The PGI ( and NVIDIA HPC ) compilers default C++ standard level
are based on the GCC system headers it is compiling against.
Therefore on newer platforms the default C++ level will be >= 11
and requesting C++98 compilation mode will fail as no explicit
flag will be set.
Since commit 9b97cb5562 (PGI: Add language standards for PGI,
2017-05-01, v3.9.0-rc1~174^2), we have passed the `-A` flag to
the PGI C++ compiler when specifying a C++ standard flag with
compiler extensions turned off. The flag is not meant for that.
The PGI C++ standard flags do not turn extensions on by default
and have a separate `--gnu_extensions` flag for that which we
already use when CXX_EXTENSIONS is ON. Simply drop the `-A` flag.
Fixes: #20997
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.
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.
We factor flags from Platform/Linux-PGI-Fortran.cmake into language
independent helper modules
Compiler/PGI.cmake
Platform/Linux-PGI.cmake
and invoke the macros from
Compiler/PGI-<lang>.cmake
Platform/Linux-PGI-<lang>.cmake
This enables general support for the PGI compilers.
We set the variables to contain "-v", the verbose front-end output
option for PGI compilers. This enables detection of implicit link
libraries and directories for these compilers.
