ARROW-10193: [Python] Segfault when converting to fixed size binary array

cpp/src/arrow/array/builder_binary.h

@@ -447,6 +447,10 @@ class ARROW_EXPORT FixedSizeBinaryBuilder : public ArrayBuilder {
     }
   }
 
+  void UnsafeAppend(const char* value) {
+    UnsafeAppend(reinterpret_cast<const uint8_t*>(value));
+  }
+
   void UnsafeAppend(util::string_view value) {
 #ifndef NDEBUG
     CheckValueSize(static_cast<size_t>(value.size()));

cpp/src/arrow/python/python_to_arrow.cc

@@ -1034,7 +1034,7 @@ Result<std::shared_ptr<ChunkedArray>> ConvertPySequence(PyObject* obj, PyObject*
     return chunked_converter->ToChunkedArray();
   } else {
     // If the converter can't overflow spare the capacity error checking on the hot-path,
-    // this improves the performance roughly by ~10 for primitive types.
+    // this improves the performance roughly by ~10% for primitive types.
     if (mask != nullptr && mask != Py_None) {
       RETURN_NOT_OK(ExtendMasked(converter.get(), seq, mask, size));
     } else {

python/pyarrow/tests/test_convert_builtin.py

@@ -764,6 +764,15 @@ def test_fixed_size_bytes_does_not_accept_varying_lengths():
         pa.array(data, type=pa.binary(4))
 
 
+def test_fixed_size_binary_length_check():
+    # ARROW-10193
+    data = [b'\x19h\r\x9e\x00\x00\x00\x00\x01\x9b\x9fA']
+    assert len(data[0]) == 12
+    ty = pa.binary(12)
+    arr = pa.array(data, type=ty)
+    assert arr.to_pylist() == data
+
+
 def test_sequence_date():
     data = [datetime.date(2000, 1, 1), None, datetime.date(1970, 1, 1),
             datetime.date(2040, 2, 26)]