This can be allowed in the next release, but it needs to have some
features present and tested such as
* Ensuring that relative paths do not appear in the generated property.
* Ensuring that paths to the source or build directories do not appear.
* Generating a check in the file for CMake 3.1 or later so that the
resulting property will be consumed.
* Ensuring that any referenced targets are part of an export set and
generating a check for them.
* INSTALL_INTERFACE and BUILD_INTERFACE content.
All of these checks are already done for INTERFACE_INCLUDE_DIRECTORIES,
but it is too late to add them for INTERFACE_SOURCES for CMake 3.1.
As the checks introduce some new error conditions, it is better to
disallow exporting fully for this case and introduce proper error
conditions later instead of policies.
Follow the pattern of checks that are made for INTERFACE_INCLUDE_DIRECTORIES.
Existence is already checked by cmSourceFile::GetFullPath. Add a check
to disallow relative paths in source directories. Otherwise code such as
target_sources(lib1 INTERFACE foo.cpp)
would fail if consumed by a target in a different directory.
Unlike the INTERFACE_INCLUDE_DIRECTORIES behavior, we don't care whether
the entry comes from an IMPORTED target or not. In the include directories
case, the directory for a non-imported target might not exist yet but
might be created. In the sources case, a file which does not yet
exist in the filesystem must be explicitly marked with the GENERATED
property.
Adjust existing tests and add a new test for the error.
Xcode 1.5 does not support multiple configurations. The generator also
adds some sources internally that cause extra OriginDebug output.
Update the expected output to tolerate it.
Since commit e5da9e51 (cmTarget: Allow any generator expression in
SOURCES property., 2014-03-18), source files are computed by
true evaluation of generator expressions, including TARGET_OBJECTS.
This evaluation requires the presence of cmGeneratorTarget objects
since commit bf98cc25 (Genex: Evaluate TARGET_OBJECTS as a normal
expression., 2014-02-26).
Ensure that we don't attempt to evaluate the TARGET_OBJECTS generator
expression at configure-time, as can happen if CMP0024 or CMP0026
are OLD. Use old-style parsing of the source item to extract
object target names in that case.
Avoid calling GetProperty("SOURCES") to bypass warnings from CMP0051.
Refactor existing logic in GetLanguages which is similar in intent to
the new GetSourceFiles code.
Disallow the use of config-specific source files with
the Visual Studio and Xcode generators. They don't have
any way to represent the condition currently.
Use the same common-config API in cmQtAutoGenerators. While
it accepts config-specific files, it doesn't have to support
multiple configurations yet.
Loop over the configs in cmTargetTraceDependencies
and cmGlobalGenerator::WriteSummary and consume all source
files.
Loop over the configs in cmComputeTargetDepends and compute the
object library dependencies for each config.
Stephen Kelly
Brad King