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| author | Jessica Clarke <jrtc27@jrtc27.com> | 2021-03-31 10:12:39 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2021-03-31 10:12:39 (GMT) |
| commit | dec075754960dd85972ce5170df76e862f966132 (patch) | |
| tree | d03d976a2f077f0f07ebfd9ed35f2c91490de89d /PC | |
| parent | cfa176685a5e788bafc7749d7a93f43ea3e4de9f (diff) | |
| download | cpython-dec075754960dd85972ce5170df76e862f966132.zip cpython-dec075754960dd85972ce5170df76e862f966132.tar.gz cpython-dec075754960dd85972ce5170df76e862f966132.tar.bz2 | |
bpo-43179: Generalise alignment for optimised string routines (GH-24624)
* Remove m68k-specific hack from ascii_decode
On m68k, alignments of primitives is more relaxed, with 4-byte and
8-byte types only requiring 2-byte alignment, thus using sizeof(size_t)
does not work. Instead, use the portable alternative.
Note that this is a minimal fix that only relaxes the assertion and the
condition for when to use the optimised version remains overly strict.
Such issues will be fixed tree-wide in the next commit.
NB: In C11 we could use _Alignof(size_t) instead, but for compatibility
we use autoconf.
* Optimise string routines for architectures with non-natural alignment
C only requires that sizeof(x) is a multiple of alignof(x), not that the
two are equal. Thus anywhere where we optimise based on alignment we
should be using alignof(x) not sizeof(x).
This is more annoying than it would be in C11 where we could just use
_Alignof(x) (and alignof(x) in C++11), but since we still require only
C99 we must plumb the information all the way from autoconf through the
various typedefs and defines.
Diffstat (limited to 'PC')
| -rw-r--r-- | PC/pyconfig.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/PC/pyconfig.h b/PC/pyconfig.h index 00a65b2..103e647 100644 --- a/PC/pyconfig.h +++ b/PC/pyconfig.h @@ -289,6 +289,7 @@ Py_NO_ENABLE_SHARED to find out. Also support MS_NO_COREDLL for b/w compat */ # define SIZEOF_FPOS_T 8 # define SIZEOF_HKEY 8 # define SIZEOF_SIZE_T 8 +# define ALIGNOF_SIZE_T 8 /* configure.ac defines HAVE_LARGEFILE_SUPPORT iff sizeof(off_t) > sizeof(long), and sizeof(long long) >= sizeof(off_t). On Win64 the second condition is not true, but if fpos_t replaces off_t @@ -303,6 +304,7 @@ Py_NO_ENABLE_SHARED to find out. Also support MS_NO_COREDLL for b/w compat */ # define SIZEOF_FPOS_T 8 # define SIZEOF_HKEY 4 # define SIZEOF_SIZE_T 4 +# define ALIGNOF_SIZE_T 4 /* MS VS2005 changes time_t to a 64-bit type on all platforms */ # if defined(_MSC_VER) && _MSC_VER >= 1400 # define SIZEOF_TIME_T 8 @@ -321,6 +323,7 @@ Py_NO_ENABLE_SHARED to find out. Also support MS_NO_COREDLL for b/w compat */ #define SIZEOF_SHORT 2 #define SIZEOF_INT 4 #define SIZEOF_LONG 4 +#define ALIGNOF_LONG 4 #define SIZEOF_LONG_LONG 8 #define SIZEOF_DOUBLE 8 #define SIZEOF_FLOAT 4 |