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Add casts to type conversion to fix long dbl bug (#3038)

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If a user buffer is misaligned in the type conversion code, memcpy
could fail if the call is SSE-optimized by the compiler. This change
adds uint8_t * casts so the compiler won't make optimistic assumptions
about buffer alignment.
This commit is contained in:
Dana Robinson 2023-06-03 07:23:35 -07:00 committed by GitHub
parent 81bc34ac4c
commit e3559c7b64
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 22 additions and 2 deletions
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24
src/H5Tconv.c
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@ -887,7 +887,17 @@ done:
/* Macro defining action on source data which needs to be aligned (before main action) */
#define H5T_CONV_LOOP_PRE_SALIGN(ST) \
{ \
H5MM_memcpy(&src_aligned, src, sizeof(ST)); \
/* The uint8_t * cast is required to avoid tripping over undefined behavior. \
* \
* The typed pointer arrives via a void pointer, which may have any alignment. \
* We then cast it to a pointer to a type that is assumed to be aligned, which \
* is undefined behavior (section 6.3.2.3 paragraph 7 of the C99 standard). \
* In the past this hasn't caused many problems, but in some cases (e.g. \
* converting long doubles on macOS), an optimizing compiler might do the \
* wrong thing (in the macOS case, the conversion uses SSE, which has stricter \
* requirements about alignment). \
*/ \
H5MM_memcpy(&src_aligned, (const uint8_t *)src, sizeof(ST)); \
}
/* Macro defining action on source data which doesn't need to be aligned (before main action) */
@ -919,7 +929,17 @@ done:
/* Macro defining action on destination data which needs to be aligned (after main action) */
#define H5T_CONV_LOOP_POST_DALIGN(DT) \
{ \
H5MM_memcpy(dst, &dst_aligned, sizeof(DT)); \
/* The uint8_t * cast is required to avoid tripping over undefined behavior. \
* \
* The typed pointer arrives via a void pointer, which may have any alignment. \
* We then cast it to a pointer to a type that is assumed to be aligned, which \
* is undefined behavior (section 6.3.2.3 paragraph 7 of the C99 standard). \
* In the past this hasn't caused many problems, but in some cases (e.g. \
* converting long doubles on macOS), an optimizing compiler might do the \
* wrong thing (in the macOS case, the conversion uses SSE, which has stricter \
* requirements about alignment). \
*/ \
H5MM_memcpy((uint8_t *)dst, &dst_aligned, sizeof(DT)); \
}
/* Macro defining action on destination data which doesn't need to be aligned (after main action) */