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Re: [libvirt] [PATCH 2/4] Update modified mac address in place in virGetInterface



On 07/22/2009 11:36 AM, Daniel P. Berrange wrote:
On Wed, Jul 22, 2009 at 11:25:38AM -0400, Laine Stump wrote:
On 07/22/2009 10:20 AM, Daniel Veillard wrote:
Agreed, patch applied, I only had to add _() to get the message localized,
I've idly wondered about that macro, as it causes scores of compile warnings, like this:

datatypes.c:291: warning: format not a string literal and no format arguments

What's it for? And what's the best way to change things to eliminate the warnings?

It is a potential security hole, if the user finds a way to send a string
with an embeded format specifier. Thus if you're not doing any subsitutions,
and the string isn't constant, then you should always at least do

  char *therealstring = ...from somewhere untrusted...
  printf("%s", therealstring)

Yeah, I understand the perils of using a non-literal string as the format to *printf(). I'm wondering what the purpose of _() is, and why it causes the compiler to believe the string isn't a literal. (I received this warning when others don't because I use "-Wformat -Wformat-security" in my CFLAGS, at Jim's suggestion).

NB, anyone sending patches should always set

   --enable-compile-warnings=error

when running 'autogen.sh' and make sure all warnings & errors are fixed before submitting a patch.

It's actually because I like doing this that I'd like to know the preferred method of eliminating the warnings I mentioned. There are a bunch of them pre-existing in the code that I want to get rid of so I can turn on warnings=error (without turning off these warnings in CFLAGS), and I want to do it the "accepted" way. For example, from domain_conf.c:2137:

virDomainReportError(conn, VIR_ERR_XML_ERROR,
_("invalid security type"));

spits out the warning. We all know that it really *is* literal, but the macro is changing the class so the compile thinks it isn't. It would be simple to just change it to:

virDomainReportError(conn, VIR_ERR_XML_ERROR,
"%s", _("invalid security type"));

(and there are plenty of those too), but that's inefficient, and doesn't do the _() around the "%s" (is that correct or not?).

If someone wants to tell me the preferred way of doing these, I'll handle the grunt work of making the changes.


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