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gh-127417: fix assertion error on AIX #127433

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Merged
merged 5 commits into from
Nov 30, 2024
Merged

gh-127417: fix assertion error on AIX #127433

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6dafd9a
fix assertion error on AIX
methane Nov 30, 2024
2faf883
fix 32bit build
methane Nov 30, 2024
ba3e008
fix for big endian
methane Nov 30, 2024
47e7bc5
Merge branch 'main' into fix-127417
methane Nov 30, 2024
aa4a839
fixup
methane Nov 30, 2024
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24 changes: 14 additions & 10 deletions Objects/unicodeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5014,21 +5014,26 @@ ctz(size_t v)
#endif /* SIZEOF_SIZE_T */
return pos;
}
#else
#define HAVE_CTZ 0
#endif

#if HAVE_CTZ
// load p[0]..p[size-1] as a little-endian size_t
// without unaligned access nor read ahead.
#if HAVE_CTZ && PY_LITTLE_ENDIAN
// load p[0]..p[size-1] as a size_t without unaligned access nor read ahead.
static size_t
load_unaligned(const unsigned char *p, size_t size)
{
assert(size <= SIZEOF_SIZE_T);
union {
size_t s;
unsigned char b[SIZEOF_SIZE_T];
} u;
u.s = 0;
// This switch statement assumes little endian because:
// * union is faster than bitwise or and shift.
// * big endian machine is rare and hard to maintain.
switch (size) {
default:
#if SIZEOF_SIZE_T == 8
case 8:
u.b[7] = p[7];
_Py_FALLTHROUGH;
Expand All @@ -5041,6 +5046,7 @@ load_unaligned(const unsigned char *p, size_t size)
case 5:
u.b[4] = p[4];
_Py_FALLTHROUGH;
#endif
case 4:
u.b[3] = p[3];
_Py_FALLTHROUGH;
Expand All @@ -5055,8 +5061,6 @@ load_unaligned(const unsigned char *p, size_t size)
break;
case 0:
break;
default:
Py_UNREACHABLE();
}
return u.s;
}
Expand All @@ -5077,20 +5081,20 @@ find_first_nonascii(const unsigned char *start, const unsigned char *end)

if (end - start >= SIZEOF_SIZE_T) {
const unsigned char *p2 = _Py_ALIGN_UP(p, SIZEOF_SIZE_T);
#if PY_LITTLE_ENDIAN && HAVE_CTZ
if (p < p2) {
#if HAVE_CTZ
#if defined(_M_AMD64) || defined(_M_IX86) || defined(__x86_64__) || defined(__i386__)
// x86 and amd64 are little endian and can load unaligned memory.
size_t u = *(const size_t*)p & ASCII_CHAR_MASK;
#else
size_t u = load_unaligned(p, p2 - p) & ASCII_CHAR_MASK;
#endif
if (u) {
return p - start + (ctz(u) - 7) / 8;
return (ctz(u) - 7) / 8;
}
p = p2;
}
#else
#else /* PY_LITTLE_ENDIAN && HAVE_CTZ */
while (p < p2) {
if (*p & 0x80) {
return p - start;
Expand All @@ -5113,7 +5117,7 @@ find_first_nonascii(const unsigned char *start, const unsigned char *end)
p += SIZEOF_SIZE_T;
}
}
#if HAVE_CTZ
#if PY_LITTLE_ENDIAN && HAVE_CTZ
// we can not use *(const size_t*)p to avoid buffer overrun.
size_t u = load_unaligned(p, end - p) & ASCII_CHAR_MASK;
if (u) {
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