Added validation checks on memoryviews.

Cython/Compiler/MemoryView.py

@@ -106,8 +106,51 @@ def get_axes_specs(env, axes):
         else:
             raise CompileError(axis.step.pos, INVALID_ERR)
 
+
+    validate_axes_specs(axes[0].start.pos, axes_specs)
+
     return axes_specs
 
+def validate_axes_specs(pos, specs):
+
+    packing_specs = ('contig', 'strided', 'follow')
+    access_specs = ('direct', 'ptr', 'full')
+
+    is_c_contig = is_f_contig = False
+
+    packing_idx = 1
+
+    if (specs[0][packing_idx] == 'contig' and 
+        all(axis[packing_idx] == 'follow' for axis in specs[1:])):
+        # f_contiguous: 'contig', 'follow', 'follow', ..., 'follow'
+        is_f_contig = True
+
+    elif (len(specs) > 1 and 
+          specs[-1][packing_idx] == 'contig' and 
+          all(axis[packing_idx] == 'follow' for axis in specs[:-1])):
+        # c_contiguous: 'follow', 'follow', ..., 'follow', 'contig'
+        is_c_contig = True
+    
+    has_contig = has_follow = has_strided = False
+
+    for access, packing in specs:
+
+        if not (access in access_specs and
+                packing in packing_specs):
+            raise CompileError(pos, "Invalid axes specification.")
+
+        if packing == 'strided':
+            has_strided = True
+        elif packing == 'contig':
+            if has_contig:
+                raise CompileError(pos, "Only one contiguous axis may be specified.")
+            has_contig = True
+        elif packing == 'follow':
+            if has_strided:
+                raise CompileError(pos, "A memoryview cannot have both follow and strided axis specifiers.")
+            if not (is_c_contig or is_f_contig):
+                raise CompileError(pos, "Invalid use of the follow specifier.")
+
 
 def _get_resolved_spec(env, spec):
     # spec must be a NameNode or an AttributeNode

Cython/Compiler/PyrexTypes.py

@@ -311,6 +311,40 @@ class CTypedefType(BaseType):
 class MemoryViewType(BaseType):
 
     def __init__(self, base, axes):
+        '''
+        MemoryViewType(base, axes)
+
+        Base is the C base type; axes is a list of (access, packing) strings,
+        where access is one of 'full', 'direct' or 'ptr' and packing is one of
+        'contig', 'strided' or 'follow'.  There is one (access, packing) tuple
+        for each dimension.
+
+        the access specifiers determine whether the array data contains
+        pointers that need to be dereferenced along that axis when
+        retrieving/setting:
+
+        'direct' -- No pointers stored in this dimension.
+        'ptr' -- Pointer stored in this dimension.
+        'full' -- Check along this dimension, don't assume either.
+
+        the packing specifiers specify how the array elements are layed-out
+        in memory.
+
+        'contig' -- The data are contiguous in memory along this dimension.
+                At most one dimension may be specified as 'contig'.
+        'strided' -- The data aren't contiguous along this dimenison.
+        'follow' -- Used for C/Fortran contiguous arrays, a 'follow' dimension
+            has its stride automatically computed from extents of the other
+            dimensions to ensure C or Fortran memory layout.
+
+        C-contiguous memory has 'direct' as the access spec, 'contig' as the
+        *last* axis' packing spec and 'follow' for all other packing specs.
+
+        Fortran-contiguous memory has 'direct' as the access spec, 'contig' as
+        the *first* axis' packing spec and 'follow' for all other packing
+        specs.
+        '''
+
         self.base = base
         self.axes = axes
 

tests/compile/memview_declaration.pyx

@@ -14,4 +14,4 @@ cdef unsigned long[0:, 0:, 0:, 0::0x0001] c_contig0
 
 cdef float[::foo & bar, ::cython.view.direct & cython.view.follow] view4
 cdef int[::view.full & foo] view3
-cdef int[::view.ptr & follow] view1000
+cdef int[::view.ptr & view.strided] view1000

tests/errors/memview_declarations.pyx

+# mode: error
+
 cimport cython
 from cython.view cimport contig as foo, full as bar, follow
 from cython cimport view
-
 biz = cython.view.contig
 foz = cython.view.full
-
 adict = {'view': cython.view}
 alist = [adict]
 
@@ -24,6 +24,7 @@ cdef signed char[::view.ptr & view.direct] no_access_spec
 cdef signed char[::1-1+1] expr_spec
 cdef signed char[::blargh] bad_name
 cdef double[::alist[0]['view'].full] expr_attribute
+cdef double[::view.ptr & view.follow] no_single_follow
 
 _ERRORS = u'''
 11:25: Cannot specify an array that is both C and Fortran contiguous.
@@ -42,4 +43,5 @@ _ERRORS = u'''
 24:22: Invalid axis specification.
 25:25: Invalid axis specification.
 26:22: no expressions allowed in axis spec, only names (e.g. cython.view.contig).
+27:12: Invalid use of the follow specifier.
 '''