Expect cxx_variadic_templates to implement N2555.
N2555 is essentially a bugfix and predates most compiler releases which
aimed to experimentally support variadic templates.
Record the availability of this feature for GNU 4.8 on (UNIX AND
NOT APPLE) only. In the future, availability can be recorded for
earlier GNU, for other platforms and for other compilers. Initially
the affected configurations are as restricted as possible to allow
for easy testing while extending the features vector in only one
dimension.
The error message when using the set_property API directly is not
very good, but follow up commits will provide origin debugging of
the property and a target_compile_features command which will
provide a configure-time backtrace when possible.
Use the contents of it to upgrade the CXX_STANDARD target property,
if appropriate. This will have the effect of adding the -std=c++11
compile flag or other language specification on GNU when that is
needed for the feature.
5de63265 Genex: Only evaluate TARGET_OBJECTS to determine target sources.
aa0a3562 cmGeneratorTarget: Compute target objects on demand
042c1c83 cmTarget: Compute languages from object libraries on demand.
fdcefe3c cmGeneratorTarget: Compute consumed object libraries on demand.
c355d108 cmComputeTargetDepends: Track object library depends.
e5da9e51 cmTarget: Allow any generator expression in SOURCES property.
5702e106 cmTarget: Include TARGET_OBJECTS genex in target SOURCES property.
857d30b5 cmGlobalGenerator: Add interface to call ForceLinkerLanguages
28e1d2f8 cmStringCommand: Add GENEX_STRIP subcommand.
bf98cc25 Genex: Evaluate TARGET_OBJECTS as a normal expression.
8cd113ad cmTarget: Store strings instead of cmSourceFile* to represent SOURCES.
4959f341 cmSourceFileLocation: Collapse full path for directory comparisons.
fcc92878 cmSourceFileLocation: Remove unused Update method.
59e8740a cmTarget: Remove AddSourceFile method
26d494ba cmTarget: Use string API to add sources to cmTarget objects.
d38423ec cmTarget: Add a method to obtain list of filenames for sources.
...
This method was added in a commit based on a release branch that
pre-dated the std::string API changes. Port the implementation to use
the string APIs instead of c_str().
These policies are triggered by the use of a particular compiler rather
than outdated CMake code in a project. Avoid warning in every project
that enables a language by not displaying the policy warning by default.
Add variable CMAKE_POLICY_WARNING_CMP<NNNN> to control the warning
explicitly; otherwise enable the warning with --debug-output or --trace.
This breaks with strict policy convention because it does not provide
developers with any warning about the behavior change by default.
Existing projects will continue to build without a warning or change in
behavior. When a developer changes the minimum required version of
CMake in a project to a sufficiently high value (3.0), the project will
suddenly get the new compiler id and may break, but at least the
breakage comes with a change to the project rather than the version of
CMake used to build it.
Breaking strict policy convention is worthwhile in this case because
very few projects will be affected by the behavior change but every
project would have to see the warning if it were enabled by default.
Stephen Kelly
Brad King