mirror of
https://github.com/python/cpython.git
synced 2025-10-30 21:21:22 +00:00
Give Python a debug-mode pymalloc, much as sketched on Python-Dev.
When WITH_PYMALLOC is defined, define PYMALLOC_DEBUG to enable the debug allocator. This can be done independent of build type (release or debug). A debug build automatically defines PYMALLOC_DEBUG when pymalloc is enabled. It's a detected error to define PYMALLOC_DEBUG when pymalloc isn't enabled. Two debugging entry points defined only under PYMALLOC_DEBUG: + _PyMalloc_DebugCheckAddress(const void *p) can be used (e.g., from gdb) to sanity-check a memory block obtained from pymalloc. It sprays info to stderr (see next) and dies via Py_FatalError if the block is detectably damaged. + _PyMalloc_DebugDumpAddress(const void *p) can be used to spray info about a debug memory block to stderr. A tiny start at implementing "API family" checks isn't good for anything yet. _PyMalloc_DebugRealloc() has been optimized to do little when the new size is <= old size. However, if the new size is larger, it really can't call the underlying realloc() routine without either violating its contract, or knowing something non-trivial about how the underlying realloc() works. A memcpy is always done in this case. This was a disaster for (and only) one of the std tests: test_bufio creates single text file lines up to a million characters long. On Windows, fileobject.c's get_line() uses the horridly funky getline_via_fgets(), which keeps growing and growing a string object hoping to find a newline. It grew the string object 1000 bytes each time, so for a million-character string it took approximately forever (I gave up after a few minutes). So, also: fileobject.c, getline_via_fgets(): When a single line is outrageously long, grow the string object at a mildly exponential rate, instead of just 1000 bytes at a time. That's enough so that a debug-build test_bufio finishes in about 5 seconds on my Win98SE box. I'm curious to try this on Win2K, because it has very different memory behavior than Win9X, and test_bufio always took a factor of 10 longer to complete on Win2K. It *could* be that the endless reallocs were simply killing it on Win2K even in the release build.
This commit is contained in:
Tim Peters
parent
91cc17d20e
commit
ddea208be9
4 changed files with 346 additions and 28 deletions
|
|
@ -61,6 +61,15 @@
|
|||
|
||||
#include "pyport.h"
|
||||
|
||||
/* Debug-mode build with pymalloc implies PYMALLOC_DEBUG.
|
||||
* PYMALLOC_DEBUG is in error if pymalloc is not in use.
|
||||
*/
|
||||
#if defined(Py_DEBUG) && defined(WITH_PYMALLOC) && !defined(PYMALLOC_DEBUG)
|
||||
#define PYMALLOC_DEBUG
|
||||
#endif
|
||||
#if defined(PYMALLOC_DEBUG) && !defined(WITH_PYMALLOC)
|
||||
#error "PYMALLOC_DEBUG requires WITH_PYMALLOC"
|
||||
#endif
|
||||
#include "pymem.h"
|
||||
|
||||
#include "object.h"
|
||||
|
|
|
|||
|
|
@ -95,14 +95,28 @@ extern DL_IMPORT(void) PyMem_Free(void *);
|
|||
DL_IMPORT(void *) _PyMalloc_Malloc(size_t nbytes);
|
||||
DL_IMPORT(void *) _PyMalloc_Realloc(void *p, size_t nbytes);
|
||||
DL_IMPORT(void) _PyMalloc_Free(void *p);
|
||||
|
||||
#ifdef PYMALLOC_DEBUG
|
||||
DL_IMPORT(void *) _PyMalloc_DebugMalloc(size_t nbytes, int family);
|
||||
DL_IMPORT(void *) _PyMalloc_DebugRealloc(void *p, size_t nbytes, int family);
|
||||
DL_IMPORT(void) _PyMalloc_DebugFree(void *p, int family);
|
||||
DL_IMPORT(void) _PyMalloc_DebugDumpAddress(const void *p);
|
||||
DL_IMPORT(void) _PyMalloc_DebugCheckAddress(const void *p);
|
||||
#define _PyMalloc_MALLOC(N) _PyMalloc_DebugMalloc(N, 0)
|
||||
#define _PyMalloc_REALLOC(P, N) _PyMalloc_DebugRealloc(P, N, 0)
|
||||
#define _PyMalloc_FREE(P) _PyMalloc_DebugFree(P, 0)
|
||||
|
||||
#else /* WITH_PYMALLOC && ! PYMALLOC_DEBUG */
|
||||
#define _PyMalloc_MALLOC _PyMalloc_Malloc
|
||||
#define _PyMalloc_REALLOC _PyMalloc_Realloc
|
||||
#define _PyMalloc_FREE _PyMalloc_Free
|
||||
#else
|
||||
#endif
|
||||
|
||||
#else /* ! WITH_PYMALLOC */
|
||||
#define _PyMalloc_MALLOC PyMem_MALLOC
|
||||
#define _PyMalloc_REALLOC PyMem_REALLOC
|
||||
#define _PyMalloc_FREE PyMem_FREE
|
||||
#endif
|
||||
#endif /* WITH_PYMALLOC */
|
||||
|
||||
|
||||
#ifdef __cplusplus
|
||||
|
|
|
|||
|
|
@ -772,13 +772,9 @@ getline_via_fgets(FILE *fp)
|
|||
* cautions about boosting that. 300 was chosen because the worst real-life
|
||||
* text-crunching job reported on Python-Dev was a mail-log crawler where over
|
||||
* half the lines were 254 chars.
|
||||
* INCBUFSIZE is the amount by which we grow the buffer, if MAXBUFSIZE isn't
|
||||
* enough. It doesn't much matter what this is set to: we only get here for
|
||||
* absurdly long lines anyway.
|
||||
*/
|
||||
#define INITBUFSIZE 100
|
||||
#define MAXBUFSIZE 300
|
||||
#define INCBUFSIZE 1000
|
||||
char* p; /* temp */
|
||||
char buf[MAXBUFSIZE];
|
||||
PyObject* v; /* the string object result */
|
||||
|
|
@ -786,6 +782,7 @@ getline_via_fgets(FILE *fp)
|
|||
char* pvend; /* address one beyond last free slot */
|
||||
size_t nfree; /* # of free buffer slots; pvend-pvfree */
|
||||
size_t total_v_size; /* total # of slots in buffer */
|
||||
size_t increment; /* amount to increment the buffer */
|
||||
|
||||
/* Optimize for normal case: avoid _PyString_Resize if at all
|
||||
* possible via first reading into stack buffer "buf".
|
||||
|
|
@ -853,7 +850,7 @@ getline_via_fgets(FILE *fp)
|
|||
/* The stack buffer isn't big enough; malloc a string object and read
|
||||
* into its buffer.
|
||||
*/
|
||||
total_v_size = MAXBUFSIZE + INCBUFSIZE;
|
||||
total_v_size = MAXBUFSIZE << 1;
|
||||
v = PyString_FromStringAndSize((char*)NULL, (int)total_v_size);
|
||||
if (v == NULL)
|
||||
return v;
|
||||
|
|
@ -897,7 +894,8 @@ getline_via_fgets(FILE *fp)
|
|||
}
|
||||
/* expand buffer and try again */
|
||||
assert(*(pvend-1) == '\0');
|
||||
total_v_size += INCBUFSIZE;
|
||||
increment = total_v_size >> 2; /* mild exponential growth */
|
||||
total_v_size += increment;
|
||||
if (total_v_size > INT_MAX) {
|
||||
PyErr_SetString(PyExc_OverflowError,
|
||||
"line is longer than a Python string can hold");
|
||||
|
|
@ -907,14 +905,13 @@ getline_via_fgets(FILE *fp)
|
|||
if (_PyString_Resize(&v, (int)total_v_size) < 0)
|
||||
return NULL;
|
||||
/* overwrite the trailing null byte */
|
||||
pvfree = BUF(v) + (total_v_size - INCBUFSIZE - 1);
|
||||
pvfree = BUF(v) + (total_v_size - increment - 1);
|
||||
}
|
||||
if (BUF(v) + total_v_size != p)
|
||||
_PyString_Resize(&v, p - BUF(v));
|
||||
return v;
|
||||
#undef INITBUFSIZE
|
||||
#undef MAXBUFSIZE
|
||||
#undef INCBUFSIZE
|
||||
}
|
||||
#endif /* ifdef USE_FGETS_IN_GETLINE */
|
||||
|
||||
|
|
|
|||
|
|
@ -623,24 +623,10 @@ _PyMalloc_Realloc(void *p, size_t nbytes)
|
|||
return (void *)bp;
|
||||
}
|
||||
|
||||
/* calloc */
|
||||
|
||||
/* -- unused --
|
||||
void *
|
||||
_PyMalloc_Calloc(size_t nbel, size_t elsz)
|
||||
{
|
||||
void *p;
|
||||
size_t nbytes;
|
||||
|
||||
nbytes = nbel * elsz;
|
||||
p = _PyMalloc_Malloc(nbytes);
|
||||
if (p != NULL)
|
||||
memset(p, 0, nbytes);
|
||||
return p;
|
||||
}
|
||||
*/
|
||||
|
||||
#else /* ! WITH_PYMALLOC */
|
||||
|
||||
/*==========================================================================*/
|
||||
/* pymalloc not enabled: Redirect the entry points to the PyMem family. */
|
||||
void *
|
||||
_PyMalloc_Malloc(size_t n)
|
||||
{
|
||||
|
|
@ -686,3 +672,315 @@ _PyMalloc_Del(PyObject *op)
|
|||
{
|
||||
_PyMalloc_FREE(op);
|
||||
}
|
||||
|
||||
#ifdef PYMALLOC_DEBUG
|
||||
/*==========================================================================*/
|
||||
/* A x-platform debugging allocator. */
|
||||
|
||||
#define PYMALLOC_CLEANBYTE 0xCB /* uninitialized memory */
|
||||
#define PYMALLOC_DEADBYTE 0xDB /* free()ed memory */
|
||||
#define PYMALLOC_FORBIDDENBYTE 0xFB /* unusable memory */
|
||||
|
||||
static ulong serialno = 0; /* incremented on each debug {m,re}alloc */
|
||||
|
||||
/* Read 4 bytes at p as a big-endian ulong. */
|
||||
static ulong
|
||||
read4(const void *p)
|
||||
{
|
||||
const unsigned char *q = (unsigned char *)p;
|
||||
return ((ulong)q[0] << 24) |
|
||||
((ulong)q[1] << 16) |
|
||||
((ulong)q[2] << 8) |
|
||||
(ulong)q[3];
|
||||
}
|
||||
|
||||
/* Write the 4 least-significant bytes of n as a big-endian unsigned int,
|
||||
MSB at address p, LSB at p+3. */
|
||||
static void
|
||||
write4(void *p, ulong n)
|
||||
{
|
||||
unsigned char *q = (unsigned char *)p;
|
||||
q[0] = (unsigned char)((n >> 24) & 0xff);
|
||||
q[1] = (unsigned char)((n >> 16) & 0xff);
|
||||
q[2] = (unsigned char)((n >> 8) & 0xff);
|
||||
q[3] = (unsigned char)( n & 0xff);
|
||||
}
|
||||
|
||||
static void
|
||||
check_family(const void *p, int family)
|
||||
{
|
||||
const uchar *q = (const uchar *)p;
|
||||
int original_family;
|
||||
char buf[200];
|
||||
|
||||
assert(p != NULL);
|
||||
original_family = (int)*(q-4);
|
||||
if (family != original_family) {
|
||||
/* XXX better msg */
|
||||
PyOS_snprintf(buf, sizeof(buf),
|
||||
"free or realloc from family #%d called, "
|
||||
"but block was allocated by family #%d",
|
||||
family, original_family);
|
||||
_PyMalloc_DebugDumpAddress(p);
|
||||
Py_FatalError(buf);
|
||||
}
|
||||
}
|
||||
|
||||
/* The debug malloc asks for 16 extra bytes and fills them with useful stuff,
|
||||
here calling the underlying malloc's result p:
|
||||
|
||||
p[0:4]
|
||||
Number of bytes originally asked for. 4-byte unsigned integer,
|
||||
big-endian (easier to read in a memory dump).
|
||||
p[4]
|
||||
The API "family" this malloc call belongs to. XXX todo XXX
|
||||
p[5:8]
|
||||
Copies of PYMALLOC_FORBIDDENBYTE. Used to catch under- writes
|
||||
and reads.
|
||||
p[8:8+n]
|
||||
The requested memory, filled with copies of PYMALLOC_CLEANBYTE.
|
||||
Used to catch reference to uninitialized memory.
|
||||
&p[8] is returned. Note that this is 8-byte aligned if PyMalloc
|
||||
handled the request itself.
|
||||
p[8+n:8+n+4]
|
||||
Copies of PYMALLOC_FORBIDDENBYTE. Used to catch over- writes
|
||||
and reads.
|
||||
p[8+n+4:8+n+8]
|
||||
A serial number, incremented by 1 on each call to _PyMalloc_DebugMalloc
|
||||
and _PyMalloc_DebugRealloc.
|
||||
4-byte unsigned integer, big-endian.
|
||||
If "bad memory" is detected later, the serial number gives an
|
||||
excellent way to set a breakpoint on the next run, to capture the
|
||||
instant at which this block was passed out.
|
||||
*/
|
||||
|
||||
void *
|
||||
_PyMalloc_DebugMalloc(size_t nbytes, int family)
|
||||
{
|
||||
uchar *p; /* base address of malloc'ed block */
|
||||
uchar *q; /* p + 8 + nbytes + */
|
||||
size_t total; /* nbytes + 16 */
|
||||
|
||||
assert(family == 0);
|
||||
|
||||
++serialno;
|
||||
total = nbytes + 16;
|
||||
if (total < nbytes || (total >> 31) > 1) {
|
||||
/* overflow, or we can't represent it in 4 bytes */
|
||||
/* Obscure: can't do (total >> 32) != 0 instead, because
|
||||
C doesn't define what happens for a right-shift of 32
|
||||
when size_t is a 32-bit type. At least C guarantees
|
||||
size_t is an unsigned type. */
|
||||
return NULL;
|
||||
}
|
||||
|
||||
p = _PyMalloc_Malloc(total); /* XXX derive from family */
|
||||
if (p == NULL)
|
||||
return NULL;
|
||||
|
||||
write4(p, nbytes);
|
||||
p[4] = (uchar)family;
|
||||
p[5] = p[6] = p[7] = PYMALLOC_FORBIDDENBYTE;
|
||||
|
||||
if (nbytes > 0)
|
||||
memset(p+8, PYMALLOC_CLEANBYTE, nbytes);
|
||||
|
||||
q = p + 8 + nbytes;
|
||||
q[0] = q[1] = q[2] = q[3] = PYMALLOC_FORBIDDENBYTE;
|
||||
write4(q+4, serialno);
|
||||
|
||||
return p+8;
|
||||
}
|
||||
|
||||
/* The debug free first uses the address to find the number of bytes
|
||||
originally asked for, then checks the 8 bytes on each end for
|
||||
sanity (in particular, that the PYMALLOC_FORBIDDENBYTEs are still
|
||||
intact).
|
||||
Then fills the original bytes with PYMALLOC_DEADBYTE.
|
||||
Then calls the underlying free.
|
||||
*/
|
||||
void
|
||||
_PyMalloc_DebugFree(void *p, int family)
|
||||
{
|
||||
uchar *q = (uchar*)p;
|
||||
size_t nbytes;
|
||||
|
||||
assert(family == 0);
|
||||
|
||||
if (p == NULL)
|
||||
return;
|
||||
check_family(p, family);
|
||||
_PyMalloc_DebugCheckAddress(p);
|
||||
nbytes = read4(q-8);
|
||||
if (nbytes > 0)
|
||||
memset(q, PYMALLOC_DEADBYTE, nbytes);
|
||||
_PyMalloc_Free(q-8); /* XXX derive from family */
|
||||
}
|
||||
|
||||
void *
|
||||
_PyMalloc_DebugRealloc(void *p, size_t nbytes, int family)
|
||||
{
|
||||
uchar *q = (uchar *)p;
|
||||
size_t original_nbytes;
|
||||
uchar *fresh; /* new memory block, if needed */
|
||||
|
||||
assert(family == 0);
|
||||
|
||||
if (p == NULL)
|
||||
return _PyMalloc_DebugMalloc(nbytes, family);
|
||||
|
||||
check_family(p, family);
|
||||
_PyMalloc_DebugCheckAddress(p);
|
||||
|
||||
original_nbytes = read4(q-8);
|
||||
if (nbytes == original_nbytes) {
|
||||
/* note that this case is likely to be common due to the
|
||||
way Python appends to lists */
|
||||
++serialno;
|
||||
write4(q + nbytes + 4, serialno);
|
||||
return p;
|
||||
}
|
||||
|
||||
if (nbytes < original_nbytes) {
|
||||
/* shrinking -- leave the guts alone, except to
|
||||
fill the excess with DEADBYTE */
|
||||
const size_t excess = original_nbytes - nbytes;
|
||||
++serialno;
|
||||
write4(q-8, nbytes);
|
||||
/* kill the excess bytes plus the trailing 8 pad bytes */
|
||||
memset(q + nbytes, PYMALLOC_DEADBYTE, excess + 8);
|
||||
q += nbytes;
|
||||
q[0] = q[1] = q[2] = q[3] = PYMALLOC_FORBIDDENBYTE;
|
||||
write4(q+4, serialno);
|
||||
return p;
|
||||
}
|
||||
|
||||
/* More memory is needed: get it, copy over the first original_nbytes
|
||||
of the original data, and free the original memory. */
|
||||
fresh = (uchar *)_PyMalloc_DebugMalloc(nbytes, family);
|
||||
if (fresh != NULL && original_nbytes > 0)
|
||||
memcpy(fresh, p, original_nbytes);
|
||||
_PyMalloc_DebugFree(p, family);
|
||||
return fresh;
|
||||
}
|
||||
|
||||
void
|
||||
_PyMalloc_DebugCheckAddress(const void *p)
|
||||
{
|
||||
const uchar *q = (const uchar *)p;
|
||||
char *msg = NULL;
|
||||
|
||||
if (p == NULL)
|
||||
msg = "didn't expect a NULL pointer";
|
||||
|
||||
else if (*(q-3) != PYMALLOC_FORBIDDENBYTE ||
|
||||
*(q-2) != PYMALLOC_FORBIDDENBYTE ||
|
||||
*(q-1) != PYMALLOC_FORBIDDENBYTE)
|
||||
msg = "bad leading pad byte";
|
||||
|
||||
else {
|
||||
const ulong nbytes = read4(q-8);
|
||||
const uchar *tail = q + nbytes;
|
||||
int i;
|
||||
for (i = 0; i < 4; ++i) {
|
||||
if (tail[i] != PYMALLOC_FORBIDDENBYTE) {
|
||||
msg = "bad trailing pad byte";
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
if (msg != NULL) {
|
||||
_PyMalloc_DebugDumpAddress(p);
|
||||
Py_FatalError(msg);
|
||||
}
|
||||
}
|
||||
|
||||
void
|
||||
_PyMalloc_DebugDumpAddress(const void *p)
|
||||
{
|
||||
const uchar *q = (const uchar *)p;
|
||||
const uchar *tail;
|
||||
ulong nbytes, serial;
|
||||
|
||||
fprintf(stderr, "Debug memory block at address p=%p:\n", p);
|
||||
if (p == NULL)
|
||||
return;
|
||||
|
||||
nbytes = read4(q-8);
|
||||
fprintf(stderr, " %lu bytes originally allocated\n", nbytes);
|
||||
fprintf(stderr, " from API family #%d\n", *(q-4));
|
||||
|
||||
/* In case this is nuts, check the pad bytes before trying to read up
|
||||
the serial number (the address deref could blow up). */
|
||||
|
||||
fprintf(stderr, " the 3 pad bytes at p-3 are ");
|
||||
if (*(q-3) == PYMALLOC_FORBIDDENBYTE &&
|
||||
*(q-2) == PYMALLOC_FORBIDDENBYTE &&
|
||||
*(q-1) == PYMALLOC_FORBIDDENBYTE) {
|
||||
fprintf(stderr, "PYMALLOC_FORBIDDENBYTE, as expected\n");
|
||||
}
|
||||
else {
|
||||
int i;
|
||||
fprintf(stderr, "not all PYMALLOC_FORBIDDENBYTE (0x%02x):\n",
|
||||
PYMALLOC_FORBIDDENBYTE);
|
||||
for (i = 3; i >= 1; --i) {
|
||||
const uchar byte = *(q-i);
|
||||
fprintf(stderr, " at p-%d: 0x%02x", i, byte);
|
||||
if (byte != PYMALLOC_FORBIDDENBYTE)
|
||||
fputs(" *** OUCH", stderr);
|
||||
fputc('\n', stderr);
|
||||
}
|
||||
}
|
||||
|
||||
tail = q + nbytes;
|
||||
fprintf(stderr, " the 4 pad bytes at tail=%p are ", tail);
|
||||
if (tail[0] == PYMALLOC_FORBIDDENBYTE &&
|
||||
tail[1] == PYMALLOC_FORBIDDENBYTE &&
|
||||
tail[2] == PYMALLOC_FORBIDDENBYTE &&
|
||||
tail[3] == PYMALLOC_FORBIDDENBYTE) {
|
||||
fprintf(stderr, "PYMALLOC_FORBIDDENBYTE, as expected\n");
|
||||
}
|
||||
else {
|
||||
int i;
|
||||
fprintf(stderr, "not all PYMALLOC_FORBIDDENBYTE (0x%02x):\n",
|
||||
PYMALLOC_FORBIDDENBYTE);
|
||||
for (i = 0; i < 4; ++i) {
|
||||
const uchar byte = tail[i];
|
||||
fprintf(stderr, " at tail+%d: 0x%02x",
|
||||
i, byte);
|
||||
if (byte != PYMALLOC_FORBIDDENBYTE)
|
||||
fputs(" *** OUCH", stderr);
|
||||
fputc('\n', stderr);
|
||||
}
|
||||
}
|
||||
|
||||
serial = read4(tail+4);
|
||||
fprintf(stderr, " the block was made by call #%lu to "
|
||||
"debug malloc/realloc\n", serial);
|
||||
|
||||
if (nbytes > 0) {
|
||||
int i = 0;
|
||||
fprintf(stderr, " data at p:");
|
||||
/* print up to 8 bytes at the start */
|
||||
while (q < tail && i < 8) {
|
||||
fprintf(stderr, " %02x", *q);
|
||||
++i;
|
||||
++q;
|
||||
}
|
||||
/* and up to 8 at the end */
|
||||
if (q < tail) {
|
||||
if (tail - q > 8) {
|
||||
fprintf(stderr, " ...");
|
||||
q = tail - 8;
|
||||
}
|
||||
while (q < tail) {
|
||||
fprintf(stderr, " %02x", *q);
|
||||
++q;
|
||||
}
|
||||
}
|
||||
fprintf(stderr, "\n");
|
||||
}
|
||||
}
|
||||
|
||||
#endif /* PYMALLOC_DEBUG */
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue