Some commands on Windows do not understand forward slash paths and
require backslashes. In order to help projects generate shell
invocations of such commands, provide a generator expression to convert
paths to the shell-preferred path format for the current generator.
This will allow custom commands to generate paths the same way CMake
does for compiler command invocations.
The storage of a pointer means that the ownership and lifetime are
externally determined, which is harder to reason about. It also imposes
API constraints, requiring APIs to return references to backtraces.
This pointer storage was introduced in commit v3.1.0-rc1~425^2~3 (genex:
remove the need for backtraces, 2014-05-23). As backtraces are now cheap
to copy around, just do that instead.
Define an empty string in CMAKE_<LANG>_STANDARD_DEFAULT to mean that
the toolchain has no notion of lanuage standard levels. In this case
the <LANG>_STANDARD[_REQUIRED] properties will have no effect.
Update the RunCMake.CompileFeatures test to exclude the
LinkImplementationFeatureCycle test when there is no standard default.
It can never fail because no use of specific features will adjust the
CXX_STANDARD level required for any target since the standard levels
have no meaning in this case.
Extract a new method to encapsulate the requirements of evaluating
dependent-expressions, namely, propagation of the
EvaluateForBuildsystem setting, which is missing from the
getLinkedTargetsContent implementation.
Commit v3.1.0-rc1~688^2 (Genex: Only evaluate TARGET_OBJECTS to determine
target sources., 2014-03-20) introduced an error case for use of
TARGET_OBJECTS outside of the context of generating the buildsystem,
as the path to object files may be dependent on buildsystem
variables (See bug #15226).
Commit v3.1.0-rc1~314^2 (Allow INTERFACE_SOURCES to specify
$<TARGET_OBJECTS> (#14970), 2014-07-09) made it possible to
propagate such content to dependent targets.
While that commit propagated the EvaluateForBuildsystem setting
for the case of a TARGET_PROPERTY expression, as generated for
direct dependencies of a target in
cmTargetInternals::AddInterfaceEntries, it did not add propagation
for content from further transitive target dependencies, as determined
by getLinkedTargetsContent.
The evaluation files must be known before cmTargetTraceDependencies
attempts to find them, but we must actually generate the files after
cmTargetTraceDependencies, as that can add to target SOURCES. The
limitation is that the generated output name must not depend on the
SOURCES of a target if the generated file is used by that target.
Mark the output files as GENERATED so that trace dependencies does
not expect them to already exist in the filesystem.
Move the invokation of ForceLinkerLanguage in the Generate logic
to after the generated file names are known. ForceLinkerLanguage
tries to determine the sources of a target (in order to determine
an already-known language) and otherwise fails to get information
about the generated file.
Test that the output of file(GENERATE) can be used as a target source
file and that accessing the target SOURCES in the name of the output
file is an error. Accessing the TARGET_OBJECTS would be a similar
error if it was legal to use that generator expression in this
context. That is not currently possible and is a different error
condition, so test the current error output as a reminder to change
the expected output if that becomes possible in the future. Test
that generated rule files resulting from cmTargetTraceDependencies
appear in the SOURCES generated in the output file.
Stephen Kelly