parchive

The attached patch corrects an alignment problem on
SPARC processors. The original version may access
i64 values that are not aligned at 8 byte
boundaries if the value of ptr is not a multiple of
8 in read_pfile. On a SPARC (and probably HP-PA
and Alpha as well), unaligned access triggers a
segmentation violation.

-- mva



--- rwpar.c.orig Sat Nov 17 21:20:09 2001
+++ rwpar.c Thu Nov 29 02:21:15 2001
@@ -225,21 +225,20 @@
read_pfile(pfile_t *file, u8 *ptr, u16 *path, i64 pl)
{
i64 i, l;
- pfile_entr_t *pf;
-
- pf = ((pfile_entr_t *)ptr);
-
- i = read_i64(&pf->size);
- file->status = read_i64(&pf->status);
- file->file_size = read_i64(&pf->file_size);
- COPY(file->hash, pf->hash, sizeof(md5));
- COPY(file->hash_16k, pf->hash_16k, sizeof(md5));
+ pfile_entr_t pf;
+
+ COPY(&pf, ptr, 1);
+ i = read_i64(&pf.size);
+ file->status = read_i64(&pf.status);
+ file->file_size = read_i64(&pf.file_size);
+ COPY(file->hash, pf.hash, sizeof(md5));
+ COPY(file->hash_16k, pf.hash_16k, sizeof(md5));
l = (i - FILE_ENTRY_FIX_SIZE) / 2;
NEW(file->filename, pl + l + 1);
COPY(file->filename, path, pl);
- read_u16s(file->filename + pl, &pf->filename, l);
+ read_u16s(file->filename + pl, &pf.filename, l);
file->filename[l + pl] = 0;
-
+ COPY(ptr, &pf, 1);
return i;
}

Sorry,

the patch has only 2 errors :-/ Forget it.

On closer inspection, I don't know why it works
slightly better on this SunOS 5.6 box. And I don't
know at all why the original version breaks. Back
to the debugger...

-- mva

Another attempt:

--- rwpar.c.orig Sat Nov 17 21:20:09 2001
+++ rwpar.c Thu Nov 29 04:32:20 2001
@@ -232,8 +232,8 @@
i = read_i64(&pf->size);
file->status = read_i64(&pf->status);
file->file_size = read_i64(&pf->file_size);
- COPY(file->hash, pf->hash, sizeof(md5));
- COPY(file->hash_16k, pf->hash_16k, sizeof(md5));
+ memmove(file->hash, pf->hash, sizeof(md5));
+ memmove(file->hash_16k, pf->hash_16k, sizeof(md5));
l = (i - FILE_ENTRY_FIX_SIZE) / 2;
NEW(file->filename, pl + l + 1);
COPY(file->filename, path, pl);

Would anybody venture a guess why using memcpy
instead of memmove gets me a bus error if ptr%8!=0?
This is SunOS 5.6 using gcc 2.95.2 on a SPARC.

The memmove variant works fine. IMO, memcpy should
work indepedent of alignment. Maybe gcc tries to
be clever, but gets its optimization wrong.

-- mva