Kingsly John <[EMAIL PROTECTED]> writes:
> Can someone explain what bus error is ? I have seen this happen on
> my machine when I try to pipe large amounts of data or
> something... but then on a second try it normally works fine!
>
> Kingsly
Here is an excerpt from Peter Van Der Linden's excellent "Expert C
Programming" book:
/----
| ...Most of the the problem lies in the fact that the errors represent
| an anomaly the operating system has detected, and the anomaly is
| reported in terms most convenient to the operating system. The
| precise causes of a bus error and a segmentation fault will thus vary
| among different versions of operating systems...
|
| In practice, a bus error is almost always caused by a misaligned read
| or write. It's called a bus error, because the address bus is the
| component that chokes if a misaligned load or store is requested.
| Alignment means that data items can only be stored at an address that
| is a multiple of their size. On modern architectures, especially RISC
| architectures, data alignment is required because extra logic
| associated with arbitrary alignment makes the whole memory system much
| larger and slower...
|
| ...A few years ago bus errors were also generated if a memory parity
| error was detected. These days memory chips are so reliable, and so
| well protected y error detection and correction circuitry, that parity
| erors are almost unheard of at the application programming level. A
| bus error can also be generated by referencing memory that does not
| physically exist; you probably won't be able to screw up this badly
| without help from a naughty device driver.
\----
The book was published in 1994 by SunSoft Press.
-karra
--
All's well that ends.
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