Previously we used separate placeholders for builtin linker flags:
* CMAKE_<LANG>_LINK_FLAGS for EXECUTABLEs
* CMAKE_SHARED_LIBRARY_CREATE_<LANG>_FLAGS for SHARED libraries
* CMAKE_SHARED_MODULE_CREATE_<LANG>_FLAGS for MODULE libraries
These are now always replaced by the empty string, so drop them
from our rule variables.
Variables such as CMAKE_COMPILER_IS_GNUCC are documented as
obsolete/deprecated and ideally shouldn't be used in the code anymore
to have clearer compiler identifications.
In the past QCC compiler was identified as GNU and also had this
variable set to 1 (see policy CMP0047). Same still applies for LCC
compiler (see policy CMP0129).
The linker configuration file is now optional: It is loaded only if
variable CMAKE_<LANG>_USE_LINKER_CONFIGURATION is set to TRUE.
The file CMakeAddNewLanguage.txt is updated to take into account the
linker configuration.
Fixes: #26393
The `Platform/<OS>.cmake` modules record platform-specific flag
variables for the C toolchain. The `CMake<LANG>Information` modules
initialize the per-language platform-specific flag variables to defaults
copied from C. However, they have diverged over time, and not all
platform-specific flag variables are initialized correctly for all
languages. Factor out the CXX language's instance of this logic into a
helper macro, and reuse it for all languages for which we previously
had the platform-specific flag variables at least partially filled out.
Previously the Fortran language's copy of this logic used
`if(NOT DEFINED <var>)` instead of just `if(NOT <var>)` to allow
`Platform/<OS>-<COMPILER_ID>-<LANG>` modules to specify empty values for
some platform-specific flag variables without being overridden.
Use this approach in the helper macro so it applies to all languages.
Fixes: #25990
Currently, this feature is only supported on ELF platforms. So, the property
LINK_WHAT_YOU_USE will be ignored for other plateforms.
Moreover, flags and commands are now controled by CMake variables.
Fixes: #20174
In commit 8d61294c3e (PCH: Mark CMake PCH source files as -x
<lang>-header, 2020-09-04, v3.18.3~14^2) we removed the explicit `-x
objective-c++` flag. This broke cases with custom source extensions.
Restore the explicit `-x objective-c[++]` flag and put it before the
`<FLAGS>` placeholder. The latter will contain the proper `-x
objective-c[++]-header` value and will override the `-x objective-c[++]`
value set before.
Fixes: #21234
Add entries in Modules and Modules/Platform to support
Objective-C compiler determination and identification.
Add Modules to check Objective-C compiler flags, source
compilations, program checks, etc...
Use OBJC as the designator of the language, eg:
project(foo OBJC)
Add various tests for Objective-C language features. Add
tests to preserve C++ handling of .m and .mm files when
OBJC is not a configured language.
Co-Authored-By: Cristian Adam <cristian.adam@gmail.com>
Brad King