return early for zero-sized arrays

pocketfft_hdronly.h

 /*
- * This file is part of pocketfft.
- * Licensed under a 3-clause BSD style license - see LICENSE.md
- */
-
-/*
- *  Main implementation file.
- *
- *  Copyright (C) 2004-2019 Max-Planck-Society
- *  \author Martin Reinecke
- */
+This file is part of pocketfft.
+
+Copyright (C) 2010-2019 Max-Planck-Society
+Author: Martin Reinecke
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+* Redistributions in binary form must reproduce the above copyright notice, this
+  list of conditions and the following disclaimer in the documentation and/or
+  other materials provided with the distribution.
+* Neither the name of the copyright holder nor the names of its contributors may
+  be used to endorse or promote products derived from this software without
+  specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
 
 #ifndef POCKETFFT_HDRONLY_H
 #define POCKETFFT_HDRONLY_H
 
+#ifndef __cplusplus
+#error This file is C++ and requires a C++ compiler
+#endif
+
+#if __cplusplus < 201103L
+#error This file requires at least C++11 support
+#endif
+
 #include <cmath>
 #include <cstring>
 #include <cstdlib>
@@ -2409,6 +2437,7 @@ template<typename T> void c2c(const shape_t &shape, const stride_t &stride_in,
   const std::complex<T> *data_in, std::complex<T> *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape)==0) return;
   util::sanity_check(shape, stride_in, stride_out, data_in==data_out, axes);
   ndarr<cmplx<T>> ain(data_in, shape, stride_in),
                   aout(data_out, shape, stride_out);
@@ -2420,9 +2449,12 @@ template<typename T> void r2c(const shape_t &shape_in,
   const T *data_in, std::complex<T> *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape_in)==0) return;
   util::sanity_check(shape_in, stride_in, stride_out, false, axis);
   ndarr<T> ain(data_in, shape_in, stride_in);
-  ndarr<cmplx<T>> aout(data_out, shape_in, stride_out); // FIXME
+  shape_t shape_out(shape_in);
+  shape_out[axis] = shape_in[axis]/2 + 1;
+  ndarr<cmplx<T>> aout(data_out, shape_out, stride_out);
   general_r2c(ain, aout, axis, fct);
   }
 
@@ -2431,6 +2463,7 @@ template<typename T> void r2c(const shape_t &shape_in,
   const T *data_in, std::complex<T> *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape_in)==0) return;
   util::sanity_check(shape_in, stride_in, stride_out, false, axes);
   r2c(shape_in, stride_in, stride_out, axes.back(), data_in, data_out, fct);
   if (axes.size()==1) return;
@@ -2447,6 +2480,7 @@ template<typename T> void c2r(const shape_t &shape_out,
   const std::complex<T> *data_in, T *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape_out)==0) return;
   util::sanity_check(shape_out, stride_in, stride_out, false, axis);
   shape_t shape_in(shape_out);
   shape_in[axis] = shape_out[axis]/2 + 1;
@@ -2460,6 +2494,7 @@ template<typename T> void c2r(const shape_t &shape_out,
   const std::complex<T> *data_in, T *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape_out)==0) return;
   if (axes.size()==1)
     {
     c2r(shape_out, stride_in, stride_out, axes[0], data_in, data_out, fct);
@@ -2486,6 +2521,7 @@ template<typename T> void r2r_fftpack(const shape_t &shape,
   bool forward, const T *data_in, T *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape)==0) return;
   util::sanity_check(shape, stride_in, stride_out, data_in==data_out, axis);
   ndarr<T> ain(data_in, shape, stride_in), aout(data_out, shape, stride_out);
   general_r(ain, aout, axis, forward, fct);
@@ -2496,6 +2532,7 @@ template<typename T> void r2r_hartley(const shape_t &shape,
   const T *data_in, T *data_out, T fct)
   {
   using namespace detail;
+  if (util::prod(shape)==0) return;
   util::sanity_check(shape, stride_in, stride_out, data_in==data_out, axes);
   ndarr<T> ain(data_in, shape, stride_in), aout(data_out, shape, stride_out);
   general_hartley(ain, aout, axes, fct);