In commit v3.4.0-rc1~18^2 (Disable shared library support when compiler
links statically, 2015-09-30) we tried to detect when the compiler is
not capable of linking shared libraries (possibly due to flags in use).
However, the approach is not robust against flags like `-nostdlib`.
Revert it for now pending another solution to the original problem.

When a user or a compiler wrapper adds '-static' to the compiler flags
then it will always link static binaries.  Detect this from the compiler
id binary and disable TARGET_SUPPORTS_SHARED_LIBS.  This will prevent
projects from accidentally adding shared libraries when the toolchain
does not support them.  It also helps CMake avoid linking with flags
that require shared libraries to be supported.

Move detection over to the compiler id logic where we have already
constructed the list of compiler flags from ARG1 and CMAKE_<LANG>_FLAGS.
Pass the flags when we execute "cl" with "/showIncludes".  Also pass "/c"
because we only need to compile, not link.  Check the compiler process
exit code before trusting its output.

This executable comes with CMake so just compute its location in
cmSystemTools instead of storing it in compiler information modules.

Use the __cplusplus and __STDC_VERSION__ macros to automatically
determine the default dialect for the compiler while determining its
id and version.

Add properties and variables corresponding to CXX equivalents.

Add features for c_function_prototypes (C90), c_restrict (C99),
c_variadic_macros (C99) and c_static_assert (C11). This feature
set can be extended later.

Add a <PREFIX>_RESTRICT symbol define to WriteCompilerDetectionHeader
to conditionally represent the c_restrict feature.

Objective C sources should be compiled with the C compiler, not C++.

The Xcode generator correctly classifies ".m" sources already.  The
cmSystemTools::GetFileFormat method was fixed by commit v2.8.0~1782 (fix
for 7045, use gcc for .m, 2008-08-19) but it is not used by any of the
generator since commit v2.4.0~2819 (major changes to support addition of
languages, 2004-09-22).

Fix the CMAKE_<LANG>_SOURCE_FILE_EXTENSIONS table entries so that
cmGlobalGenerator::GetLanguageFromExtension tells the Makefile, Ninja,
and VS IDE generators to compile ".m" sources as C.  This makes behavior
consistent on all generators.
Signed-off-by: Tim Blechmann <tim@klingt.org>

cmcldeps is now only used for .rc file processing

Some compilers try to simulate other compilers as a drop-in replacement
supporting all the same command-line options and predefined preprocessor
macros.  In such cases it will be useful to have CMake load the compiler
information files for the simulated compiler instead of duplicating the
information.  Teach CMakeDetermineCompilerId to extract the simulated
compiler id and version when the compiler id detection provides it.

Previously we hard-coded a list of implicit framework directories but
did not account for CMAKE_OSX_SYSROOT or for changes to the list across
OS X versions.  Instead we should automatically detect the framework
directories for the active toolchain.

The parent commit added the "-Wl,-v" option to ask "ld" to print its
implicit directories.  It displays a block such as:

 Framework search paths:
	/...

Parse this block to extract the list of framework directories.

Detection may fail on toolchains that do not list their framework
directories, such as older OS X linkers.  Always treat the paths

 <sdk>/Library/Frameworks
 <sdk>/System/Library/Frameworks
 <sdk>/Network/Library/Frameworks # Older OS X only
 /System/Library/Frameworks

as implicit.  Note that /System/Library/Frameworks should always be
considered implicit so that frameworks CMake finds there will not
override the SDK copies.

Drop the last use of CMAKE_OSX_SYSROOT_DEFAULT.  Replace internal
platform variable CMAKE_${lang}_HAS_ISYSROOT with a more general
CMAKE_${lang}_SYSROOT_FLAG variable.  If the -isysroot flag exists and
CMAKE_OSX_SYSROOT points to an SDK (not "/") then always add it to
compiler command lines.  This is already done in the Xcode IDE.

Drop use of cache entry CMAKE_DETERMINE_<LANG>_ABI_COMPILED and replace
it with variable CMAKE_<LANG>_ABI_COMPILED.  Since the grandparent
commit this test result is specific to the version of CMake.  Store it
in the version-specific compiler information files instead of
CMakeCache.txt so testing can be re-done to meet the requirements of the
current version of CMake even if another version of CMake was already
used to configure the build tree.

Since the parent commit this test result is specific to the version of
CMake.  Store it in the version-specific compiler information files
instead of CMakeCache.txt so testing can be re-done to meet the
requirements of the current version of CMake even if another version of
CMake was already used to configure the build tree.

Ancient versions of CMake required else(), endif(), and similar block
termination commands to have arguments matching the command starting the
block.  This is no longer the preferred style.

Run the following shell code:

for c in else endif endforeach endfunction endmacro endwhile; do
    echo 's/\b'"$c"'\(\s*\)(.\+)/'"$c"'\1()/'
done >convert.sed &&
git ls-files -z -- bootstrap '*.cmake' '*.cmake.in' '*CMakeLists.txt' |
egrep -z -v '^(Utilities/cm|Source/kwsys/)' |
egrep -z -v 'Tests/CMakeTests/While-Endwhile-' |
xargs -0 sed -i -f convert.sed &&
rm convert.sed

Ancient CMake versions required upper-case commands.  Later command
names became case-insensitive.  Now the preferred style is lower-case.

Run the following shell code:

cmake --help-command-list |
grep -v "cmake version" |
while read c; do
    echo 's/\b'"$(echo $c | tr '[:lower:]' '[:upper:]')"'\(\s*\)(/'"$c"'\1(/g'
done >convert.sed &&
git ls-files -z -- bootstrap '*.cmake' '*.cmake.in' '*CMakeLists.txt' |
egrep -z -v '^(Utilities/cm|Source/kwsys/)' |
xargs -0 sed -i -f convert.sed &&
rm convert.sed

And make /showIncude prefix visible for all build rules

Teach CMakePlatformId.h to construct an "INFO:compiler_version[]" string
literal from macros COMPILER_VERSION_(MAJOR|MINOR|PATCH|TWEAK) to be
defined in CMake(C|CXX)CompilerId.(c|cpp) for each compiler.  Provide
conversion macros DEC() and HEX() to decode decimal or hex digits from
integer values.  Parse the version out of the compiler id binary along
with the other INFO values already present.

Store the result in variable CMAKE_<LANG>_COMPILER_VERSION in the format
"major[.minor[.patch[.tweak]]]".  Save the value persistently in
CMake(C|CXX)Compiler.cmake in the build tree.  Document the variable for
internal use since we do not set it everywhere yet.

Report the compiler version on the compiler id result line e.g.

  The C compiler identification is GNU 4.5.2

Report CMAKE_(C|CXX)_COMPILER_(ID|VERSION) in SystemInformation test.

Implement support for multiarch as specified here:

  http://wiki.debian.org/Multiarch
  https://wiki.ubuntu.com/MultiarchSpec

Detect the <arch> part of <prefix>/lib/<arch> from the implicit library
search path from each compiler to set CMAKE_<lang>_LIBRARY_ARCHITECTURE.
Define CMAKE_LIBRARY_ARCHITECTURE using one of these values (they should
all be the same).  Teach the find_library and find_package commands to
search <prefix>/lib/<arch> whenever they would search <prefix>/lib.

Fix issue #10155 - default value of CMAKE_OSX_DEPLOYMENT_TARGET should always be the empty string. When the value of CMAKE_OSX_DEPLOYMENT_TARGET is the empty string, the -mmacosx-version-min flag should not show up on the compiler command line. The logic for selecting default value of CMAKE_OSX_SYSROOT is orthogonal to and independent of the value of the deployment target. The default value for CMAKE_OSX_SYSROOT is the SDK that corresponds to the current version of Mac OSX on which cmake is running.

This is already done for assembler and is necessary for e.g. Symbian.

Alex

Change the way 32/64 bit compiles are detected with MSVC and intel makefile builds. Use the platform ID preprocessor approach.

Previously we checked for this flag by parsing the version number of GCC
out of 'gcc --version', but this is not reliable because the format can
vary greatly.  Now we run 'gcc -v --help' and look for '-isysroot' in
the list of options.

We also now store the result on a per-language basis in the per-compiler
info file "CMake<LANG>Compiler.cmake".  This is necessary to make it
accessible from try-compile projects so that they generate correctly.

This teaches CMake to detect implicit link information for C, C++, and
Fortran compilers.  We detect the implicit linker search directories and
implicit linker options for UNIX-like environments using verbose output
from compiler front-ends.  We store results in new variables called

  CMAKE_<LANG>_IMPLICIT_LINK_LIBRARIES
  CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES

The implicit libraries can contain linker flags as well as library
names.

ENH: second try for handling the linker language with integer priority values (returning a pointer to a string on the stack is no good idea)

Alex

Alex

ENH: CMAKE_<LANG>_LINKER_PREFERENCE is now an integer priority, not a
two-step priority (None or Prefered)
Current order: ASM 0, C 10, Fortran 20, CXX 30, Java 40
This is the same order as automake choses:
http://www.gnu.org/software/automake/manual/html_node/How-the-Linker-is-Chosen.html

This change should be backward compatible:
if there is a project using fortran and CXX, they had to set the
LINKER_LANGUAGE explicitely, otherwise cmake complained (but still generated
the project files). Explicitely setting the linker language still overrides
automatic detection.
If somebody has a custom language for cmake and the PREFERENCE starts with
"P", its changed to 100, which gives it preference over all other languages
(except the other custom languages which have also "Prefered"). "None" is
converted to 0.

Alex

ENH: split cmGlobalGenerator::SetLanguageEnabled() in two parts, where the
second part copies the values from the cmake variables into internal maps.
So this can now be done after the compiler-specific information has been
loaded, which can now overwrite more settings.

Alex

ENH: merge CMake-CrossCompileBasic to HEAD
-add a RESULT_VARIABLE to INCLUDE()
-add CMAKE_TOOLCHAIN_FILE for specifiying your (potentially crosscompiling) toolchain
-have TRY_RUN() complain if you try to use it in crosscompiling mode (which were compiled but cannot run on this system)
-use CMAKE_EXECUTABLE_SUFFIX in TRY_RUN(), probably TRY_RUN won't be able to
run the executables if they have a different suffix because they are
probably crosscompiled, but nevertheless it should be able to find them
-make several cmake variables presettable by the user: CMAKE_C/CXX_COMPILER, CMAKE_C/CXX_OUTPUT_EXTENSION, CMAKE_SYSTEM_NAME, CMAKE_SYSTEM_INFO_FILE
-support prefix for GNU toolchains (arm-elf-gcc, arm-elf-ar, arm-elf-strip etc.)
-move ranlib on OSX from the file command to a command in executed in cmake_install.cmake
-add support for stripping during install in cmake_install.cmake
-split out cl.cmake from Windows-cl.cmake, first (very incomplete) step to support MS crosscompiling tools
-remove stdio.h from the simple C program which checks if the compiler works, since this may not exist for some embedded platforms
-create a new CMakeFindBinUtils.cmake which collects the search fro ar, ranlib, strip, ld, link, install_name_tool and other tools like these
-add support for CMAKE_FIND_ROOT_PATH for all FIND_XXX commands, which is a
list of directories which will be prepended to all search directories, right
now as a cmake variable, turning it into a global cmake property may need
some more work
-remove cmTestTestHandler::TryExecutable(), it's unused
-split cmFileCommand::HandleInstall() into slightly smaller functions

Alex

ENH: Merging CompilerId implementation from branch CMake-Modules-CompilerId to the main tree.  Changes between CMake-Modules-CompilerId-bp and CMake-Modules-CompilerId-mp1 are included.