tree.h vs include guard

tree.h vs include guard

[Gabriel Dos Reis]

Hi,

  I noticed that tree.h has no guard to prevent multiple-inclusions.
Why so?  FWIW, c-tree.h, c-common.h and cp-tree.h do have such a
thing.

-- Gaby

Re: tree.h vs include guard

[Devang Patel]

We already have guard in our Darwin sources for tree.h

I do not know, if there is particular reason for not providing guards 
for headers.
At one time, I saw many headers without include protection guards.

On Tuesday, August 13, 2002, at 05:54  PM, Gabriel Dos Reis wrote:

Hi,

  I noticed that tree.h has no guard to prevent multiple-inclusions.
Why so?  FWIW, c-tree.h, c-common.h and cp-tree.h do have such a
thing.

-- Gaby

Re: tree.h vs include guard

[Zack Weinberg]

On Wed, Aug 14, 2002 at 02:54:29AM +0200, Gabriel Dos Reis wrote:
> 
> Hi,
> 
>   I noticed that tree.h has no guard to prevent multiple-inclusions.
> Why so?  FWIW, c-tree.h, c-common.h and cp-tree.h do have such a
> thing.

Patches to add multiple include guards to all of GCC's internal
headers have been submitted in the past, but never approved and
applied, probably because they'd need an OK from someone with global
write privileges and all those people were too busy to review the
patch.

It was agreed, last time this came up, that in principle they should
all have guards.

zw

Re: tree.h vs include guard

[Gabriel Dos Reis]

Zack Weinberg <zack@codesourcery.com> writes:

| On Wed, Aug 14, 2002 at 02:54:29AM +0200, Gabriel Dos Reis wrote:
| > 
| > Hi,
| > 
| >   I noticed that tree.h has no guard to prevent multiple-inclusions.
| > Why so?  FWIW, c-tree.h, c-common.h and cp-tree.h do have such a
| > thing.
| 
| Patches to add multiple include guards to all of GCC's internal
| headers have been submitted in the past, but never approved and
| applied, probably because they'd need an OK from someone with global
| write privileges and all those people were too busy to review the
| patch.
| 
| It was agreed, last time this came up, that in principle they should
| all have guards.

Thanks for the reminder.  Do you have references to those patches?
I realized that we're in stage 3, so maybe those patches are
inappropriate at this moment; but I think they should be queued for
after mainline is unfrozen.

-- Gaby

Re: tree.h vs include guard

[Zack Weinberg]

On Mon, Aug 26, 2002 at 11:17:33AM +0200, Gabriel Dos Reis wrote:
> Zack Weinberg <zack@codesourcery.com> writes:
> 
> | On Wed, Aug 14, 2002 at 02:54:29AM +0200, Gabriel Dos Reis wrote:
> | > 
> | > Hi,
> | > 
> | >   I noticed that tree.h has no guard to prevent multiple-inclusions.
> | > Why so?  FWIW, c-tree.h, c-common.h and cp-tree.h do have such a
> | > thing.
> | 
> | Patches to add multiple include guards to all of GCC's internal
> | headers have been submitted in the past, but never approved and
> | applied, probably because they'd need an OK from someone with global
> | write privileges and all those people were too busy to review the
> | patch.
> | 
> | It was agreed, last time this came up, that in principle they should
> | all have guards.
> 
> Thanks for the reminder.  Do you have references to those patches?
> I realized that we're in stage 3, so maybe those patches are
> inappropriate at this moment; but I think they should be queued for
> after mainline is unfrozen.

http://gcc.gnu.org/ml/gcc-patches/2001-02/msg01342.html and followups.
This is something that could go on the gcc-3_4-basic-improvements-branch,
if we could get review for it.  The patches need updating.

zw

Re: tree.h vs include guard

[Richard Henderson]

On Thu, Aug 29, 2002 at 04:48:02PM -0700, Zack Weinberg wrote:
> http://gcc.gnu.org/ml/gcc-patches/2001-02/msg01342.html and followups.
> This is something that could go on the gcc-3_4-basic-improvements-branch,
> if we could get review for it.  The patches need updating.

If the quoted patch gets its underscores fixed, it's approved.


r~

Re: tree.h vs include guard

[Neil Booth]

Stan Shebs wrote:-

> I thought the current policy was only to include guards if they were really
> necessary, and for most headers they aren't.  In general GCC policy is to
> explicitly include every header needed by a source file.
> 
> Stan

CPP avoids caching a file if it has include guards, assuming that it's
unlikely it will be relevant again (because of the MI optimization).
So even unnecessary include guards save a bit of memory usage by the compiler.

Neil.

Re: tree.h vs include guard

[Gabriel Dos Reis]

Stan Shebs <shebs@apple.com> writes:

| Devang Patel wrote:
| 
| > We already have guard in our Darwin sources for tree.h
| 
| We have it for a reason - tree.h is included (dubiously IMHO) in one of
| the PFE headers.  I don't see a reason for the mainline to have it though.

Well, I was working on a pretty-printer for C and C++ when I noticed how
painful it was for not having tree.h protect against multiple inclusion.

| 
| >
| > I do not know, if there is particular reason for not providing guards 
| > for headers.
| > At one time, I saw many headers without include protection guards.
| 
| I thought the current policy was only to include guards if they were really
| necessary, and for most headers they aren't.  In general GCC policy is to
| explicitly include every header needed by a source file.

That is what I did for c-pretty-print.[hc] which needed bits from
tree.h. and latter when I included c-pretty-print.h in cp/error.c I
got complaints from the compiler -- realizing minutes later that it
was because tree.h was being included multiple times.  Not having
guard for tree.h means reorganization of the include each time a bits
is added somewhere.  Not a scalable scheme, IMO.
Note that c-tree.h, c-common.h, cp-tree.h already have guards.

-- Gaby

Re: tree.h vs include guard

[Stan Shebs]

Devang Patel wrote: