BUG: Fix NPY_* macros for endianness (#1154).

I managed to screw them up: they did not actually mimic the gblic
endian.h behavior, that is NPY_BIG_ENDIAN and NPY_LITTLE_ENDIAN should
always be defined, and endianness should be detected by comparison with
NPY_BYTE_ORDER. This needs to be fixed because the behavior of the NPY_
macros was different depending on whether endian.h was available or not.
Let's hope nobody depended on it...

(cherry picked from commit 1eee475d3429832bfaf4022ab24c9a50b97e123a)

4 files changed, 13 insertions, 16 deletions

diff --git a/doc/source/reference/c-api.config.rst b/doc/source/reference/c-api.config.rst
index 0c7f6b147..0989c53d7 100644
--- a/doc/source/reference/c-api.config.rst
+++ b/doc/source/reference/c-api.config.rst
@@ -89,8 +89,8 @@ Platform information
     .. versionadded:: 1.3.0
 
     Portable alternatives to the ``endian.h`` macros of GNU Libc.
-    One of :cdata:`NPY_BIG_ENDIAN` :cdata:`NPY_LITTLE_ENDIAN` or
-    is defined, and :cdata:`NPY_BYTE_ORDER` is either 4321 or 1234.
+    If big endian, :cdata:`NPY_BYTE_ORDER` == :cdata:`NPY_BIG_ENDIAN`, and
+    similarly for little endian architectures.
 
     Defined in ``numpy/npy_endian.h``.
 
diff --git a/numpy/core/code_generators/generate_numpy_api.py b/numpy/core/code_generators/generate_numpy_api.py
index 4dda84146..96a19d94f 100644
--- a/numpy/core/code_generators/generate_numpy_api.py
+++ b/numpy/core/code_generators/generate_numpy_api.py
@@ -94,13 +94,13 @@ _import_array(void)
     PyErr_Format(PyExc_RuntimeError, "FATAL: module compiled as unknown endian");
     return -1;
   }
-#ifdef NPY_BIG_ENDIAN
+#if NPY_BYTE_ORDER ==NPY_BIG_ENDIAN
   if (st != NPY_CPU_BIG) {
     PyErr_Format(PyExc_RuntimeError, "FATAL: module compiled as "\
         "big endian, but detected different endianness at runtime");
     return -1;
   }
-#elif defined(NPY_LITTLE_ENDIAN)
+#elif NPY_BYTE_ORDER == NPY_LITTLE_ENDIAN
   if (st != NPY_CPU_LITTLE) {
     PyErr_Format(PyExc_RuntimeError, "FATAL: module compiled as"\
         "little endian, but detected different endianness at runtime");
diff --git a/numpy/core/include/numpy/ndarrayobject.h b/numpy/core/include/numpy/ndarrayobject.h
index d23aa0120..8c38acdd4 100644
--- a/numpy/core/include/numpy/ndarrayobject.h
+++ b/numpy/core/include/numpy/ndarrayobject.h
@@ -1038,7 +1038,7 @@ typedef struct {
 #define NPY_SWAP 's'
 #define NPY_IGNORE '|'
 
-#ifdef NPY_BIG_ENDIAN
+#if NPY_BYTE_ORDER == NPY_BIG_ENDIAN
 #define NPY_NATBYTE NPY_BIG
 #define NPY_OPPBYTE NPY_LITTLE
 #else
diff --git a/numpy/core/include/numpy/npy_endian.h b/numpy/core/include/numpy/npy_endian.h
index 0a5c05ef9..e0d534c86 100644
--- a/numpy/core/include/numpy/npy_endian.h
+++ b/numpy/core/include/numpy/npy_endian.h
@@ -9,26 +9,23 @@
 #ifdef NPY_HAVE_ENDIAN_H
     /* Use endian.h if available */
     #include <endian.h>
+
     #define NPY_BYTE_ORDER __BYTE_ORDER
-    #if (__BYTE_ORDER == __LITTLE_ENDIAN)
-        #define NPY_LITTLE_ENDIAN
-    #elif (__BYTE_ORDER == __BIG_ENDIAN)
-        #define NPY_BIG_ENDIAN
-    #else
-        #error Unknown machine endianness detected.
-    #endif
+    #define NPY_LITTLE_ENDIAN __LITTLE_ENDIAN
+    #define NPY_BIG_ENDIAN __BIG_ENDIAN
 #else
     /* Set endianness info using target CPU */
     #include "npy_cpu.h"
 
+    #define NPY_LITTLE_ENDIAN 1234
+    #define NPY_BIG_ENDIAN 4321
+
     #if defined(NPY_CPU_X86) || defined(NPY_CPU_AMD64)\
             || defined(NPY_CPU_IA64)
-        #define NPY_LITTLE_ENDIAN
-        #define NPY_BYTE_ORDER 1234
+        #define NPY_BYTE_ORDER NPY_LITTLE_ENDIAN
     #elif defined(NPY_CPU_PPC) || defined(NPY_CPU_SPARC)\
             || defined(NPY_CPU_S390) || defined(NPY_CPU_PARISC) || defined(NPY_CPU_PPC64)
-        #define NPY_BIG_ENDIAN
-        #define NPY_BYTE_ORDER 4321
+        #define NPY_BYTE_ORDER NPY_BIG_ENDIAN
     #else
         #error Unknown CPU: can not set endianness
     #endif