fix buffer format validation for sequences of strings in structs

CHANGES.rst

@@ -18,6 +18,8 @@ Bugs fixed
 
 * C++ destructor calls in extension types could fail to compile in clang.
 
+* Buffer format validation failed for sequences of strings in structs.
+
 * Docstrings on extension type attributes in .pxd files were rejected.
 
 

Cython/Utility/Buffer.c

@@ -638,8 +638,8 @@ static const char* __Pyx_BufFmt_CheckString(__Pyx_BufFmt_Context* ctx, const cha
   int got_Z = 0;
 
   while (1) {
-    switch(*ts) {
     /* puts(ts); */
+    switch(*ts) {
       case 0:
         if (ctx->enc_type != 0 && ctx->head == NULL) {
           __Pyx_BufFmt_RaiseExpected(ctx);
@@ -730,23 +730,29 @@ static const char* __Pyx_BufFmt_CheckString(__Pyx_BufFmt_Context* ctx, const cha
         if (*ts != 'f' && *ts != 'd' && *ts != 'g') {
           __Pyx_BufFmt_RaiseUnexpectedChar('Z');
           return NULL;
-        }        /* fall through */
+        }
+        /* fall through */
       case 'c': case 'b': case 'B': case 'h': case 'H': case 'i': case 'I':
       case 'l': case 'L': case 'q': case 'Q':
       case 'f': case 'd': case 'g':
-      case 'O': case 's': case 'p':
+      case 'O': case 'p':
         if (ctx->enc_type == *ts && got_Z == ctx->is_complex &&
             ctx->enc_packmode == ctx->new_packmode) {
           /* Continue pooling same type */
           ctx->enc_count += ctx->new_count;
-        } else {
-          /* New type */
+          ctx->new_count = 1;
+          got_Z = 0;
+          ++ts;
+          break;
+        }
+        /* fall through */
+      case 's':
+        /* 's' or new type (cannot be added to current pool) */
         if (__Pyx_BufFmt_ProcessTypeChunk(ctx) == -1) return NULL;
         ctx->enc_count = ctx->new_count;
         ctx->enc_packmode = ctx->new_packmode;
         ctx->enc_type = *ts;
         ctx->is_complex = got_Z;
-        }
         ++ts;
         ctx->new_count = 1;
         got_Z = 0;

tests/buffers/buffmt.pyx

@@ -377,6 +377,22 @@ def partially_packed_struct_2(fmt):
         fmt, sizeof(PartiallyPackedStruct2))
 
 
+cdef packed struct PackedStructWithCharArrays:
+    float a
+    int b
+    char[5] c
+    char[3] d
+
+
+@testcase
+def packed_struct_with_strings(fmt):
+    """
+    >>> packed_struct_with_strings("T{f:a:i:b:5s:c:3s:d:}")
+    """
+    cdef object[PackedStructWithCharArrays] buf = MockBuffer(
+        fmt, sizeof(PackedStructWithCharArrays))
+
+
 # TODO: empty struct
 # TODO: Incomplete structs
 # TODO: mixed structs