Align on first member of nested struct if first member in struct

Cython/Utility/Buffer.c

@@ -489,6 +489,7 @@ __pyx_buffmt_parse_array(__Pyx_BufFmt_Context* ctx, const char** tsp)
 
 static const char* __Pyx_BufFmt_CheckString(__Pyx_BufFmt_Context* ctx, const char* ts) {
   int got_Z = 0;
+
   while (1) {
     switch(*ts) {
       case 0:
@@ -533,20 +534,24 @@ static const char* __Pyx_BufFmt_CheckString(__Pyx_BufFmt_Context* ctx, const cha
         {
           const char* ts_after_sub;
           size_t i, struct_count = ctx->new_count;
+          size_t struct_alignment = ctx->struct_alignment;
           ctx->new_count = 1;
           ++ts;
           if (*ts != '{') {
             PyErr_SetString(PyExc_ValueError, "Buffer acquisition: Expected '{' after 'T'");
             return NULL;
           }
+          if (__Pyx_BufFmt_ProcessTypeChunk(ctx) == -1) return NULL;
+          ctx->enc_type = 0; /* Erase processed last struct element */
+          ctx->struct_alignment = 0;
           ++ts;
           ts_after_sub = ts;
-          ctx->struct_alignment = 0;
           for (i = 0; i != struct_count; ++i) {
             ts_after_sub = __Pyx_BufFmt_CheckString(ctx, ts);
             if (!ts_after_sub) return NULL;
           }
           ts = ts_after_sub;
+          if (struct_alignment) ctx->struct_alignment = struct_alignment;
         }
         break;
       case '}': /* end of substruct; either repeat or move on */

tests/run/memslice.pyx

@@ -1538,11 +1538,37 @@ cdef struct AlignedNestedNormal:
     PaddedAtEndNormal a
     char chars
 
+# Test nested structs in a struct, make sure we compute padding each time
+# accordingly. If the first struct member is a struct, align on the first
+# member of that struct (recursively)
+cdef struct A:
+    double d
+    char c
+
+cdef struct B:
+    char c1
+    A a
+    char c2
+
+cdef struct C:
+    A a
+    char c1
+
+cdef struct D:
+    B b
+    C cstruct
+    int a[2]
+    char c
+
 cdef fused FusedPadded:
     ArrayStruct
     PackedArrayStruct
     AlignedNested
     AlignedNestedNormal
+    A
+    B
+    C
+    D
 
 @testcase
 def test_padded_structs():