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gh-127635: Use flexible array in tracemalloc (#141991)

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Replace frames[1] with frames[] in tracemalloc_traceback structure.
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Victor Stinner 2025-11-27 12:32:31 +01:00 • committed by GitHub
parent 7fe1a18b77
commit 83d8134c5b
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2 changed files with 30 additions and 16 deletions
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20
Include/internal/pycore_tracemalloc.h
View file

@ -30,8 +30,8 @@ struct _PyTraceMalloc_Config {
}; };
/* Pack the frame_t structure to reduce the memory footprint on 64-bit /* Pack the tracemalloc_frame and tracemalloc_traceback structures to reduce
architectures: 12 bytes instead of 16. */ the memory footprint on 64-bit architectures: 12 bytes instead of 16. */
#if defined(_MSC_VER) #if defined(_MSC_VER)
#pragma pack(push, 4) #pragma pack(push, 4)
#endif #endif
@ -46,18 +46,22 @@ tracemalloc_frame {
PyObject *filename; PyObject *filename;
unsigned int lineno; 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; Py_uhash_t hash;
/* Number of frames stored */ /* Number of frames stored */
uint16_t nframe; uint16_t nframe;
/* Total number of frames the traceback had */ /* Total number of frames the traceback had */
uint16_t total_nframe; uint16_t total_nframe;
struct tracemalloc_frame frames[1]; struct tracemalloc_frame frames[];
}; };
#ifdef _MSC_VER
#pragma pack(pop)
#endif
struct _tracemalloc_runtime_state { struct _tracemalloc_runtime_state {
@ -95,7 +99,7 @@ struct _tracemalloc_runtime_state {
Protected by TABLES_LOCK(). */ Protected by TABLES_LOCK(). */
_Py_hashtable_t *domains; _Py_hashtable_t *domains;
struct tracemalloc_traceback empty_traceback; struct tracemalloc_traceback *empty_traceback;
Py_tss_t reentrant_key; Py_tss_t reentrant_key;
}; };

26
Python/tracemalloc.c
View file

@ -46,7 +46,7 @@ typedef struct tracemalloc_frame frame_t;
typedef struct tracemalloc_traceback traceback_t; typedef struct tracemalloc_traceback traceback_t;
#define TRACEBACK_SIZE(NFRAME) \ #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; static const int MAX_NFRAME = UINT16_MAX;
@ -329,8 +329,9 @@ traceback_new(void)
traceback->nframe = 0; traceback->nframe = 0;
traceback->total_nframe = 0; traceback->total_nframe = 0;
traceback_get_frames(traceback); traceback_get_frames(traceback);
if (traceback->nframe == 0) if (traceback->nframe == 0) {
return &tracemalloc_empty_traceback; return tracemalloc_empty_traceback;
}
traceback->hash = traceback_hash(traceback); traceback->hash = traceback_hash(traceback);
/* intern the traceback */ /* intern the traceback */
@ -754,12 +755,18 @@ _PyTraceMalloc_Init(void)
return _PyStatus_NO_MEMORY(); return _PyStatus_NO_MEMORY();
} }
tracemalloc_empty_traceback.nframe = 1; assert(tracemalloc_empty_traceback == NULL);
tracemalloc_empty_traceback.total_nframe = 1; 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 */ /* borrowed reference */
tracemalloc_empty_traceback.frames[0].filename = &_Py_STR(anon_unknown); tracemalloc_empty_traceback->frames[0].filename = &_Py_STR(anon_unknown);
tracemalloc_empty_traceback.frames[0].lineno = 0; tracemalloc_empty_traceback->frames[0].lineno = 0;
tracemalloc_empty_traceback.hash = traceback_hash(&tracemalloc_empty_traceback); tracemalloc_empty_traceback->hash = traceback_hash(tracemalloc_empty_traceback);
tracemalloc_config.initialized = TRACEMALLOC_INITIALIZED; tracemalloc_config.initialized = TRACEMALLOC_INITIALIZED;
return _PyStatus_OK(); return _PyStatus_OK();
@ -782,6 +789,9 @@ tracemalloc_deinit(void)
_Py_hashtable_destroy(tracemalloc_filenames); _Py_hashtable_destroy(tracemalloc_filenames);
PyThread_tss_delete(&tracemalloc_reentrant_key); PyThread_tss_delete(&tracemalloc_reentrant_key);
raw_free(tracemalloc_empty_traceback);
tracemalloc_empty_traceback = NULL;
} }