gh-123229: Fix valgrind warning by initializing the f-string buffers to 0 in the tokenizer (#123263)

Signed-off-by: Pablo Galindo <[email protected]>

Author: pablogsal

Misc/NEWS.d/next/Core and Builtins/2024-08-23-13-08-27.gh-issue-123229.aHm-dw.rst

@@ -0,0 +1,2 @@
+Fix valgrind warning by initializing the f-string buffers to 0 in the
+tokenizer. Patch by Pablo Galindo

Parser/lexer/state.c

@@ -12,7 +12,8 @@
 struct tok_state *
 _PyTokenizer_tok_new(void)
 {
-    struct tok_state *tok = (struct tok_state *)PyMem_Malloc(
+    struct tok_state *tok = (struct tok_state *)PyMem_Calloc(
+                                            1,
                                             sizeof(struct tok_state));
     if (tok == NULL)
         return NULL;