diff options
| author | Dana Robinson <43805+derobins@users.noreply.github.com> | 2023-06-03 14:23:35 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2023-06-03 14:23:35 (GMT) |
| commit | e3559c7b64e7963e3515c2ebfd7f1abad810ed19 (patch) | |
| tree | cc2fe52fe08e5b0e5c43e329eaa0fe15b3871b85 /src | |
| parent | 81bc34ac4c3f42532edee32095651f6bcd5e55a2 (diff) | |
| download | hdf5-e3559c7b64e7963e3515c2ebfd7f1abad810ed19.zip hdf5-e3559c7b64e7963e3515c2ebfd7f1abad810ed19.tar.gz hdf5-e3559c7b64e7963e3515c2ebfd7f1abad810ed19.tar.bz2 | |
Add casts to type conversion to fix long dbl bug (#3038)
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.
Diffstat (limited to 'src')
| -rw-r--r-- | src/H5Tconv.c | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/src/H5Tconv.c b/src/H5Tconv.c index 93ca59f..8118eb0 100644 --- a/src/H5Tconv.c +++ b/src/H5Tconv.c @@ -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) */ |