Re: [cmake-developers] Support for Precompiled Headers
2012/6/14 Daniel Pfeifer dan...@pfeifer-mail.de:
2012/6/14 David Cole david.c...@kitware.com:
Sounds awesome to me!
When can you submit a patch? :-)
Thanks for the motivation! While I would like to contribute a patch, I
have absolutely no idea where to start.
Should it go to cmAddExecutableCommand.cxx and
cmAddLibraryCommand.cxx? Or rather directly to the generator(s)?
Given that the required changes are probably very small (the
implementation that I linked above is less than 100 lines of CMake
code), it is maybe more effort for you to get me started than it is to
implement it... :-)
David,
did you decide whether you want to implement that feature by yourself
or give me an introduction to the CMake architecture?
Where can I find more help? I am a little lost between global and
local generators.
cheers, Daniel
On Thu, Jun 14, 2012 at 4:36 AM, Daniel Pfeifer dan...@pfeifer-mail.de
wrote:
Hi,
In a private mailing with Dave Abrahams and Brad King I wrote a
proposal of how I imagine PCH support should be implemented. Brad
asked me to send it to this list for further discussion.
Please note that even though I use present tense in the proposal,
nothing descibed below is implemented yet.
We have a similar implementation for PCH [1], but the interface
differs to this proposal.
[1]
https://github.com/ryppl/ryppl/blob/develop/cmake/Modules/RypplPrecompileHeader.cmake
cheers, Daniel
CMakeLists.txt changes
--
There are new target properties PRECOMPILE_HEADER and
PRECOMPILE_HEADER_config. These properties may be set to a list of
header files:
set_property(TARGET target APPEND PROPERTY PRECOMPILE_HEADER
boost/spirit/karma.hpp
my/precompiled/header.h
)
changes to source files
---
None. All source files should be written as if there was no PCH
support. That means that each file should include all the headers it
requires. Nothing more, nothing less.
That especially means that source files should *NOT* include an
all.h, precompile.h, or stdafx.h file. Nothing breaks if they
do, but it may impact compile times if precompiled headers are not
supported.
file(s) to precompile
-
Special header files that contain all the system headers may be
created and added to the PRECOMPILE_HEADER property. However, the
system headers may also be added directly to PRECOMPILE_HEADER.
If custom files are created, it is important to note that a special
PCH_SUPPORTED guard is *NOT* required.
What is done behind the scenes
--
CMake creates the actual header file that is going to be precompiled
during the config step inside the current binary directory. The
complete filename encodes the target name and the configuration (eg.
${CMAKE_CURRENT_BINARY_DIR}/${target}_${config}_pch.hpp) and
contains one #include directive for each element in the
PRECOMPILE_HEADER/PRECOMPILE_HEADER_config list. If the element is
wrapped in angle brackets, it is included unmodified, otherwise the
*absolute path* is used in double quotes. The generated header file
for the above example may look like this:
/* generated by CMake 2.8.x */
#include boost/spirit/karma.hpp
#include /home/daniel/workspace/foo/my/precompiled/header.h
This header file is compiled before all object files of the target; ie
the object files depend on the compiled header.
MSVC specific
-
MSVC requires a source file to compile the header. This source file is
generated by CMake alongside the header file and may be called
target_pch.cpp, for example. It contains just one line: an #include
directive that includes the configured header file.
The precompiled header (pch_binary) is created by compiling the source
file (pch_source) with /Yc\${pch_header}\ /Fp\${pch_binary}\.
For the MSVC IDE, pch_binary might be $(IntDir)/${target}.pch.
All other source files are compiled with /Yu\${pch_header}\
/FI\${pch_header}\ /Fp\${pch_binary}\.
/Yc = create pch
/Yu = use pch
/FI = force include
/Fp = name pch binary
GCC specific
In GCC the pch_binary is created by compiling the header file directly
(no extra source file is required). The pch_binary must be
${pch_header}.pch, there is no way to change that. Here, it pays off
again that we generate the actual pch_header in the binary directory.
The compile flags to compile the header are -x c++-header and the
output file must be set with -o ${pch_binary}
All the other source files are compiled with -include ${pch_header}
(force include), it may also be a good idea to pass -Winvalid-pch.
--
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[cmake-developers] Support for Precompiled Headers
Hi,
In a private mailing with Dave Abrahams and Brad King I wrote a
proposal of how I imagine PCH support should be implemented. Brad
asked me to send it to this list for further discussion.
Please note that even though I use present tense in the proposal,
nothing descibed below is implemented yet.
We have a similar implementation for PCH [1], but the interface
differs to this proposal.
[1]
https://github.com/ryppl/ryppl/blob/develop/cmake/Modules/RypplPrecompileHeader.cmake
cheers, Daniel
CMakeLists.txt changes
--
There are new target properties PRECOMPILE_HEADER and
PRECOMPILE_HEADER_config. These properties may be set to a list of
header files:
set_property(TARGET target APPEND PROPERTY PRECOMPILE_HEADER
boost/spirit/karma.hpp
my/precompiled/header.h
)
changes to source files
---
None. All source files should be written as if there was no PCH
support. That means that each file should include all the headers it
requires. Nothing more, nothing less.
That especially means that source files should *NOT* include an
all.h, precompile.h, or stdafx.h file. Nothing breaks if they
do, but it may impact compile times if precompiled headers are not
supported.
file(s) to precompile
-
Special header files that contain all the system headers may be
created and added to the PRECOMPILE_HEADER property. However, the
system headers may also be added directly to PRECOMPILE_HEADER.
If custom files are created, it is important to note that a special
PCH_SUPPORTED guard is *NOT* required.
What is done behind the scenes
--
CMake creates the actual header file that is going to be precompiled
during the config step inside the current binary directory. The
complete filename encodes the target name and the configuration (eg.
${CMAKE_CURRENT_BINARY_DIR}/${target}_${config}_pch.hpp) and
contains one #include directive for each element in the
PRECOMPILE_HEADER/PRECOMPILE_HEADER_config list. If the element is
wrapped in angle brackets, it is included unmodified, otherwise the
*absolute path* is used in double quotes. The generated header file
for the above example may look like this:
/* generated by CMake 2.8.x */
#include boost/spirit/karma.hpp
#include /home/daniel/workspace/foo/my/precompiled/header.h
This header file is compiled before all object files of the target; ie
the object files depend on the compiled header.
MSVC specific
-
MSVC requires a source file to compile the header. This source file is
generated by CMake alongside the header file and may be called
target_pch.cpp, for example. It contains just one line: an #include
directive that includes the configured header file.
The precompiled header (pch_binary) is created by compiling the source
file (pch_source) with /Yc\${pch_header}\ /Fp\${pch_binary}\.
For the MSVC IDE, pch_binary might be $(IntDir)/${target}.pch.
All other source files are compiled with /Yu\${pch_header}\
/FI\${pch_header}\ /Fp\${pch_binary}\.
/Yc = create pch
/Yu = use pch
/FI = force include
/Fp = name pch binary
GCC specific
In GCC the pch_binary is created by compiling the header file directly
(no extra source file is required). The pch_binary must be
${pch_header}.pch, there is no way to change that. Here, it pays off
again that we generate the actual pch_header in the binary directory.
The compile flags to compile the header are -x c++-header and the
output file must be set with -o ${pch_binary}
All the other source files are compiled with -include ${pch_header}
(force include), it may also be a good idea to pass -Winvalid-pch.
--
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Visit other Kitware open-source projects at
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Re: [cmake-developers] Support for Precompiled Headers
2012/6/14 David Cole david.c...@kitware.com:
Sounds awesome to me!
When can you submit a patch? :-)
Thanks for the motivation! While I would like to contribute a patch, I
have absolutely no idea where to start.
Should it go to cmAddExecutableCommand.cxx and
cmAddLibraryCommand.cxx? Or rather directly to the generator(s)?
Given that the required changes are probably very small (the
implementation that I linked above is less than 100 lines of CMake
code), it is maybe more effort for you to get me started than it is to
implement it... :-)
cheers, Daniel
On Thu, Jun 14, 2012 at 4:36 AM, Daniel Pfeifer dan...@pfeifer-mail.de
wrote:
Hi,
In a private mailing with Dave Abrahams and Brad King I wrote a
proposal of how I imagine PCH support should be implemented. Brad
asked me to send it to this list for further discussion.
Please note that even though I use present tense in the proposal,
nothing descibed below is implemented yet.
We have a similar implementation for PCH [1], but the interface
differs to this proposal.
[1]
https://github.com/ryppl/ryppl/blob/develop/cmake/Modules/RypplPrecompileHeader.cmake
cheers, Daniel
CMakeLists.txt changes
--
There are new target properties PRECOMPILE_HEADER and
PRECOMPILE_HEADER_config. These properties may be set to a list of
header files:
set_property(TARGET target APPEND PROPERTY PRECOMPILE_HEADER
boost/spirit/karma.hpp
my/precompiled/header.h
)
changes to source files
---
None. All source files should be written as if there was no PCH
support. That means that each file should include all the headers it
requires. Nothing more, nothing less.
That especially means that source files should *NOT* include an
all.h, precompile.h, or stdafx.h file. Nothing breaks if they
do, but it may impact compile times if precompiled headers are not
supported.
file(s) to precompile
-
Special header files that contain all the system headers may be
created and added to the PRECOMPILE_HEADER property. However, the
system headers may also be added directly to PRECOMPILE_HEADER.
If custom files are created, it is important to note that a special
PCH_SUPPORTED guard is *NOT* required.
What is done behind the scenes
--
CMake creates the actual header file that is going to be precompiled
during the config step inside the current binary directory. The
complete filename encodes the target name and the configuration (eg.
${CMAKE_CURRENT_BINARY_DIR}/${target}_${config}_pch.hpp) and
contains one #include directive for each element in the
PRECOMPILE_HEADER/PRECOMPILE_HEADER_config list. If the element is
wrapped in angle brackets, it is included unmodified, otherwise the
*absolute path* is used in double quotes. The generated header file
for the above example may look like this:
/* generated by CMake 2.8.x */
#include boost/spirit/karma.hpp
#include /home/daniel/workspace/foo/my/precompiled/header.h
This header file is compiled before all object files of the target; ie
the object files depend on the compiled header.
MSVC specific
-
MSVC requires a source file to compile the header. This source file is
generated by CMake alongside the header file and may be called
target_pch.cpp, for example. It contains just one line: an #include
directive that includes the configured header file.
The precompiled header (pch_binary) is created by compiling the source
file (pch_source) with /Yc\${pch_header}\ /Fp\${pch_binary}\.
For the MSVC IDE, pch_binary might be $(IntDir)/${target}.pch.
All other source files are compiled with /Yu\${pch_header}\
/FI\${pch_header}\ /Fp\${pch_binary}\.
/Yc = create pch
/Yu = use pch
/FI = force include
/Fp = name pch binary
GCC specific
In GCC the pch_binary is created by compiling the header file directly
(no extra source file is required). The pch_binary must be
${pch_header}.pch, there is no way to change that. Here, it pays off
again that we generate the actual pch_header in the binary directory.
The compile flags to compile the header are -x c++-header and the
output file must be set with -o ${pch_binary}
All the other source files are compiled with -include ${pch_header}
(force include), it may also be a good idea to pass -Winvalid-pch.
--
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the CMake FAQ at:
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Follow this link to subscribe/unsubscribe:
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Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the CMake FAQ at:
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Follow this link to subscribe/unsubscribe:
