https://github.com/python/cpython/commit/83d8134c5b13a1c2f26176a60d5b1e3478fe92bd
commit: 83d8134c5b13a1c2f26176a60d5b1e3478fe92bd
branch: main
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2025-11-27T12:32:31+01:00
summary:
gh-127635: Use flexible array in tracemalloc (#141991)
Replace frames[1] with frames[] in tracemalloc_traceback structure.
files:
M Include/internal/pycore_tracemalloc.h
M Python/tracemalloc.c
diff --git a/Include/internal/pycore_tracemalloc.h
b/Include/internal/pycore_tracemalloc.h
index 572e8025876319..693385f9a46d12 100644
--- a/Include/internal/pycore_tracemalloc.h
+++ b/Include/internal/pycore_tracemalloc.h
@@ -30,8 +30,8 @@ struct _PyTraceMalloc_Config {
};
-/* Pack the frame_t structure to reduce the memory footprint on 64-bit
- architectures: 12 bytes instead of 16. */
+/* Pack the tracemalloc_frame and tracemalloc_traceback structures to reduce
+ the memory footprint on 64-bit architectures: 12 bytes instead of 16. */
#if defined(_MSC_VER)
#pragma pack(push, 4)
#endif
@@ -46,18 +46,22 @@ tracemalloc_frame {
PyObject *filename;
unsigned int lineno;
};
-#ifdef _MSC_VER
-#pragma pack(pop)
-#endif
-struct tracemalloc_traceback {
+struct
+#ifdef __GNUC__
+__attribute__((packed))
+#endif
+tracemalloc_traceback {
Py_uhash_t hash;
/* Number of frames stored */
uint16_t nframe;
/* Total number of frames the traceback had */
uint16_t total_nframe;
- struct tracemalloc_frame frames[1];
+ struct tracemalloc_frame frames[];
};
+#ifdef _MSC_VER
+#pragma pack(pop)
+#endif
struct _tracemalloc_runtime_state {
@@ -95,7 +99,7 @@ struct _tracemalloc_runtime_state {
Protected by TABLES_LOCK(). */
_Py_hashtable_t *domains;
- struct tracemalloc_traceback empty_traceback;
+ struct tracemalloc_traceback *empty_traceback;
Py_tss_t reentrant_key;
};
diff --git a/Python/tracemalloc.c b/Python/tracemalloc.c
index 005bdd378289e7..20351618721c3b 100644
--- a/Python/tracemalloc.c
+++ b/Python/tracemalloc.c
@@ -46,7 +46,7 @@ typedef struct tracemalloc_frame frame_t;
typedef struct tracemalloc_traceback traceback_t;
#define TRACEBACK_SIZE(NFRAME) \
- (sizeof(traceback_t) + sizeof(frame_t) * (NFRAME - 1))
+ (sizeof(traceback_t) + sizeof(frame_t) * (NFRAME))
static const int MAX_NFRAME = UINT16_MAX;
@@ -329,8 +329,9 @@ traceback_new(void)
traceback->nframe = 0;
traceback->total_nframe = 0;
traceback_get_frames(traceback);
- if (traceback->nframe == 0)
- return &tracemalloc_empty_traceback;
+ if (traceback->nframe == 0) {
+ return tracemalloc_empty_traceback;
+ }
traceback->hash = traceback_hash(traceback);
/* intern the traceback */
@@ -754,12 +755,18 @@ _PyTraceMalloc_Init(void)
return _PyStatus_NO_MEMORY();
}
- tracemalloc_empty_traceback.nframe = 1;
- tracemalloc_empty_traceback.total_nframe = 1;
+ assert(tracemalloc_empty_traceback == NULL);
+ tracemalloc_empty_traceback = raw_malloc(TRACEBACK_SIZE(1));
+ if (tracemalloc_empty_traceback == NULL) {
+ return _PyStatus_NO_MEMORY();
+ }
+
+ tracemalloc_empty_traceback->nframe = 1;
+ tracemalloc_empty_traceback->total_nframe = 1;
/* borrowed reference */
- tracemalloc_empty_traceback.frames[0].filename = &_Py_STR(anon_unknown);
- tracemalloc_empty_traceback.frames[0].lineno = 0;
- tracemalloc_empty_traceback.hash =
traceback_hash(&tracemalloc_empty_traceback);
+ tracemalloc_empty_traceback->frames[0].filename = &_Py_STR(anon_unknown);
+ tracemalloc_empty_traceback->frames[0].lineno = 0;
+ tracemalloc_empty_traceback->hash =
traceback_hash(tracemalloc_empty_traceback);
tracemalloc_config.initialized = TRACEMALLOC_INITIALIZED;
return _PyStatus_OK();
@@ -782,6 +789,9 @@ tracemalloc_deinit(void)
_Py_hashtable_destroy(tracemalloc_filenames);
PyThread_tss_delete(&tracemalloc_reentrant_key);
+
+ raw_free(tracemalloc_empty_traceback);
+ tracemalloc_empty_traceback = NULL;
}
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