8000 gh-126024: fix UBSan failure in `unicodeobject.c:find_first_nonascii` by picnixz · Pull Request #127566 · python/cpython · GitHub
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gh-126024: fix UBSan failure in unicodeobject.c:find_first_nonascii #127566

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Merged
merged 5 commits into from
Dec 6, 2024
Merged

gh-126024: fix UBSan failure in unicodeobject.c:find_first_nonascii #127566

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947fcfa
fix UBSan failure in `unicodeobject.c`
picnixz Dec 3, 2024
8d8fe33
fix compilation?
picnixz Dec 3, 2024
a807b63
simplify if-guards
picnixz Dec 3, 2024
c6af019
use memcpy() instead of `no_sanitize` features
picnixz Dec 5, 2024
5b957a8
Use `memcpy` on non-x86/amd64 little-endian platforms.
picnixz Dec 5, 2024
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22 changes: 18 additions & 4 deletions Objects/unicodeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5018,7 +5018,8 @@ ctz(size_t v)
#define HAVE_CTZ 0
#endif

#if HAVE_CTZ && PY_LITTLE_ENDIAN
#if PY_LITTLE_ENDIAN
# if HAVE_CTZ
// 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)
Expand Down Expand Up @@ -5064,7 +5065,21 @@ load_unaligned(const unsigned char *p, size_t size)
}
return u.s;
}
#endif
# endif
# if defined(_M_AMD64) || defined(_M_IX86) || defined(__x86_64__) || defined(__i386__)
// x86 and amd64 are little endian and can load unaligned memory.
# if defined(__clang__)
static inline size_t
__attribute__((no_sanitize("alignment")))
load_unaligned_x86_amd64(const unsigned char *p)
{
return *(const size_t *)p;
}
# else
# define load_unaligned_x86_amd64(p) *(const size_t *)p
# endif
# endif
#endif // PY_LITTLE_ENDIAN

/*
* Find the first non-ASCII character in a byte sequence.
Expand All @@ -5084,8 +5099,7 @@ find_first_nonascii(const unsigned char *start, const unsigned char *end)
#if PY_LITTLE_ENDIAN && HAVE_CTZ
if (p < p2) {
#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;
size_t u = load_unaligned_x86_amd64(p) & ASCII_CHAR_MASK;
#else
size_t u = load_unaligned(p, p2 - p) & ASCII_CHAR_MASK;
#endif
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