Thread: Avoid double compile

I'm using stxxl library, and recently I noticed that compile time is significantly increased. Therefore, I tried to make use of precompiled header files.
This is the content of "precompiled.h"

Code:

#include <iostream>
 
#include <stxxl/vector>
#include <stxxl/priority_queue>
#include <stxxl/sort>
#include <stxxl/scan>
#include <stxxl/stream>

#include <string> 
#include <sstream>
#include <cstdlib>
#include <ctime>
#include <cmath>  
#include <vector>   
#include <limits.h>
#include <queue>
#include <algorithm>
#include <numeric>
#include <typeinfo>
#include <fstream>              
#include <cairo.h>
#include <cairo-pdf.h>
#include <myFile1.cpp>
#include <myFile2.cpp>

and the content of a specific corresponding makefile is

Code:

STXXL_ROOT      ?= /home/mirza/stxxl-1.2.1
STXXL_CONFIG    ?= stxxl.mk
include $(STXXL_ROOT)/$(STXXL_CONFIG)

# use the variables from stxxl.mk

CXX              = $(STXXL_CXX)
CPPFLAGS        += $(STXXL_CPPFLAGS)

# add your own optimization, warning, debug, ... flags
# (these are *not* set in stxxl.mk)
CPPFLAGS        += $(shell pkg-config --cflags cairo)
STXXL_LDLIBS    += $(shell pkg-config --libs cairo)

CPPFLAGS        += -O3 -Wall -g -c -DFOO=BAR

# build your application
# (my_example.o is generated from my_example.cpp automatically)

precompiled.o: precompiled.h
	$(CXX) $(CPPFLAGS) $(CXXFLAGS) precompiled.h -o $@ $(STXXL_LDLIBS)

The first line of the .cpp file is "include "precompiled.h", but after invoking makefile specific for that .cpp file, I get reports and warnings that I got when invoking makefile specific for header file. So, it seems that it compiles again. I've read that the precompiled header files produce .gch files that are automatically sought to be incorporated. In my header specific makefile I could not "tell the compiler" I want .gch as output to be later used by main .cpp file. It only accepts .o.
Any thoughts on how to do this properly?
Thanks
To, maybe, make things easier, I include the content of the makefile specific for the fileA.cpp, which is main file, and contains "include "precompiled.h"" line

Code:

STXXL_ROOT      ?= /home/mirza/stxxl-1.2.1
STXXL_CONFIG    ?= stxxl.mk
include $(STXXL_ROOT)/$(STXXL_CONFIG)

# use the variables from stxxl.mk

CXX              = $(STXXL_CXX)
CPPFLAGS        += $(STXXL_CPPFLAGS)

# add your own optimization, warning, debug, ... flags
# (these are *not* set in stxxl.mk)

CPPFLAGS        += $(shell pkg-config --cflags cairo)
STXXL_LDLIBS    += $(shell pkg-config --libs cairo)


CPPFLAGS        += -O3 -Wall -g -DFOO=BAR

# build your application
# (my_example.o is generated from my_example.cpp automatically)
fileA.bin: fileA.o
    $(CXX) $(CPPFLAGS) $(CXXFLAGS) fileA.o -o $@ $(STXXL_LDLIBS)

Maybe changing this file would make things easier? Thanks

First, in the first makefile change:

Code:

precompiled.o: precompiled.h

to:

Code:

precompiled.h.gch: precompiled.h

and in the 2nd makefile change:

Code:

CPPFLAGS        += -O3 -Wall -g -DFOO=BAR

to:

Code:

CPPFLAGS        += -O3 -Wall -g -DFOO=BAR -include precompiled.h

Next, why are you #including .cpp files?

I went through this same problem just a few days ago.
I assume you read this page: Precompiled Headers - Using the GNU Compiler Collection (GCC)
Are you sure the .gch file and the rest of your .o files are being compiled with exactly the same compiler flags...?

Try adding a -H flag to both of them and then you can see exactly which header files are being included for each file. If the .gch file is being used by g++ it will print a ! at the beginning of the line; if it's not used, it'll print an X instead.

Originally Posted by onako

cpp files are included in other cpp files (or h files), inherited project.

Don't do that. Compile .cpp files; don't include them.

Originally Posted by Elysia

Don't do that. Compile .cpp files; don't include them.

Did you miss the part about "inherited project?"

There are a couple of legitimate reasons that might be done, though most people won't ever run into that.

I didn't miss it, but perhaps I missed the point about why it was as it is.