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Re: BUG: alternatives
On Sun, Nov 06, 2005 at 01:52:14PM -0500, Charles Wilson wrote:
>Christopher Faylor wrote:
>
>>A signal shouldn't cause a truncated read when retrieving data from
>>disk on cygwin or linux.
>
>ACK.
>
>>I think the only sane way to handle this is to put the read in a loop
>>and realloc the buffer as needed as long as the read continues to return
>>'>0'.
>
>Ok.
>
>>It's obviously pretty racy to get the size of the file and then expect that
>>you'll be able to read in exactly that many bytes.
>
>ACK.
>
>Revised patch attached. I'm wondering, tho, about the advisability of
>using alloca'ed (rather than malloc'ed) memory to hold the contents of a
>file of unrestricted size. Aren't there limits on the available space
>within a single stack frame? Does it make sense (is it legal) to alloca
>40k or 50k or 500k? of memory?
>
>Granted, most /var/lib/alternatives files are going to be fairly small
>(< 1k) but there's no guarantee of that...
I have mixed feelings about alloca, personally. I use it all of the time but
it is always with some trepidation because, AFAIK, the failure condition for
alloca is a SEGV. OTOH, it is very convenient.
In this case, however, I think you really want to use realloc. You could even
rely on the fact that realloc(NULL, n) is equivalent to malloc(n).
cgf
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