bpo-11410: Standardize and use symbol visibility attributes across POSIX and Windows. (GH-16347)

2 files changed, 43 insertions, 11 deletions

diff --git a/Include/exports.h b/Include/exports.h
new file mode 100644
index 0000000..fc1a5c5
--- /dev/null
+++ b/Include/exports.h
@@ -0,0 +1,30 @@
+#ifndef Py_EXPORTS_H
+#define Py_EXPORTS_H
+
+#if defined(_WIN32) || defined(__CYGWIN__)
+    #define Py_IMPORTED_SYMBOL __declspec(dllimport)
+    #define Py_EXPORTED_SYMBOL __declspec(dllexport)
+    #define Py_LOCAL_SYMBOL
+#else
+/*
+ * If we only ever used gcc >= 5, we could use __has_attribute(visibility)
+ * as a cross-platform way to determine if visibility is supported. However,
+ * we may still need to support gcc >= 4, as some Ubuntu LTS and Centos versions
+ * have 4 < gcc < 5.
+ */
+    #ifndef __has_attribute
+      #define __has_attribute(x) 0  // Compatibility with non-clang compilers.
+    #endif
+    #if (defined(__GNUC__) && (__GNUC__ >= 4)) ||\
+        (defined(__clang__) && __has_attribute(visibility))
+        #define Py_IMPORTED_SYMBOL __attribute__ ((visibility ("default")))
+        #define Py_EXPORTED_SYMBOL __attribute__ ((visibility ("default")))
+        #define Py_LOCAL_SYMBOL  __attribute__ ((visibility ("hidden")))
+    #else
+        #define Py_IMPORTED_SYMBOL
+        #define Py_EXPORTED_SYMBOL
+        #define Py_LOCAL_SYMBOL
+    #endif
+#endif
+
+#endif /* Py_EXPORTS_H */
diff --git a/Include/pyport.h b/Include/pyport.h
index 51967d1..64c73f0 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -638,16 +638,18 @@ extern char * _getpty(int *, int, mode_t, int);
 #       define HAVE_DECLSPEC_DLL
 #endif
 
+#include "exports.h"
+
 /* only get special linkage if built as shared or platform is Cygwin */
 #if defined(Py_ENABLE_SHARED) || defined(__CYGWIN__)
 #       if defined(HAVE_DECLSPEC_DLL)
 #               if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
-#                       define PyAPI_FUNC(RTYPE) __declspec(dllexport) RTYPE
-#                       define PyAPI_DATA(RTYPE) extern __declspec(dllexport) RTYPE
+#                       define PyAPI_FUNC(RTYPE) Py_EXPORTED_SYMBOL RTYPE
+#                       define PyAPI_DATA(RTYPE) extern Py_EXPORTED_SYMBOL RTYPE
         /* module init functions inside the core need no external linkage */
         /* except for Cygwin to handle embedding */
 #                       if defined(__CYGWIN__)
-#                               define PyMODINIT_FUNC __declspec(dllexport) PyObject*
+#                               define PyMODINIT_FUNC Py_EXPORTED_SYMBOL PyObject*
 #                       else /* __CYGWIN__ */
 #                               define PyMODINIT_FUNC PyObject*
 #                       endif /* __CYGWIN__ */
@@ -658,14 +660,14 @@ extern char * _getpty(int *, int, mode_t, int);
         /* failures similar to those described at the bottom of 4.1: */
         /* http://docs.python.org/extending/windows.html#a-cookbook-approach */
 #                       if !defined(__CYGWIN__)
-#                               define PyAPI_FUNC(RTYPE) __declspec(dllimport) RTYPE
+#                               define PyAPI_FUNC(RTYPE) Py_IMPORTED_SYMBOL RTYPE
 #                       endif /* !__CYGWIN__ */
-#                       define PyAPI_DATA(RTYPE) extern __declspec(dllimport) RTYPE
+#                       define PyAPI_DATA(RTYPE) extern Py_IMPORTED_SYMBOL RTYPE
         /* module init functions outside the core must be exported */
 #                       if defined(__cplusplus)
-#                               define PyMODINIT_FUNC extern "C" __declspec(dllexport) PyObject*
+#                               define PyMODINIT_FUNC extern "C" Py_EXPORTED_SYMBOL PyObject*
 #                       else /* __cplusplus */
-#                               define PyMODINIT_FUNC __declspec(dllexport) PyObject*
+#                               define PyMODINIT_FUNC Py_EXPORTED_SYMBOL PyObject*
 #                       endif /* __cplusplus */
 #               endif /* Py_BUILD_CORE */
 #       endif /* HAVE_DECLSPEC_DLL */
@@ -673,16 +675,16 @@ extern char * _getpty(int *, int, mode_t, int);
 
 /* If no external linkage macros defined by now, create defaults */
 #ifndef PyAPI_FUNC
-#       define PyAPI_FUNC(RTYPE) RTYPE
+#       define PyAPI_FUNC(RTYPE) Py_EXPORTED_SYMBOL RTYPE
 #endif
 #ifndef PyAPI_DATA
-#       define PyAPI_DATA(RTYPE) extern RTYPE
+#       define PyAPI_DATA(RTYPE) extern Py_EXPORTED_SYMBOL RTYPE
 #endif
 #ifndef PyMODINIT_FUNC
 #       if defined(__cplusplus)
-#               define PyMODINIT_FUNC extern "C" PyObject*
+#               define PyMODINIT_FUNC extern "C" Py_EXPORTED_SYMBOL PyObject*
 #       else /* __cplusplus */
-#               define PyMODINIT_FUNC PyObject*
+#               define PyMODINIT_FUNC Py_EXPORTED_SYMBOL PyObject*
 #       endif /* __cplusplus */
 #endif