bpo-36346: Make using the legacy Unicode C API optional (GH-21437)

Add compile time option USE_UNICODE_WCHAR_CACHE. Setting it to 0
makes the interpreter not using the wchar_t cache and the legacy Unicode C API.

1 files changed, 58 insertions, 23 deletions

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 648dd15ca09..2e1045ad3a7 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -3150,9 +3150,11 @@ unicode_get_widechar_size(PyObject *unicode)
     assert(unicode != NULL);
     assert(_PyUnicode_CHECK(unicode));
 
+#if USE_UNICODE_WCHAR_CACHE
     if (_PyUnicode_WSTR(unicode) != NULL) {
         return PyUnicode_WSTR_LENGTH(unicode);
     }
+#endif /* USE_UNICODE_WCHAR_CACHE */
     assert(PyUnicode_IS_READY(unicode));
 
     res = _PyUnicode_LENGTH(unicode);
@@ -3173,16 +3175,21 @@ unicode_get_widechar_size(PyObject *unicode)
 static void
 unicode_copy_as_widechar(PyObject *unicode, wchar_t *w, Py_ssize_t size)
 {
-    const wchar_t *wstr;
-
     assert(unicode != NULL);
     assert(_PyUnicode_CHECK(unicode));
 
-    wstr = _PyUnicode_WSTR(unicode);
+#if USE_UNICODE_WCHAR_CACHE
+    const wchar_t *wstr = _PyUnicode_WSTR(unicode);
     if (wstr != NULL) {
         memcpy(w, wstr, size * sizeof(wchar_t));
         return;
     }
+#else /* USE_UNICODE_WCHAR_CACHE */
+    if (PyUnicode_KIND(unicode) == sizeof(wchar_t)) {
+        memcpy(w, PyUnicode_DATA(unicode), size * sizeof(wchar_t));
+        return;
+    }
+#endif /* USE_UNICODE_WCHAR_CACHE */
     assert(PyUnicode_IS_READY(unicode));
 
     if (PyUnicode_KIND(unicode) == PyUnicode_1BYTE_KIND) {
@@ -4378,7 +4385,6 @@ unicode_decode_call_errorhandler_wchar(
     Py_ssize_t requiredsize;
     Py_ssize_t newpos;
     PyObject *inputobj = NULL;
-    wchar_t *repwstr;
     Py_ssize_t repwlen;
 
     if (*errorHandler == NULL) {
@@ -4424,9 +4430,19 @@ unicode_decode_call_errorhandler_wchar(
         goto onError;
     }
 
-    repwstr = PyUnicode_AsUnicodeAndSize(repunicode, &repwlen);
-    if (repwstr == NULL)
+#if USE_UNICODE_WCHAR_CACHE
+_Py_COMP_DIAG_PUSH
+_Py_COMP_DIAG_IGNORE_DEPR_DECLS
+    repwlen = PyUnicode_GetSize(repunicode);
+    if (repwlen < 0)
+        goto onError;
+_Py_COMP_DIAG_POP
+#else /* USE_UNICODE_WCHAR_CACHE */
+    repwlen = PyUnicode_AsWideChar(repunicode, NULL, 0);
+    if (repwlen < 0)
         goto onError;
+    repwlen--;
+#endif /* USE_UNICODE_WCHAR_CACHE */
     /* need more space? (at least enough for what we
        have+the replacement+the rest of the string (starting
        at the new input position), so we won't have to check space
@@ -4446,7 +4462,7 @@ unicode_decode_call_errorhandler_wchar(
             goto onError;
         }
     }
-    wcsncpy(*buf + *outpos, repwstr, repwlen);
+    PyUnicode_AsWideChar(repunicode, *buf + *outpos, repwlen);
     *outpos += repwlen;
     *endinpos = newpos;
     *inptr = *input + newpos;
@@ -7748,6 +7764,7 @@ encode_code_page_strict(UINT code_page, PyObject **outbytes,
     /* Create a substring so that we can get the UTF-16 representation
        of just the slice under consideration. */
     PyObject *substring;
+    int ret = -1;
 
     assert(len > 0);
 
@@ -7759,11 +7776,22 @@ encode_code_page_strict(UINT code_page, PyObject **outbytes,
     substring = PyUnicode_Substring(unicode, offset, offset+len);
     if (substring == NULL)
         return -1;
+#if USE_UNICODE_WCHAR_CACHE
+_Py_COMP_DIAG_PUSH
+_Py_COMP_DIAG_IGNORE_DEPR_DECLS
     p = PyUnicode_AsUnicodeAndSize(substring, &size);
     if (p == NULL) {
         Py_DECREF(substring);
         return -1;
     }
+_Py_COMP_DIAG_POP
+#else /* USE_UNICODE_WCHAR_CACHE */
+    p = PyUnicode_AsWideCharString(substring, &size);
+    Py_CLEAR(substring);
+    if (p == NULL) {
+        return -1;
+    }
+#endif /* USE_UNICODE_WCHAR_CACHE */
     assert(size <= INT_MAX);
 
     /* First get the size of the result */
@@ -7775,16 +7803,15 @@ encode_code_page_strict(UINT code_page, PyObject **outbytes,
         goto error;
     /* If we used a default char, then we failed! */
     if (pusedDefaultChar && *pusedDefaultChar) {
-        Py_DECREF(substring);
-        return -2;
+        ret = -2;
+        goto done;
     }
 
     if (*outbytes == NULL) {
         /* Create string object */
         *outbytes = PyBytes_FromStringAndSize(NULL, outsize);
         if (*outbytes == NULL) {
-            Py_DECREF(substring);
-            return -1;
+            goto done;
         }
         out = PyBytes_AS_STRING(*outbytes);
     }
@@ -7793,12 +7820,10 @@ encode_code_page_strict(UINT code_page, PyObject **outbytes,
         const Py_ssize_t n = PyBytes_Size(*outbytes);
         if (outsize > PY_SSIZE_T_MAX - n) {
             PyErr_NoMemory();
-            Py_DECREF(substring);
-            return -1;
+            goto done;
         }
         if (_PyBytes_Resize(outbytes, n + outsize) < 0) {
-            Py_DECREF(substring);
-            return -1;
+            goto done;
         }
         out = PyBytes_AS_STRING(*outbytes) + n;
     }
@@ -7808,19 +7833,29 @@ encode_code_page_strict(UINT code_page, PyObject **outbytes,
                                   p, (int)size,
                                   out, outsize,
                                   NULL, pusedDefaultChar);
-    Py_CLEAR(substring);
     if (outsize <= 0)
         goto error;
-    if (pusedDefaultChar && *pusedDefaultChar)
-        return -2;
-    return 0;
+    if (pusedDefaultChar && *pusedDefaultChar) {
+        ret = -2;
+        goto done;
+    }
+    ret = 0;
+
+done:
+#if USE_UNICODE_WCHAR_CACHE
+    Py_DECREF(substring);
+#else /* USE_UNICODE_WCHAR_CACHE */
+    PyMem_Free(p);
+#endif /* USE_UNICODE_WCHAR_CACHE */
+    return ret;
 
 error:
-    Py_XDECREF(substring);
-    if (GetLastError() == ERROR_NO_UNICODE_TRANSLATION)
-        return -2;
+    if (GetLastError() == ERROR_NO_UNICODE_TRANSLATION) {
+        ret = -2;
+        goto done;
+    }
     PyErr_SetFromWindowsErr(0);
-    return -1;
+    goto done;
 }
 
 /*