BUG: Use memcpy instead of casting to over-aligned pointer types - #116
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19 -Wcast-align warnings, and behind them undefined behavior on any
target that cares about alignment.
modify_field() writes a value into a header field at a byte offset
parsed from a field table:
((short *)((char *)basep + field->offset))[fc] = (short)val;
field->offset is a byte offset into a packed on-disk header, so that
cast produces an address only correctly aligned by coincidence. The
same pattern appears for int, int64_t, float and double, in both tool
files. Each becomes a memcpy of the right width at the right byte
offset.
The second group reads a pointer back out of a structure through a
byte offset -- `sp = *(char **)((char *)str + fp->offset)` and the
nifti1_extension equivalents -- and becomes a memcpy into an aligned
local.
The third is nifti_header_version(), which cast its `const char * buf`
argument, a buffer straight off a file read with no alignment
guarantee, to both nifti_1_header * and nifti_2_header * and read
fields through them. It now copies into aligned locals first, exactly
the sizeof(nifti_1_header) bytes the function already checks are
present.
Verified by round-tripping int16, int32, int64, float32, float64 and
string fields through nifti_tool -mod_hdr2.
(cherry picked from commit eb4f831)
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Re-submission of #44, reverted from
masteron 2026-09-24 so it can bereviewed before merging. Content is unchanged from the original.
Base:
master. Independent: nothing has to land before it.Commits
Ordering for all the re-submitted work is tracked in #84.