For historical reasons we still support naming of source files without
their extension. Sources without known extensions are located on disk
by iterating through a fixed set of possible extensions. We now want
users to always specify the extension, so the fixed set will not be
expanded and is preserved for compatibility with older projects.
This change adds recognition of extensions of all enabled languages to
avoid checking the disk for files whose extensions are unambiguous but
not in the original fixed set.
In CMake 2.4 the generated link line for a target always preserved the
originally specified libraries in their original order. Dependencies
were satisfied by inserting extra libraries into the line, though it had
some bugs. In CMake 2.6.0 we preserved only the items on the link line
that are not known to be shared libraries. This reduced excess
libraries on the link line. However, since we link to system libraries
(such as /usr/lib/libm.so) by asking the linker to search (-lm), some
linkers secretly replace the library with a static library in another
implicit search directory (developers can override this by using an
imported target to force linking by full path). When this happens the
order still matters.
To avoid this and other potential subtle issues this commit restores
preservation of all non-target items and static library targets. This
will create cases of unnecessary, duplicate shared libraries on the link
line if the user specifies them, but at least it will work. In the
future we can attempt a more advanced analysis to safely remove
duplicate shared libraries from the link line.
We preserve the order and multiplicity of libraries directly linked by a
target as specified by the user. Items known to be shared libraries may
be safely skipped because order preservation is only needed for static
libraries. However, CMake 2.4 did not skip shared libs, so we do the
same when in 2.4 compatibility mode.
We never explicitly specify system library directories in linker or
runtime search paths. Furthermore, libraries in these directories are
always linked by asking the linker to search for them. We need to
generate a warning when explicitly specified search directories contain
files that may hide the system libraries during the search.
This change introduces policy CMP0008 to decide how to treat full path
libraries that do not appear to be valid library file names. Such
libraries worked by accident in the VS IDE and Xcode generators with
CMake 2.4 and below. We support them in CMake 2.6 by introducing this
policy. See policy documentation added by this change for details.
Sometimes we ask the linker to search for a library for which the path
is known but for some reason cannot be specified by full path. In these
cases do not include the library in CMP0003 warnings because we know the
extra paths are not needed for it.
- This case worked accidentally in CMake 2.4, though not in Makefiles.
- Some projects build only with the VS IDE on windows and have this
mistake.
- Support them when 2.4 compatibility is enabled by adding the extension.
CMAKE[_SYSTEM]_(LIBRARY|PROGRAM|INCLUDE|PREFIX)_PATH variables
-moved CMAKE_CROSSCOMPILING from "Variables that modify behaviour" to
"variables that Provide Information", since it should be used only for
testing whether we are currently in cross compiling mode, not for switching
between the modes.
Alex
- The source-file signature of try_compile looks up the language
of the source file using the extension-to-language map so that
it knows what language to enable in the generated project.
- This map needs to be filled before loading a file specified by
CMAKE_USER_MAKE_RULES_OVERRIDE
CMAKE_USER_MAKE_RULES_OVERRIDE_<LANG>
so that the user file may call the try_compile() source-file
signature.
- It must still be re-filled after loading CMake<LANG>Information.cmake
in case the compiler- or platform-specific files added anything.
- See bug #7340.
David Cole
Bill Hoffman
Brad King
Alexander Neundorf