Workaround for numpy/numpy#9049

This moves the ^ in the format string (to specify unaligned) to outside the `T{}` where it is sure to be parsed correctly. This is not strictly necessary yet, but it paves the way for pybind#832.
bmerry · May 4, 2017 · 271f380 · 271f380
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commit 271f380
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Showing 2 changed files with 16 additions and 15 deletions.
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
@@ -991,14 +991,15 @@ inline PYBIND11_NOINLINE void register_structured_dtype(
         [](const field_descriptor &a, const field_descriptor &b) { return a.offset < b.offset; });
     size_t offset = 0;
     std::ostringstream oss;
-    oss << "T{";
+    // mark the structure as unaligned with '^', because numpy and C++ don't
+    // always agree about alignment (particularly for complex), and we're
+    // explicitly listing all our padding. This depends on none of the fields
+    // overriding the endianness. Putting the ^ in front of individual fields
+    // isn't guaranteed to work due to https://github.com/numpy/numpy/issues/9049
+    oss << "^T{";
     for (auto& field : ordered_fields) {
         if (field.offset > offset)
             oss << (field.offset - offset) << 'x';
-        // mark all fields with '^' (unaligned native type), because numpy
-        // and C++ don't always agree about alignment (particularly for
-        // complex, and we're explicitly listing all padding.
-        oss << '^';
         oss << field.format << ':' << field.name << ':';
         offset = field.offset + field.size;
     }

diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
@@ -72,22 +72,22 @@ def test_format_descriptors():
     assert re.match('^NumPy type info missing for .*UnboundStruct.*$', str(excinfo.value))
 
     ld = np.dtype('longdouble')
-    ldbl_fmt = ('4x' if ld.alignment > 4 else '') + '^' + ld.char
-    ss_fmt = "T{^?:bool_:3x^I:uint_:^f:float_:" + ldbl_fmt + ":ldbl_:}"
+    ldbl_fmt = ('4x' if ld.alignment > 4 else '') + ld.char
+    ss_fmt = "^T{?:bool_:3xI:uint_:f:float_:" + ldbl_fmt + ":ldbl_:}"
     dbl = np.dtype('double')
-    partial_fmt = ("T{^?:bool_:3x^I:uint_:^f:float_:" +
+    partial_fmt = ("^T{?:bool_:3xI:uint_:f:float_:" +
                    str(4 * (dbl.alignment > 4) + dbl.itemsize + 8 * (ld.alignment > 8)) +
-                   "x^g:ldbl_:}")
+                   "xg:ldbl_:}")
     nested_extra = str(max(8, ld.alignment))
     assert print_format_descriptors() == [
         ss_fmt,
-        "T{^?:bool_:^I:uint_:^f:float_:^g:ldbl_:}",
-        "T{^" + ss_fmt + ":a:^T{^?:bool_:^I:uint_:^f:float_:^g:ldbl_:}:b:}",
+        "^T{?:bool_:I:uint_:f:float_:g:ldbl_:}",
+        "^T{" + ss_fmt + ":a:^T{?:bool_:I:uint_:f:float_:g:ldbl_:}:b:}",
         partial_fmt,
-        "T{" + nested_extra + "x^" + partial_fmt + ":a:" + nested_extra + "x}",
-        "T{^3s:a:^3s:b:}",
-        'T{^q:e1:^B:e2:}',
-        'T{^Zf:cflt:^Zd:cdbl:}'
+        "^T{" + nested_extra + "x" + partial_fmt + ":a:" + nested_extra + "x}",
+        "^T{3s:a:3s:b:}",
+        '^T{q:e1:B:e2:}',
+        '^T{Zf:cflt:Zd:cdbl:}'
     ]