--- a/libinterp/corefcn/oct-stream.cc	Mon Sep 27 13:55:27 2021 -0500
+++ b/libinterp/corefcn/oct-stream.cc	Thu Dec 23 19:00:12 2021 +0100
@@ -42,6 +42,7 @@
 #include "Array.h"
 #include "Cell.h"
 #include "byte-swap.h"
+#include "lo-cutils.h"
 #include "lo-ieee.h"
 #include "lo-mappers.h"
 #include "lo-utils.h"
@@ -3897,7 +3898,7 @@
 
     int i;
     int (*compare)(const char *, const char *, std::size_t);
-    compare = (case_sensitive ? strncmp : strncasecmp);
+    compare = (case_sensitive ? strncmp : octave_strncasecmp);
 
     for (i = 0; i < targets.numel (); i++)
       {

--- a/liboctave/external/Faddeeva/Faddeeva.cc	Mon Sep 27 13:55:27 2021 -0500
+++ b/liboctave/external/Faddeeva/Faddeeva.cc	Thu Dec 23 19:00:12 2021 +0100
@@ -140,6 +140,7 @@
                        functions near the origin.  Use gnulib functions
                        if GNULIB_NAMESPACE is defined.
      18 December 2012: Slight tweaks (remove recomputation of x*x in Dawson)
+          12 May 2015: Bugfix for systems lacking copysign function.
 */
 
 /////////////////////////////////////////////////////////////////////////
@@ -200,11 +201,23 @@
 // copysign was introduced in C++11 (and is also in POSIX and C99)
 #  if defined(_WIN32) || defined(__WIN32__)
 #    define copysign _copysign // of course MS had to be different
+#  elif defined(GNULIB_NAMESPACE) // we are using using gnulib <cmath>
+#    define copysign GNULIB_NAMESPACE::copysign
 #  elif (__cplusplus < 201103L) && !defined(HAVE_COPYSIGN) && !defined(__linux__) && !(defined(__APPLE__) && defined(__MACH__)) && !defined(_AIX)
-static inline double my_copysign(double x, double y) { return y<0 ? -x : x; }
+static inline double my_copysign(double x, double y) { return x<0 != y<0 ? -x : x; }
 #    define copysign my_copysign
 #  endif
 
+// If we are using the gnulib <cmath> (e.g. in the GNU Octave sources),
+// gnulib generates a link warning if we use ::floor instead of gnulib::floor.
+// This warning is completely innocuous because the only difference between
+// gnulib::floor and the system ::floor (and only on ancient OSF systems)
+// has to do with floor(-0), which doesn't occur in the usage below, but
+// the Octave developers prefer that we silence the warning.
+#  ifdef GNULIB_NAMESPACE
+#    define floor GNULIB_NAMESPACE::floor
+#  endif
+
 #else // !__cplusplus, i.e., pure C (requires C99 features)
 
 #  include "Faddeeva.h"

--- a/liboctave/operators/Sparse-diag-op-defs.h	Mon Sep 27 13:55:27 2021 -0500
+++ b/liboctave/operators/Sparse-diag-op-defs.h	Thu Dec 23 19:00:12 2021 +0100
@@ -104,9 +104,10 @@
 // FIXME: functors such as this should be gathered somewhere
 template <typename T>
 struct identity_val
-  : public std::unary_function <T, T>
 {
 public:
+  typedef T argument_type;
+  typedef T result_type;
   T operator () (const T x) { return x; }
 };
 

--- a/src/mkoctfile.in.cc	Mon Sep 27 13:55:27 2021 -0500
+++ b/src/mkoctfile.in.cc	Thu Dec 23 19:00:12 2021 +0100
@@ -1201,7 +1201,8 @@
           std::string cmd
             = (vars["F77"] + " -c " + vars["FPICFLAG"] + ' '
                + vars["ALL_FFLAGS"] + ' ' + incflags + ' ' + defs + ' '
-               + pass_on_options + ' ' + f + " -o " + o);
+               + pass_on_options + ' ' + quote_path (f)
+               + " -o " + quote_path (o));
 
           int status = run_command (cmd, verbose, printonly);