pythongh-101408: use _PyType_PreHeaderSize in more places

faster-cpython · Feb 19, 2023 · 0ef500e · 0ef500e
1 parent fdc1aa9
commit 0ef500e
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Showing 3 changed files with 14 additions and 24 deletions.
diff --git a/Modules/_tracemalloc.c b/Modules/_tracemalloc.c
@@ -2,6 +2,7 @@
 #include "pycore_fileutils.h"     // _Py_write_noraise()
 #include "pycore_gc.h"            // PyGC_Head
 #include "pycore_hashtable.h"     // _Py_hashtable_t
+#include "pycore_object.h"        // _PyType_PreHeaderSize
 #include "pycore_pymem.h"         // _Py_tracemalloc_config
 #include "pycore_runtime.h"       // _Py_ID()
 #include "pycore_traceback.h"
@@ -1399,19 +1400,13 @@ static PyObject *
 _tracemalloc__get_object_traceback(PyObject *module, PyObject *obj)
 /*[clinic end generated code: output=41ee0553a658b0aa input=29495f1b21c53212]*/
 {
-    PyTypeObject *type;
-    void *ptr;
+    uintptr_t ptr;
     traceback_t *traceback;
 
-    type = Py_TYPE(obj);
-    if (PyType_IS_GC(type)) {
-        ptr = (void *)((char *)obj - sizeof(PyGC_Head));
-    }
-    else {
-        ptr = (void *)obj;
-    }
+    ptr = (uintptr_t)obj;
+    ptr -= _PyType_PreHeaderSize(Py_TYPE(obj));
 
-    traceback = tracemalloc_get_traceback(DEFAULT_DOMAIN, (uintptr_t)ptr);
+    traceback = tracemalloc_get_traceback(DEFAULT_DOMAIN, ptr);
     if (traceback == NULL)
         Py_RETURN_NONE;
 

diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
@@ -2348,17 +2348,18 @@ _PyObject_GC_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
 PyVarObject *
 _PyObject_GC_Resize(PyVarObject *op, Py_ssize_t nitems)
 {
+    size_t presize = _PyType_PreHeaderSize(Py_TYPE(op));
     const size_t basicsize = _PyObject_VAR_SIZE(Py_TYPE(op), nitems);
     _PyObject_ASSERT((PyObject *)op, !_PyObject_GC_IS_TRACKED(op));
-    if (basicsize > (size_t)PY_SSIZE_T_MAX - sizeof(PyGC_Head)) {
+    if (basicsize > (size_t)PY_SSIZE_T_MAX - presize) {
         return (PyVarObject *)PyErr_NoMemory();
     }
 
-    PyGC_Head *g = AS_GC(op);
-    g = (PyGC_Head *)PyObject_Realloc(g,  sizeof(PyGC_Head) + basicsize);
-    if (g == NULL)
+    char *mem = (char *)op - presize;
+    mem = PyObject_Realloc(mem,  presize + basicsize);
+    if (mem == NULL)
         return (PyVarObject *)PyErr_NoMemory();
-    op = (PyVarObject *) FROM_GC(g);
+    op = (PyVarObject *) (mem + presize);
     Py_SET_SIZE(op, nitems);
     return op;
 }

diff --git a/Objects/object.c b/Objects/object.c
@@ -2342,15 +2342,9 @@ _PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
         /* Display the traceback where the object has been allocated.
            Do it before dumping repr(obj), since repr() is more likely
            to crash than dumping the traceback. */
-        void *ptr;
-        PyTypeObject *type = Py_TYPE(obj);
-        if (_PyType_IS_GC(type)) {
-            ptr = (void *)((char *)obj - sizeof(PyGC_Head));
-        }
-        else {
-            ptr = (void *)obj;
-        }
-        _PyMem_DumpTraceback(fileno(stderr), ptr);
+        char *mem = (char *)obj;
+        mem -= _PyType_PreHeaderSize(Py_TYPE(obj));
+        _PyMem_DumpTraceback(fileno(stderr), mem);
 
         /* This might succeed or fail, but we're about to abort, so at least
            try to provide any extra info we can: */