diff options
Diffstat (limited to 'Misc/SpecialBuilds.txt')
| -rw-r--r-- | Misc/SpecialBuilds.txt | 32 |
1 files changed, 18 insertions, 14 deletions
diff --git a/Misc/SpecialBuilds.txt b/Misc/SpecialBuilds.txt index e0b3315..952ca42 100644 --- a/Misc/SpecialBuilds.txt +++ b/Misc/SpecialBuilds.txt @@ -96,16 +96,16 @@ dynamically allocated memory blocks. The special bit patterns are: Strings of these bytes are unlikely to be valid addresses, floats, or 7-bit ASCII strings. -8 bytes are added at each end of each block of N bytes requested. The -memory layout is like so, where p represents the address returned by a -malloc-like or realloc-like function (p[i:j] means the slice of bytes -from *(p+i) inclusive up to *(p+j) exclusive; note that the treatment -of negative indices differs from a Python slice): - -p[-8:-4] - Number of bytes originally asked for. 4-byte unsigned integer, - big-endian (easier to read in a memory dump). -p[-4:0] +Let S = sizeof(size_t). 2*S bytes are added at each end of each block of N +bytes requested. The memory layout is like so, where p represents the +address returned by a malloc-like or realloc-like function (p[i:j] means +the slice of bytes from *(p+i) inclusive up to *(p+j) exclusive; note that +the treatment of negative indices differs from a Python slice): + +p[-2*S:-S] + Number of bytes originally asked for. This is a size_t, big-endian + (easier to read in a memory dump). +p[-S:0] Copies of FORBIDDENBYTE. Used to catch under- writes and reads. p[0:N] The requested memory, filled with copies of CLEANBYTE, used to catch @@ -116,12 +116,12 @@ p[0:N] DEADBYTE, to catch reference to freed memory. When a realloc- like function is called requesting a smaller memory block, the excess old bytes are also filled with DEADBYTE. -p[N:N+4] +p[N:N+S] Copies of FORBIDDENBYTE. Used to catch over- writes and reads. -p[N+4:N+8] +p[N+S:N+2*S] A serial number, incremented by 1 on each call to a malloc-like or realloc-like function. - 4-byte unsigned integer, big-endian. + Big-endian size_t. 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. The static function @@ -145,6 +145,10 @@ envar PYTHONMALLOCSTATS If this envar exists, a report of pymalloc summary statistics is printed to stderr whenever a new arena is allocated, and also by Py_Finalize(). + +Changed in 2.5: The number of extra bytes allocated is 4*sizeof(size_t). +Before it was 16 on all boxes, reflecting that Python couldn't make use of +allocations >= 2**32 bytes even on 64-bit boxes before 2.5. --------------------------------------------------------------------------- Py_DEBUG introduced in 1.5 named DEBUG before 1.5 @@ -251,7 +255,7 @@ is not defined by the architecture specification, so you'll need to find the manual for your specific processor. For the 750CX, 750CXe and 750FX (all sold as the G3) we find: - The time base counter is clocked at a frequency that is + The time base counter is clocked at a frequency that is one-fourth that of the bus clock. This build is enabled by the --with-tsc flag to configure. |