Support partial unions in a way very similar to partial structs.

Needed for a python-cffi mail.

5 files changed, 40 insertions, 15 deletions

diff --git a/cffi/cparser.py b/cffi/cparser.py
index 6c248b3..1048934 100644
--- a/cffi/cparser.py
+++ b/cffi/cparser.py
@@ -488,7 +488,7 @@ class Parser(object):
         return tp
 
     def _make_partial(self, tp, nested):
-        if not isinstance(tp, model.StructType):
+        if not isinstance(tp, model.StructOrUnion):
             raise api.CDefError("%s cannot be partial" % (tp,))
         if not tp.has_c_name() and not nested:
             raise NotImplementedError("%s is partial but has no C name" %(tp,))
diff --git a/cffi/model.py b/cffi/model.py
index 2a9373f..2e989b3 100644
--- a/cffi/model.py
+++ b/cffi/model.py
@@ -248,6 +248,7 @@ class StructOrUnionOrEnum(BaseTypeByIdentity):
 class StructOrUnion(StructOrUnionOrEnum):
     fixedlayout = None
     completed = False
+    partial = False
 
     def __init__(self, name, fldnames, fldtypes, fldbitsize):
         self.name = name
@@ -344,11 +345,6 @@ class StructOrUnion(StructOrUnionOrEnum):
         from .ffiplatform import VerificationError
         raise VerificationError(msg)
 
-
-class StructType(StructOrUnion):
-    kind = 'struct'
-    partial = False
-
     def check_not_partial(self):
         if self.partial and self.fixedlayout is None:
             from . import ffiplatform
@@ -357,19 +353,18 @@ class StructType(StructOrUnion):
     def build_backend_type(self, ffi, finishlist):
         self.check_not_partial()
         finishlist.append(self)
-        
-        return global_cache(self, ffi, 'new_struct_type',
+        #
+        return global_cache(self, ffi, 'new_%s_type' % self.kind,
                             self.get_official_name(), key=self)
 
 
+class StructType(StructOrUnion):
+    kind = 'struct'
+
+
 class UnionType(StructOrUnion):
     kind = 'union'
 
-    def build_backend_type(self, ffi, finishlist):
-        finishlist.append(self)
-        return global_cache(self, ffi, 'new_union_type',
-                            self.get_official_name(), key=self)
-
 
 class EnumType(StructOrUnionOrEnum):
     kind = 'enum'
diff --git a/cffi/vengine_cpy.py b/cffi/vengine_cpy.py
index e8f3575..bcd0e06 100644
--- a/cffi/vengine_cpy.py
+++ b/cffi/vengine_cpy.py
@@ -491,7 +491,7 @@ class VCPythonEngine(object):
         #
         function = getattr(module, layoutfuncname)
         layout = function()
-        if isinstance(tp, model.StructType) and tp.partial:
+        if isinstance(tp, model.StructOrUnion) and tp.partial:
             # use the function()'s sizes and offsets to guide the
             # layout of the struct
             totalsize = layout[0]
diff --git a/cffi/vengine_gen.py b/cffi/vengine_gen.py
index dc38bb7..24cce71 100644
--- a/cffi/vengine_gen.py
+++ b/cffi/vengine_gen.py
@@ -282,7 +282,7 @@ class VGenericEngine(object):
             if x < 0: break
             layout.append(x)
             num += 1
-        if isinstance(tp, model.StructType) and tp.partial:
+        if isinstance(tp, model.StructOrUnion) and tp.partial:
             # use the function()'s sizes and offsets to guide the
             # layout of the struct
             totalsize = layout[0]
diff --git a/testing/test_verify.py b/testing/test_verify.py
index b88e4e8..e98c128 100644
--- a/testing/test_verify.py
+++ b/testing/test_verify.py
@@ -1162,6 +1162,36 @@ def test_ffi_union():
     ffi.cdef("union foo_u { char x; long *z; };")
     ffi.verify("union foo_u { char x; int y; long *z; };")
 
+def test_ffi_union_partial():
+    ffi = FFI()
+    ffi.cdef("union foo_u { char x; ...; };")
+    ffi.verify("union foo_u { char x; int y; };")
+    assert ffi.sizeof("union foo_u") == 4
+
+def test_ffi_union_with_partial_struct():
+    ffi = FFI()
+    ffi.cdef("struct foo_s { int x; ...; }; union foo_u { struct foo_s s; };")
+    ffi.verify("struct foo_s { int a; int x; }; "
+               "union foo_u { char b[32]; struct foo_s s; };")
+    assert ffi.sizeof("struct foo_s") == 8
+    assert ffi.sizeof("union foo_u") == 32
+
+def test_ffi_union_partial_2():
+    ffi = FFI()
+    ffi.cdef("typedef union { char x; ...; } u1;")
+    ffi.verify("typedef union { char x; int y; } u1;")
+    assert ffi.sizeof("u1") == 4
+
+def test_ffi_union_with_partial_struct_2():
+    ffi = FFI()
+    ffi.cdef("typedef struct { int x; ...; } s1;"
+             "typedef union { s1 s; } u1;")
+    ffi.verify("typedef struct { int a; int x; } s1; "
+               "typedef union { char b[32]; s1 s; } u1;")
+    assert ffi.sizeof("s1") == 8
+    assert ffi.sizeof("u1") == 32
+    assert ffi.offsetof("u1", "s") == 0
+
 def test_ffi_struct_packed():
     if sys.platform == 'win32':
         py.test.skip("needs a GCC extension")