XL: Add support for Ninja and XL Fortran

The Ninja generator's support for Fortran requires that source files
be preprocessed explicitly first.  However, the `xlf` compiler does
not have a simple `-E` option or equivalent to do preprocessing.
The only documented way to get preprocessed output is to use `-d`
to leave it behind, but only at an inflexible location.

Instead, create our own `cpp` wrapper script and substitute it for the
real preprocessor using `-tF -B ...`.  Teach the wrapper to map the
`cpp` output to the location we need and then invoke the real `cpp`
underneath.

Fixes: #19450

2 files changed, 33 insertions, 0 deletions

diff --git a/Modules/Compiler/XL-Fortran.cmake b/Modules/Compiler/XL-Fortran.cmake
index c4fb097..1683dff 100644
--- a/Modules/Compiler/XL-Fortran.cmake
+++ b/Modules/Compiler/XL-Fortran.cmake
@@ -18,3 +18,7 @@ string(APPEND CMAKE_Fortran_FLAGS_INIT " -qthreaded -qhalt=e")
 # xlf: 1501-214 (W) command option E reserved for future use - ignored
 set(CMAKE_Fortran_CREATE_PREPROCESSED_SOURCE)
 set(CMAKE_Fortran_CREATE_ASSEMBLY_SOURCE)
+
+set(CMAKE_Fortran_PREPROCESS_SOURCE
+  "<CMAKE_Fortran_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -qpreprocess -qnoobject -qsuppress=1517-020 -tF -B \"${CMAKE_CURRENT_LIST_DIR}/XL-Fortran/\" -WF,--cpp,\"${CMAKE_Fortran_XL_CPP}\",--out,<PREPROCESSED_SOURCE> <SOURCE>"
+  )
diff --git a/Modules/Compiler/XL-Fortran/cpp b/Modules/Compiler/XL-Fortran/cpp
new file mode 100755
index 0000000..1fd62c2
--- /dev/null
+++ b/Modules/Compiler/XL-Fortran/cpp
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+# Source file.
+src="$(printf %q "$1")"
+shift
+
+# Output file the compiler expects.
+out="$(printf %q "$1")"
+shift
+
+# Create the file the compiler expects.  It will check syntax.
+>"$out"
+
+cpp='cpp'
+opts=''
+while test "$#" != 0; do
+    case "$1" in
+    # Extract the option for the path to cpp.
+    --cpp) shift; cpp="$(printf %q "$1")" ;;
+    # Extract the option for our own output file.
+    --out) shift; out="$(printf %q "$1")" ;;
+    # Collect the rest of the command line.
+    *) opts="$opts $(printf %q "$1")" ;;
+    esac
+    shift
+done
+
+# Execute the real preprocessor tool.
+eval "exec $cpp $src $out $opts"