precompiled headers

precompiled headers

[Adrian Sandor]

Hello

I am using gcc 3.2 (included in dev-c++ 4.9.7.0 with
mingw), and I'd like to know how I can generate and
use precompiled headers in my programs, because
without them it takes ages to compile my programs.

regards,
 Adrian

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Re: precompiled headers

[John Love-Jensen]

Hello Adrian,

I may be mistaken, but I don't think there are precompiled headers in GCC
3.2.

However, I'm surprised that it's taking so long.  I work with some massively
large projects, and the compiles don't take an egregious amount of time.
(On a 400MHz SPARC.)

Do your source files (.cpp and .h) include only the headers they need, or
are they including the world?

If they're including the world, I strongly suggest your project team
discipline themselves to only include things that are directly needed by
that source file.  And NEVER rely on incidental inclusion of a needed header
file merely because some other included header file happens to include it.

--Eljay

Re: precompiled headers

[Diego Novillo]

In article <20030121125259.29702.qmail@web40309.mail.yahoo.com>, Adrian Sandor wrote:

> I am using gcc 3.2 (included in dev-c++ 4.9.7.0 with
> mingw), and I'd like to know how I can generate and
> use precompiled headers in my programs, because
> without them it takes ages to compile my programs.
> 
No.  Precompiled headers will be available with gcc 3.4.


Diego.

Re: precompiled headers

[Adrian Sandor]

thank you for your reply 

--- John Love-Jensen wrote:
> I may be mistaken, but I don't think there are
> precompiled headers in GCC
> 3.2.

then which version supports precompiled headers? do I
need to get 3.2.1?

> However, I'm surprised that it's taking so long.
> Do your source files (.cpp and .h) include only the
> headers they need, or
> are they including the world?

I am using a slow computer, and my files are including
a few stl headers and a few headers written by me; a
very small program takes about 40 seconds to compile,
and I need to recompile often, that's why I want to
use precompiled headers

thanks,
 Adrian


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Re: precompiled headers

[Alexander Helm]

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Hash: SHA1

I've searched for something like this some time ago. A good solution (at
least for me) was ccache (http://ccache.samba.org/). It's not perfect
but it is a step in the right direction (and it's safe as far as the
webpage and my experiences are concerned.

	HTH
	Alexander

Adrian Sandor wrote:
| thank you for your reply
|
| --- John Love-Jensen wrote:
|
|>I may be mistaken, but I don't think there are
|>precompiled headers in GCC
|>3.2.
|
|
| then which version supports precompiled headers? do I
| need to get 3.2.1?
|
|
|>However, I'm surprised that it's taking so long.
|>Do your source files (.cpp and .h) include only the
|>headers they need, or
|>are they including the world?
|
|
| I am using a slow computer, and my files are including
| a few stl headers and a few headers written by me; a
| very small program takes about 40 seconds to compile,
| and I need to recompile often, that's why I want to
| use precompiled headers
|
| thanks,
|  Adrian
|
|
| __________________________________________________
| Do you Yahoo!?
| Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
| http://mailplus.yahoo.com

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Re: precompiled headers

[Per Rosengren]

The compiler flags given when compiling a source file that uses a 
precompiled header must match those used when the precompiled header was 
compiled. Because of this I altered Brian's code to:

BUILT_SOURCES = myheader.hh.gch
%.hh.gch: %.hh
	$(CXXCOMPILE) -c $<

The only difference here is that CXXCOMPILE - which is used to compile 
my sources, adds some flags to CXX.
For debugging purposes, I added

AM_CXXFLAGS = -H -Winvalid-pch

where -H prints all header files included, and -Winvalid-pch warns if a 
precompiled header was found but not used.

I think all dependencies are correct.


Thank you!
Per

Ralf Wildenhues wrote:
> * Brian Dessent wrote on Fri, Apr 18, 2008 at 11:28:07AM CEST:
>> BUILT_SOURCES = myheader.hh.gch
>> %.hh.gch: %.hh
>> 	$(CXX) -c $<
> [...] 
> 
> The rule is a good start, but likely lacking dependency information.
> 
>> But honestly the above is just a random stab at how to start, you'd be
>> much better asking on the automake list (in CC:.)
> 
> My humble musings about precompiled headers support are mostly in
> <http://thread.gmane.org/gmane.comp.gcc.devel/60371>, and those
> affect GCC-type precompiled headers only.
> 
> Cheers,
> Ralf

Re: precompiled headers

[Ralf Wildenhues]

* Brian Dessent wrote on Fri, Apr 18, 2008 at 11:28:07AM CEST:
> BUILT_SOURCES = myheader.hh.gch
> %.hh.gch: %.hh
> 	$(CXX) -c $<
[...] 

The rule is a good start, but likely lacking dependency information.

> But honestly the above is just a random stab at how to start, you'd be
> much better asking on the automake list (in CC:.)

My humble musings about precompiled headers support are mostly in
<http://thread.gmane.org/gmane.comp.gcc.devel/60371>, and those
affect GCC-type precompiled headers only.

Cheers,
Ralf

Re: precompiled headers

[Ian Lance Taylor]

"Yannick Beynet" <beynet@fresnes.info> writes:

> I try to use precompiled headers with gcc 3.4.0
> It's working but I notice that sometimes they are not used.
> for example in a cpp file witch starts like :
> #include "h1.H"
> #include "h2.H"
> 
> h1.H.gch is used, but most of time h2.H.gch is not used. I guess it is
> because h1.H includes some files witch are not also precompiled. Am I
> right ?

Only one precompiled header is used per compilation.  See the
documentation.

Ian

precompiled headers

[Yannick Beynet]

HI !
I try to use precompiled headers with gcc 3.4.0
It's working but I notice that sometimes they are not used.
for example in a cpp file witch starts like :
#include "h1.H"
#include "h2.H"

h1.H.gch is used, but most of time h2.H.gch is not used. I guess it is
because h1.H includes some files witch are not also precompiled. Am I
right ?

Thanks.

PS : do you have a solution to force using both h1.H.gch and h1.H.gch