Revert commit 74b1c9fc8e (Explicitly specify language flag when source
LANGUAGE property is set, 2020-06-01, v3.19.0-rc1~722^2) and the lookup
tables from its two immediate ancestors. The purpose of that change was
to convert an explicit `LANGUAGE` source file property into an explicit
language specification compiler flag like `-x c`. This seems reasonable
since the property is documented as meaning "indicate what programming
language the source file is". It is also needed to help compilers deal
with non-standard source file extensions they don't recognize.
However, some projects have been setting `LANGUAGE C` on `.S` assembler
source files to mean "use the C compiler". Passing `-x c` for them
breaks the build because the `.S` sources are not written in C. These
projects should be updated to use `enable_language(ASM)`, for which
CMake often chooses the C compiler as the assembler when using
toolchains that support it (which would have to be the case for projects
using the approach).
Revert the change for now to preserve the old behavior for such projects.
We can re-introduce it with a policy in a future version of CMake.
Fixes: #21469
Issue: #14516, #20716
Since commit b0f46c48f6 (CompileFeatures: Now able to presume full
language level support, 2019-03-06, v3.15.0-rc1~265^2~1) we pretend that
the XL compiler has full C++11 and C++14 support so that projects
specifying granular features will at least get the corresponding
compiler mode. This is a work around for our lack of a full feature
check table for this compiler that works in common cases. Add a comment
explaining this.
Issue: #20521
Since commit 458ea9d76c (XL: Add C++14 language level flags, 2019-04-15,
v3.15.0-rc1~226^2) we use `-qlanglvl=extended1y` for C++14 with XL 16.1.
However, that flag is only supported on a Linux host.
Issue: #20521
Previously compilers that only supported the meta-level flags
would not have any of the granular features listed. Now we
presume that they have full support and enable all the features.
Update granular feature tests to skip the actual compilation
checks for the presumed features.
In commit 6555286c55 (XL: Add C and C++ language level flags,
2017-04-27, v3.9.0-rc1~184^2) we added support for both the traditional
XL compiler and the Clang-based variant used on Linux. The latter is
now handled by `Modules/Compiler/XLClang-{C,CXX}.cmake` using the
`XLClang` compiler id. Drop the corresponding content from the
traditional XL compiler modules.
The valid settings to pass to the IBM XL compiler for the -qhalt flag
vary widely by language and platform. Based on existing documentation,
the following table shows which error levels are valid to pass to
-qhalt= since -qhalt=e is not always available.
OS | xlc | xlC | xlf |
---------|-------|------------------
AIX | iwes | iw s | ilwesu |
BlueGene | iwes | iwes | ilwesu |
OS X | iwesu | iwesu | ilwesu |
Linux | w | w | ilwesu |
Document these variables.
Change our convention for setting these variables from:
set(CMAKE_C_FLAGS_INIT "...")
to
string(APPEND CMAKE_C_FLAGS_INIT " ...")
so that any value previously set by a toolchain file will be used.
Automate the conversion with:
sed -i 's/set *(\(CMAKE_\(C\|CXX\|Fortran\|RC\|ASM\|${[^}]\+}\)_FLAGS\(_[^_]\+\)\?_INIT \+"\)/string(APPEND \1 /' \
Modules/Compiler/*.cmake Modules/Platform/*.cmake
and follow up with some manual fixes (e.g. to cases that already
meant to append). Also revert the automated changes to contexts
that are not protected from running multiple times.
Teach the Makefile and Ninja generators to substitute for an <INCLUDES>
placeholder instead of putting -I in <FLAGS>. Update our values for
CMAKE_<LANG>_COMPILE_OBJECT,
CMAKE_<LANG>_CREATE_ASSEMBLY_SOURCE, and
CMAKE_<LANG>_CREATE_PREPROCESSED_SOURCE
to place <INCLUDES> just before <FLAGS>.
Factor duplicate information out of Compiler/XL-<lang>.cmake modules
into a macro in a new Compiler/XL.cmake module. Invoke it from the
per-language files to produce the original settings.
Since commit e1729238 (Add initial XL C compiler flags for safer builds,
2009-09-30) CMake sets the initial XL C flags to include "-qthreaded"
and "-qhalt=e". Do the same for C++ and Fortran with this toolchain.
This moves platform-independent XL compiler flags into separate
"Compiler/XL-<lang>.cmake" modules. Platform-specific flags go in
"Platform/<os>-XL-<lang>.cmake" modules.
IBM rebranded its VisualAge compiler to XL starting at version 8.0. We
use the compiler id "XL" for newer versions and "VisualAge" for older
versions. We now also recognize the "z/OS" compiler, which is distinct
from XL.
