[RFA] initialize err variable in load_section_callback()
Tue Oct 26 00:04:00 GMT 2004
Theodore A. Roth wrote:
> On Wed, 20 Oct 2004, Andrew Cagney wrote:
>>Theodore A. Roth wrote:
>>>I just encountered a problem with using the "load" command with a remote
>>>avr target. The first packet would be sent to the remote target and then
>>>gdb would just give up with this error message:
>>> (gdb) load
>>> Loading section .text, size 0x1f8 lma 0x0
>>> Sending packet: $M0,a:0c9446000c9463000c94#d7...Ack
>>> Packet received: OK
>>> Memory access error while loading section .text.
>>>It looks like load_section_callback() in symfile.c is assuming that a
>>>call to target_write_memory_partial() will set the err variable.
>>>Unfortunately, that is not a valid assumption.
>>>The attached patch got things working again, but this feels like a hack
>>>to me since target_write_memory_partial() should really be setting err
>>>to a sane value before returning.
>>>Patch is against today's cvs mainline.
>>Here's the contract:
>>/* Make a single attempt at transfering LEN bytes. On a successful
>> transfer, the number of bytes actually transfered is returned and
>> ERR is set to 0. When a transfer fails, -1 is returned (the number
>> of bytes actually transfered is not defined) and ERR is set to a
>> non-zero error indication. */
>>So the bug is further down the target stack.
> Both target_write_memory_partial() and target_read_memory_partial()
> break that contract then:
> target_write_memory_partial (CORE_ADDR memaddr, char *buf, int len, int *err)
> if (target_xfer_partial_p ())
> return target_xfer_partial (target_stack, TARGET_OBJECT_MEMORY, NULL,
> NULL, buf, memaddr, len);
> return target_xfer_memory_partial (memaddr, buf, len, 1, err);
> If target_xfer_partial_p() returns true (which the avr port does), then
> err is never set and the caller will see garbage if it didn't initialize
> Should the return value of the target_xfer_partial() call be checked, or
> should err just be blindly see to zero?
The result will need to be checked, and *err set accordingly.
Hmm, to_xfer_partial doesn't specify how to handle errors. We'd better
pin that down.
Of hand the interface could allow:
- when -1, set *err to errno
- when -1, set *err to EIO
- when -ve, set *err -VE return value
I suspect that it should be the first. The comments for
target_read_partial should also be updated to mention this.
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