more Intel Fortran notes

git-svn-id: https://svn.r-project.org/R/trunk@84705 00db46b3-68df-0310-9c12-caf00c1e9a41

doc/manual/R-admin.texi

@@ -1067,8 +1067,8 @@ Intel compilers. Currently accepted values are (plus some synonyms)
 @example
 g++: c++11 gnu+11 c++14 gnu++14 c++17 gnu++17 c++2a gnu++2a (from 8)
  c++20 gnu++20 (from 10) c++23 gnu++23 c++2b gnu++2b (from 11)
-Intel: c++11 c++14 (from 16.0) c++17 (from 17.0) c++20 (from 2021.1)
- c++23 (from 2022.2)
+Intel: c++11  gnu+11 c++14 gnu++14 c++17 gnu++17
+ c++20 gnu++20 (from 2021.1) c++2b gnu++2b (from 2022.2)
 @end example
 @noindent
 (Those for LLVM @command{clang++} are documented at
@@ -5023,8 +5023,8 @@ supported @cputype{ix86} and 32-bit builds on @cputype{x86_64}.
 The compilers are now all under Intel's `oneAPI' brand. The revamped
 ones are @command{icx}, @command{icpx} and @command{ifx}; the classic
 compilers were @command{icc}, @command{icpc} and @command{ifort}. The
-former are identiifed by the C macro @code{__INTEL_LLVM_COMPILER}, the
-latter by @code{__INTEL_COMPILER}.
+former are identiifed by the C/C++ macro @code{__INTEL_LLVM_COMPILER},
+the latter by @code{__INTEL_COMPILER}.
 
 Standalone installers (which are free-of-charge) are available from
 @uref{https://www.intel.com/content/www/us/en/developer/articles/tool/oneapi-standalone-components.html}:
@@ -5068,15 +5068,23 @@ CXX=$IP/icpc
 FC=$IP/ifort
 CFLAGS="-O3 -ip -fp-model precise"
 FFLAGS="-O3 -fp-model precise"
+FCFLAGS="-free -O3 -fp-model precise"
 CXXFLAGS="-O3 -fp-model precise"
 LDFLAGS="-L/path/to/compilers/compiler/lib/intel64_lin -L/usr/local/lib64"
 @end example
 @noindent
 but also segfaulted in the checks.
 
+One quirk is that the Intel Fortran comoilers do not accept @file{.f95}
+files, only @file{.f90} for free-format Fortran. @command{configure}
+adds @option{-Tf} which tells the compiler this is indeed a Fortran
+file, but @option{-free} is needed to say it is free-format. Hence
+setting the @code{FCFLAGS} macro.
+@c https://www.intel.com/content/www/us/en/docs/fortran-compiler/developer-guide-reference/2023-2/file-extensions.html
+
 There have been no other recent reports on the use of Intel compilers:
 this section is left in case it provides helpful hints for people using
-the 'classic' compilers.
+the 'classic' compilers while they are still available.
 
 Brian Ripley used version 9.0 of the compilers for @cputype{x86_64} on
 Fedora Core 5 with

doc/manual/R-exts.texi

@@ -1228,7 +1228,8 @@ C++@footnote{either or both of which may not be supported on particular
 platforms. Their main use is on macOS, but unfortunately recent
 versions of the macOS SDK have removed much of the support for Objective
 C v1.0 and Objective C++.} with associated extensions @file{.c},
-@file{.cc} or @file{.cpp}, @file{.f}, @file{.f90} or @file{.f95},
+@file{.cc} or @file{.cpp}, @file{.f}, @file{.f90} or
+@file{.f95},@footnote{This is not accepted by the Intel Fortran compiler.}
 @file{.m}, and @file{.mm}, respectively. We recommend using @file{.h}
 for headers, also for C++@footnote{Using @file{.hpp} is not guaranteed
 to be portable.} or Fortran 9x include files. (Use of extension