Improve coverage of cpluspluscheck.

Formerly, cpluspluscheck was only meant to examine headers that
we thought of as exported --- but its notion of what we export
was well behind the times.  Let's just make it check *all* .h
files, except for a well-defined blacklist, instead.

While at it, improve its ability to use a C++ compiler other than g++,
by scraping the CXX setting from Makefile.global and making it possible
to override the warning options used (per suggestion from Andres Freund).

Discussion: https://postgr.es/m/b517ec3918d645eb950505eac8dd434e@gaz-is.ru

src/tools/pginclude/cpluspluscheck

@@ -1,12 +1,12 @@
 #!/bin/sh
 
-# Check all exported PostgreSQL include files for C++ compatibility.
+# Check (almost) all PostgreSQL include files for C++ compatibility.
 #
 # Argument 1 is the top-level source directory, argument 2 the
 # top-level build directory (they might be the same). If not set, they
 # default to the current directory.
 #
-# Needs to be run after all generated headers are created.
+# Needs to be run after configuring and creating all generated headers.
 #
 # No output if everything is OK, else compiler errors.
 
@@ -17,44 +17,132 @@ else
 fi
 
 if [ -z "$2" ]; then
-    builddir="$."
+    builddir="."
 else
     builddir="$2"
 fi
 
 me=`basename $0`
 
+# Pull some info from configure's results.
+MGLOB="$builddir/src/Makefile.global"
+CXX=`sed -n 's/^CXX[ 	]*=[ 	]*//p' "$MGLOB"`
+perl_includespec=`sed -n 's/^perl_includespec[ 	]*=[ 	]*//p' "$MGLOB"`
+python_includespec=`sed -n 's/^python_includespec[ 	]*=[ 	]*//p' "$MGLOB"`
+
+# These switches are g++ specific, you may override if necessary.
+CXXFLAGS=${CXXFLAGS:- -fsyntax-only -Wall}
+
+# Create temp directory.
 tmp=`mktemp -d /tmp/$me.XXXXXX`
 
 trap 'rm -rf $tmp' 0 1 2 3 15
 
-# Omit src/include/port/, because it's platform specific, and c.h includes
+# Scan all of src/ and contrib/ for header files.
-# the relevant file anyway.
+for f in `cd "$srcdir" && find src contrib -name '*.h' -print`
-# rusagestub.h is also platform-specific, and will be included by
+do
-# utils/pg_rusage.h if necessary.
+	# Ignore files that are unportable or intentionally not standalone.
-# access/rmgrlist.h is not meant to be included standalone.
+
-# regex/regerrs.h is not meant to be included standalone.
+	# These files are platform-specific, and c.h will include the
-# parser/gram.h will be included by parser/gramparse.h.
+	# one that's relevant for our current platform anyway.
-# parser/kwlist.h is not meant to be included standalone.
+	test "$f" = src/include/port/aix.h && continue
+	test "$f" = src/include/port/cygwin.h && continue
+	test "$f" = src/include/port/darwin.h && continue
+	test "$f" = src/include/port/freebsd.h && continue
+	test "$f" = src/include/port/hpux.h && continue
+	test "$f" = src/include/port/linux.h && continue
+	test "$f" = src/include/port/netbsd.h && continue
+	test "$f" = src/include/port/openbsd.h && continue
+	test "$f" = src/include/port/solaris.h && continue
+	test "$f" = src/include/port/win32.h && continue
+
+	# Additional Windows-specific headers.
+	test "$f" = src/include/port/win32_port.h && continue
+	test "$f" = src/include/port/win32/sys/socket.h && continue
+	test "$f" = src/include/port/win32_msvc/dirent.h && continue
+	test "$f" = src/port/pthread-win32.h && continue
+
+	# Likewise, these files are platform-specific, and the one
+	# relevant to our platform will be included by atomics.h.
+	test "$f" = src/include/port/atomics/arch-arm.h && continue
+	test "$f" = src/include/port/atomics/fallback.h && continue
+	test "$f" = src/include/port/atomics/generic.h && continue
+	test "$f" = src/include/port/atomics/generic-acc.h && continue
+	test "$f" = src/include/port/atomics/generic-gcc.h && continue
+	test "$f" = src/include/port/atomics/generic-msvc.h && continue
+	test "$f" = src/include/port/atomics/generic-xlc.h && continue
+
+	# rusagestub.h is also platform-specific, and will be included
+	# by utils/pg_rusage.h if necessary.
+	test "$f" = src/include/rusagestub.h && continue
+
+	# sepgsql.h depends on headers that aren't there on most platforms.
+	test "$f" = contrib/sepgsql/sepgsql.h && continue
+
+	# These files are not meant to be included standalone, because
+	# they contain lists that might have multiple use-cases.
+	test "$f" = src/include/access/rmgrlist.h && continue
+	test "$f" = src/include/parser/kwlist.h && continue
+	test "$f" = src/pl/plpgsql/src/pl_reserved_kwlist.h && continue
+	test "$f" = src/pl/plpgsql/src/pl_unreserved_kwlist.h && continue
+	test "$f" = src/interfaces/ecpg/preproc/c_kwlist.h && continue
+	test "$f" = src/interfaces/ecpg/preproc/ecpg_kwlist.h && continue
+	test "$f" = src/include/regex/regerrs.h && continue
+	test "$f" = src/pl/plpgsql/src/plerrcodes.h && continue
+	test "$f" = src/pl/plpython/spiexceptions.h && continue
+	test "$f" = src/pl/tcl/pltclerrcodes.h && continue
+
+	# We can't make these Bison output files compilable standalone
+	# without using "%code require", which old Bison versions lack.
+	# parser/gram.h will be included by parser/gramparse.h anyway.
+	test "$f" = src/include/parser/gram.h && continue
+	test "$f" = src/backend/parser/gram.h && continue
+	test "$f" = src/pl/plpgsql/src/pl_gram.h && continue
+	test "$f" = src/interfaces/ecpg/preproc/preproc.h && continue
+
+	# ppport.h is not under our control, so we can't make it standalone.
+	test "$f" = src/pl/plperl/ppport.h && continue
+
+	# regression.h is not actually C, but ECPG code.
+	test "$f" = src/interfaces/ecpg/test/regression.h && continue
+
 	# pg_trace.h and utils/probes.h can include sys/sdt.h from SystemTap,
 	# which itself contains C++ code and so won't compile with a C++
 	# compiler under extern "C" linkage.
+	test "$f" = src/include/pg_trace.h && continue
+	test "$f" = src/include/utils/probes.h && continue
 
-for f in `cd "$srcdir" && find src/include src/interfaces/libpq/libpq-fe.h src/interfaces/libpq/libpq-events.h -name '*.h' -print | \
+	# pg_dump is not C++-clean because it uses "public" and "namespace"
-    grep -v -e ^src/include/port/ \
+	# as field names, which is unfortunate but we won't change it now.
-	-e ^src/include/rusagestub.h -e ^src/include/regex/regerrs.h \
+	test "$f" = src/bin/pg_dump/compress_io.h && continue
-	-e ^src/include/access/rmgrlist.h \
+	test "$f" = src/bin/pg_dump/parallel.h && continue
-	-e ^src/include/parser/gram.h -e ^src/include/parser/kwlist.h \
+	test "$f" = src/bin/pg_dump/pg_backup_archiver.h && continue
-	-e ^src/include/pg_trace.h -e ^src/include/utils/probes.h`
+	test "$f" = src/bin/pg_dump/pg_dump.h && continue
-do
+
+	# OK, create .c file to include this .h file.
 	{
 	    echo 'extern "C" {'
-	    test $f != "src/include/postgres_fe.h" && echo '#include "postgres.h"'
+	    test "$f" != src/include/postgres_fe.h && echo '#include "postgres.h"'
 	    echo "#include \"$f\""
 	    echo '};'
 	} >$tmp/test.cpp
 
-	${CXX:-g++} -I $srcdir -I $srcdir/src/interfaces/libpq -I $srcdir/src/include \
+	# Some subdirectories need extra -I switches.
-		    -I $builddir -I $builddir/src/interfaces/libpq -I $builddir/src/include \
+	case "$f" in
-		    -fsyntax-only -Wall -c $tmp/test.cpp
+	    src/pl/plperl/*)
+		EXTRAINCLUDES="$perl_includespec" ;;
+	    src/pl/plpython/*)
+		EXTRAINCLUDES="$python_includespec" ;;
+	    src/interfaces/ecpg/*)
+		EXTRAINCLUDES="-I $builddir/src/interfaces/ecpg/include -I $srcdir/src/interfaces/ecpg/include" ;;
+	    *)
+		EXTRAINCLUDES="" ;;
+	esac
+
+	# Run the test.
+	${CXX:-g++} -I $builddir -I $srcdir \
+		-I $builddir/src/include -I $srcdir/src/include \
+		-I $builddir/src/interfaces/libpq -I $srcdir/src/interfaces/libpq \
+		$EXTRAINCLUDES $CXXFLAGS -c $tmp/test.cpp
+
 done