCE /* first part */
#define D #define
#define ONCE
#include "foo.c"
#endif
#ifdef ONCE /* second part */
D x int
#ifndef TWICE
#define TWICE
#include "foo.c"
#endif
#endif
#ifdef TWICE /* third part */
x y;
#endif

The problem is that the preprocessor just adds the third part to the
second part, but doesn't preprocess the third part in the process.
How do I make my #includes and #ifedefs so that the third part will be
preprocessed?

[Walter Roberson]

In article <11************ *********@k79g2 000hse.googlegr oups.com>,
andreyvul <an********@gma il.comwrote:

>What I'm trying to do is have the preprocessor parse one file twice.

You cannot do that using the facilities defined by the C preprocessor.

Your particular implementation -probably- offers a way to
preprocess files. For example, on the system I am using at the
moment, the sequence would look something like,

cc -P myfile.c
mv myfile.i myfile_preproce ssed.c
cc -o outputfile myfile_preproce ssed.c

But it would also not be uncommon on a Unix system for the sequence
to look something closer to

cc -E myfile.c | egrep -v '^#line' myfile_preproce ssed.c
cc -o outfile myfile_preproce ssed.c

Many unix C compilers offer some option as in the second example,
to preprocess and send the result to standard output; it may
or may not be necessary in your toolchain to remove #line directives
from the preprocessed output before you can push the file back
through the C parseer.

If you are using one of the Windows compilers... there is probably
some similar option, but probably not named -P or -E .
--
"Is there any thing whereof it may be said, See, this is new? It hath
been already of old time, which was before us." -- Ecclesiastes

[andreyvul]

On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,

andreyvul <andrey....@gma il.comwrote:

What I'm trying to do is have the preprocessor parse one file twice.

You cannot do that using the facilities defined by the C preprocessor.

Oh, I meant _recursively_ preprocess the file twice.
That's why I was asking about proper #include/#ifdef structure, so
that it preprocesses like this:

#block 1
|->#block 2 (via recursive include)
|->#block 3 (via recursive include)

however, it doesn't get to |->#block 3

[Ark Khasin]

andreyvul wrote:

On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

>In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,

andreyvul <andrey....@gma il.comwrote:

>>What I'm trying to do is have the preprocessor parse one file twice.

You cannot do that using the facilities defined by the C preprocessor.

Oh, I meant _recursively_ preprocess the file twice.
That's why I was asking about proper #include/#ifdef structure, so
that it preprocesses like this:

#block 1
|->#block 2 (via recursive include)
|->#block 3 (via recursive include)

however, it doesn't get to |->#block 3

I didn't try it but something along these lines might do it:

#ifndef REC_COUNT
#define REC_COUNT 2
#elif REC_COUNT == 2
#undef REC_COUNT
#define REC_COUNT 1
#elif REC_COUNT == 1
#undef REC_COUNT
#define REC_COUNT 0
#endif
/* Here is the meat */
#if REC_COUNT == 2
/* first iteration */
#elif REC_COUNT == 1
/* second iteration */
#else
/* third and last iteration */
#if REC_COUNT != 0
#include __FILE__
#endif

--
Ark

[Walter Roberson]

In article <11************ **********@d55g 2000hsg.googleg roups.com>,
andreyvul <an********@gma il.comwrote:

>On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

>In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,

>andreyvul <andrey....@gma il.comwrote:

>What I'm trying to do is have the preprocessor parse one file twice.

>You cannot do that using the facilities defined by the C preprocessor.

>Oh, I meant _recursively_ preprocess the file twice.

Oh, in that case, let me correct my statement:

The facilities of the C preprocessor are defined in such a way that
you are not guaranteed to be able to do this; if you were able to
get it to work at all, it would be due to implementation-dependant
behaviour.
--
"History is a pile of debris" -- Laurie Anderson

[andreyvul]

On Nov 12, 7:58 pm, Ark Khasin <akha...@macroe xpressions.comw rote:

andreyvul wrote:

On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,

andreyvul <andrey....@gma il.comwrote:
What I'm trying to do is have the preprocessor parse one file twice.
You cannot do that using the facilities defined by the C preprocessor.

Oh, I meant _recursively_ preprocess the file twice.
That's why I was asking about proper #include/#ifdef structure, so
that it preprocesses like this:

#block 1
|->#block 2 (via recursive include)
|->#block 3 (via recursive include)

however, it doesn't get to |->#block 3

I didn't try it but something along these lines might do it:

#ifndef REC_COUNT
#define REC_COUNT 2
#elif REC_COUNT == 2
#undef REC_COUNT
#define REC_COUNT 1
#elif REC_COUNT == 1
#undef REC_COUNT
#define REC_COUNT 0
#endif
/* Here is the meat */
#if REC_COUNT == 2
/* first iteration */
#elif REC_COUNT == 1
/* second iteration */
#else
/* third and last iteration */
#if REC_COUNT != 0
#include __FILE__
#endif

--
Ark

Nope, doesn't work.

Great, I have now figured out it is impossible to recursively
preprocess more than one level. Is this supposed to happen per ANSI
specs, or should I go to the cpp newsgroup?

[andreyvul]

And I got it to work now:
cc foo.c -E | sed -re '/#[^di]/D' -e /^$/D' | head -7 | cc -x c - -o
foo
Kind of impossible on windows without GnuWin32, msys, or cygwin.

[Ark Khasin]

andreyvul wrote:

On Nov 12, 7:58 pm, Ark Khasin <akha...@macroe xpressions.comw rote:

>andreyvul wrote:

>>On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:
In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,
andreyvul <andrey....@gma il.comwrote:
What I'm trying to do is have the preprocessor parse one file twice.
You cannot do that using the facilities defined by the C preprocessor.
Oh, I meant _recursively_ preprocess the file twice.
That's why I was asking about proper #include/#ifdef structure, so
that it preprocesses like this:
#block 1
|->#block 2 (via recursive include)
|->#block 3 (via recursive include)
however, it doesn't get to |->#block 3

I didn't try it but something along these lines might do it:

#ifndef REC_COUNT
#define REC_COUNT 2
#elif REC_COUNT == 2
#undef REC_COUNT
#define REC_COUNT 1
#elif REC_COUNT == 1
#undef REC_COUNT
#define REC_COUNT 0
#endif
/* Here is the meat */
#if REC_COUNT == 2
/* first iteration */
#elif REC_COUNT == 1
/* second iteration */
#else
/* third and last iteration */
#if REC_COUNT != 0
#include __FILE__
#endif

--
Ark

Nope, doesn't work.

Great, I have now figured out it is impossible to recursively
preprocess more than one level. Is this supposed to happen per ANSI
specs, or should I go to the cpp newsgroup?

You didn't try hard enough :). The text I posted was not #balanced.
Here's a working example:
------------- iter.c -------------
#include <stdio.h>
int main()
{
#include "iter.h"
return 0;
}
------------- iter.h -------------
#ifndef REC_COUNT
# define REC_COUNT 2
/* first iteration */
puts("first iteration");
#elif REC_COUNT == 2
# undef REC_COUNT
# define REC_COUNT 1
/* second iteration */
puts("second iteration");
#elif REC_COUNT == 1
# undef REC_COUNT
# define REC_COUNT 0
/* third and last iteration */
puts("third and last iteration");
#endif
#if REC_COUNT != 0
# include __FILE__
#endif
------------ output --------------------
first iteration
second iteration
third and last iteration

.... which also disproves a claim of a nearby post that it's impossible.
In fact, you can do recursion of any fixed depth this way.
Unless of course I misunderstood what you were trying to achieve.

--
Ark

[andreyvul]

On Nov 12, 9:54 pm, Ark Khasin <akha...@macroe xpressions.comw rote:

andreyvul wrote:

On Nov 12, 7:58 pm, Ark Khasin <akha...@macroe xpressions.comw rote:

andreyvul wrote:
On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:
In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,
andreyvul <andrey....@gma il.comwrote:
What I'm trying to do is have the preprocessor parse one file twice.
You cannot do that using the facilities defined by the C preprocessor.
Oh, I meant _recursively_ preprocess the file twice.
That's why I was asking about proper #include/#ifdef structure, so
that it preprocesses like this:
#block 1
|->#block 2 (via recursive include)
|->#block 3 (via recursive include)
however, it doesn't get to |->#block 3
I didn't try it but something along these lines might do it:

#ifndef REC_COUNT
#define REC_COUNT 2
#elif REC_COUNT == 2
#undef REC_COUNT
#define REC_COUNT 1
#elif REC_COUNT == 1
#undef REC_COUNT
#define REC_COUNT 0
#endif
/* Here is the meat */
#if REC_COUNT == 2
/* first iteration */
#elif REC_COUNT == 1
/* second iteration */
#else
/* third and last iteration */
#if REC_COUNT != 0
#include __FILE__
#endif

--
Ark

Nope, doesn't work.

Great, I have now figured out it is impossible to recursively
preprocess more than one level. Is this supposed to happen per ANSI
specs, or should I go to the cpp newsgroup?

You didn't try hard enough :). The text I posted was not #balanced.
Here's a working example:
------------- iter.c -------------
#include <stdio.h>
int main()
{
#include "iter.h"
return 0;}

------------- iter.h -------------
#ifndef REC_COUNT
# define REC_COUNT 2
/* first iteration */
puts("first iteration");
#elif REC_COUNT == 2
# undef REC_COUNT
# define REC_COUNT 1
/* second iteration */
puts("second iteration");
#elif REC_COUNT == 1
# undef REC_COUNT
# define REC_COUNT 0
/* third and last iteration */
puts("third and last iteration");
#endif
#if REC_COUNT != 0
# include __FILE__
#endif
------------ output --------------------
first iteration
second iteration
third and last iteration

... which also disproves a claim of a nearby post that it's impossible.
In fact, you can do recursion of any fixed depth this way.
Unless of course I misunderstood what you were trying to achieve.

--
Ark

What if you had a macro in the third iteration that was to be expanded
by the previous iterations?

[andreyvul]

On Nov 12, 9:54 pm, Ark Khasin <akha...@macroe xpressions.comw rote:

andreyvul wrote:

On Nov 12, 7:58 pm, Ark Khasin <akha...@macroe xpressions.comw rote:

andreyvul wrote:
On Nov 12, 7:11 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:
In article <1194910305.752 743.81...@k79g2 000hse.googlegr oups.com>,
andreyvul <andrey....@gma il.comwrote:
What I'm trying to do is have the preprocessor parse one file twice.
You cannot do that using the facilities defined by the C preprocessor.
Oh, I meant _recursively_ preprocess the file twice.
That's why I was asking about proper #include/#ifdef structure, so
that it preprocesses like this:
#block 1
|->#block 2 (via recursive include)
|->#block 3 (via recursive include)
however, it doesn't get to |->#block 3
I didn't try it but something along these lines might do it:

#ifndef REC_COUNT
#define REC_COUNT 2
#elif REC_COUNT == 2
#undef REC_COUNT
#define REC_COUNT 1
#elif REC_COUNT == 1
#undef REC_COUNT
#define REC_COUNT 0
#endif
/* Here is the meat */
#if REC_COUNT == 2
/* first iteration */
#elif REC_COUNT == 1
/* second iteration */
#else
/* third and last iteration */
#if REC_COUNT != 0
#include __FILE__
#endif

--
Ark

Nope, doesn't work.

Great, I have now figured out it is impossible to recursively
preprocess more than one level. Is this supposed to happen per ANSI
specs, or should I go to the cpp newsgroup?

You didn't try hard enough :). The text I posted was not #balanced.
Here's a working example:
------------- iter.c -------------
#include <stdio.h>
int main()
{
#include "iter.h"
return 0;}

------------- iter.h -------------
#ifndef REC_COUNT
# define REC_COUNT 2
/* first iteration */
puts("first iteration");
#elif REC_COUNT == 2
# undef REC_COUNT
# define REC_COUNT 1
/* second iteration */
puts("second iteration");
#elif REC_COUNT == 1
# undef REC_COUNT
# define REC_COUNT 0
/* third and last iteration */
puts("third and last iteration");
#endif
#if REC_COUNT != 0
# include __FILE__
#endif
------------ output --------------------
first iteration
second iteration
third and last iteration

... which also disproves a claim of a nearby post that it's impossible.
In fact, you can do recursion of any fixed depth this way.
Unless of course I misunderstood what you were trying to achieve.

--
Ark

What if you have a macro in the third iteration that needs expanding
in the second iteration, which needs expanding in the first iteration?
*That* was what I was trying to do.