On 23/08/12 21:27, Alasdair G Kergon wrote:
On Thu, Aug 23, 2012 at 02:31:02PM +0100, Matthew Booth wrote:
- if (sscanf(ptr, "%llu %llu %s %n",
- &start, &size, ttype, &n) < 3) {
+ if (sscanf(ptr, "%llu %llu %s %n", &start, &size, ttype, &n) != 4) {
Did you test this?
No. My git-fu isn't good enough to point that out in the email without
cluttering the commit message with it, but I pointed it out on IRC.
According to the sscanf man page:
n Nothing is expected; instead, the number of characters consumed
thus far from the input is stored through the next pointer,
which must be a pointer to int. This is not a conversion,
although it can be suppressed with the * assignment-suppression
character. The C standard says: "Execution of a %n directive
does not increment the assignment count returned at the comple-
tion of execution" but the Corrigendum seems to contradict this.
Probably it is wise not to make any assumptions on the effect of
%n conversions on the return value.
Thanks for being thorough. I've now made another entry in my mental list
of surprising interfaces :)
Matt
--
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team
GPG ID: D33C3490
GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490
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