Merge pull request #23031 from charris/backport-23016

BUG: use `_Alignof` rather than `offsetof()` on most compilers
numpy · Jan 18, 2023 · e8f62ea · e8f62ea
2 parents 104df7c + b3760fe
commit e8f62ea
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Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/numpy/core/src/multiarray/arraytypes.c.src b/numpy/core/src/multiarray/arraytypes.c.src
@@ -224,8 +224,6 @@ MyPyLong_AsUnsigned@Type@(PyObject *obj)
  **                         GETITEM AND SETITEM                             **
  *****************************************************************************
  */
-
-#define _ALIGN(type) offsetof(struct {char c; type v;}, v)
 /*
  * Disable harmless compiler warning "4116: unnamed type definition in
  * parentheses" which is caused by the _ALIGN macro.

diff --git a/numpy/core/src/multiarray/common.h b/numpy/core/src/multiarray/common.h
@@ -178,7 +178,19 @@ check_and_adjust_axis(int *axis, int ndim)
 }
 
 /* used for some alignment checks */
-#define _ALIGN(type) offsetof(struct {char c; type v;}, v)
+/* 
+ * GCC releases before GCC 4.9 had a bug in _Alignof.  See GCC bug 52023
+ * <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>.
+ * clang versions < 8.0.0 have the same bug.
+ */
+#if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \
+     || (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \
+  && !defined __clang__) \
+     || (defined __clang__ && __clang_major__ < 8))
+# define _ALIGN(type) offsetof(struct {char c; type v;}, v)
+#else
+# define _ALIGN(type) _Alignof(type)
+#endif
 #define _UINT_ALIGN(type) npy_uint_alignment(sizeof(type))
 /*
  * Disable harmless compiler warning "4116: unnamed type definition in