R on Solaris 10 x64

Hmm, and can you see "both ends" of tgath_buf and buf (in particular 
tgath_but[curr_len - 1] and buf[curr_len-1])?

(dbx) p tgath_buf[curr_len - 1]
tgath_buf[curr_len-1] = '\0'
(dbx) p buf[curr_len-1]
dbx: cannot access address 0x9f7f6ff
(dbx) p tgath_buf[curr_len - 2]
tgath_buf[curr_len-2] = '\0'
(dbx) p buf[curr_len-2]
dbx: cannot access address 0x9f7f6fe
(dbx)

Something is definitely wrong with this memcpy() operation. I 
suppose we'll need some help from the HDF5 folks to figure out 
what the buf memory buffer is supposed contain in this case.

If only to "eliminate from our inquiries", I'd try running CPP over the 
code and see if the full macro expansion (including that from memcpy to 
_memcpy) is working as intended.

After the macro expansion, this code looks like this:

         for(curr_seq=0; curr_seq<nseq; curr_seq++) {
             curr_len=len[curr_seq];
              memcpy ( ( char * ) ( tgath_buf ) , ( const char * 
) ( buf + off [curr_seq ] ) , curr_len );
             tgath_buf+=curr_len;
         }

I take it that you've already tried compiling the module at maximal 
warning level?

No. We can try that, as well as lint.

Thanks.

-Greg