MAINT: improve thread-local storage usage in ccallback.h

The old code only worked for GCC and MSVC; Clang would fall
back to using `PyThread_State` rather than using `_Thread_local`.
This should be faster, and also cleans up some duplicated code.

Introducing a dedicated dependency `ccallback_dep` makes clearer
why some build targets in other modules were adding `../_lib/src` to
their include directories.

Author: rgommers

scipy/_lib/meson.build

@@ -31,18 +31,20 @@ lib_cython_gen = generator(cython,
   output : '@[email protected]',
   depends : [_cython_tree, _lib_pxd])
 
+ccallback_dep = declare_dependency(include_directories: ['..', 'src'])
+
 py3.extension_module('_ccallback_c',
   lib_cython_gen.process('_ccallback_c.pyx'),
   c_args: [cython_c_args, Wno_discarded_qualifiers],
-  include_directories: 'src',
+  dependencies: ccallback_dep,
   link_args: version_link_args,
   install: true,
   subdir: 'scipy/_lib'
 )
 
 py3.extension_module('_test_ccallback',
   'src/_test_ccallback.c',
-  include_directories: 'src',
+  dependencies: ccallback_dep,
   link_args: version_link_args,
   install: true,
   subdir: 'scipy/_lib',

scipy/_lib/src/ccallback.h

@@ -22,6 +22,8 @@
 #include <Python.h>
 #include <setjmp.h>
 
+#include "scipy_config.h"
+
 /* Default behavior */
 #define CCALLBACK_DEFAULTS 0x0
 /* Whether calling ccallback_obtain is enabled */
@@ -66,32 +68,9 @@ struct ccallback {
  * Thread-local storage
  */
 
-#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && (__GNUC_MINOR__ >= 4)))
-
-static __thread ccallback_t *_active_ccallback = NULL;
-
-static void *ccallback__get_thread_local(void)
-{
-    return (void *)_active_ccallback;
-}
-
-static int ccallback__set_thread_local(void *value)
-{
-    _active_ccallback = value;
-    return 0;
-}
-
-/*
- * Obtain a pointer to the current ccallback_t structure.
- */
-static ccallback_t *ccallback_obtain(void)
-{
-    return (ccallback_t *)ccallback__get_thread_local();
-}
-
-#elif defined(_MSC_VER)
+#if !defined(SCIPY_TLS_EMPTY)
 
-static __declspec(thread) ccallback_t *_active_ccallback = NULL;
+static SCIPY_TLS ccallback_t *_active_ccallback = NULL;
 
 static void *ccallback__get_thread_local(void)
 {

scipy/integrate/meson.build

@@ -63,8 +63,7 @@ dop_lib = static_library('dop_lib',
 
 py3.extension_module('_quadpack',
   ['__quadpack.h', '__quadpack.c'],
-  include_directories: ['../_lib/src'],
-  dependencies: np_dep,
+  dependencies: [np_dep, ccallback_dep],
   install: true,
   subdir: 'scipy/integrate'
 )

scipy/ndimage/meson.build

@@ -9,8 +9,8 @@ py3.extension_module('_nd_image',
     'src/ni_splines.c',
     'src/ni_support.c'
   ],
-  include_directories: ['../_lib/src', '../_build_utils/src'],
-  dependencies: np_dep,
+  include_directories: ['../_build_utils/src'],
+  dependencies: [np_dep, ccallback_dep],
   link_args: version_link_args,
   install: true,
   subdir: 'scipy/ndimage'

scipy/optimize/meson.build

@@ -19,8 +19,7 @@ py3.extension_module('_minpack',
     '__minpack.h',
     '__minpack.c',
   ],
-  include_directories: '../_lib/src',
-  dependencies: np_dep,
+  dependencies: [np_dep, ccallback_dep],
   install: true,
   subdir: 'scipy/optimize'
 )

scipy/stats/_unuran/meson.build

@@ -156,7 +156,6 @@ unuran_sources = [
 ]
 
 unuran_include_dirs = [
-  '../../_lib/src',  # for messagestream.h
   '../../_lib/unuran/unuran/src',
   '../../_lib/unuran/unuran/src/distr',
   '../../_lib/unuran/unuran/src/distributions',
@@ -228,7 +227,7 @@ py3.extension_module('unuran_wrapper',
   ],
   c_args: [unuran_defines, cython_c_args],
   include_directories: [unuran_include_dirs],
-  dependencies: np_dep,
+  dependencies: [np_dep, ccallback_dep],
   link_args: version_link_args,
   install: true,
   subdir: 'scipy/stats/_unuran'