R devel - Apr 2016 - [PATCH] fix CHECK_this_length in sprintf.c

All~

CHECK_this_length macro expands to multiple statements making it unsafe to
use in a single line `if` statement (as is happening near line 335).  This
fixes the macro using the standard `do { } while (0)` macro trick.

Matt
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>>>>> Matthew Fowles Kulukundis <matt.fowles at gmail.com>
>>>>>     on Tue, 5 Apr 2016 11:17:30 -0400 writes:
    > All~
    > CHECK_this_length macro expands to multiple statements making it unsafe
to
    > use in a single line `if` statement (as is happening near line 335). 
This
    > fixes the macro using the standard `do { } while (0)` macro trick.

yes, but you forgot the closing '}' ... so you could not even
have compiled R after applying your patch.  

Also, it would be nice to contrive a minimal example where the
change makes a difference.  This  "fails" to trigger :

--------------------------------
as.double.foo <- function(x) x[FALSE]
x <- structure(3, class="foo")
as.numeric(x) # numeric(0)

sprintf("%d !", x)# "3 !"  instead of giving an error
--------------------------------

Thank you, Matt, in any case; this (with the "{" !) has now gone
into the source.

Martin

    > Matt
    > x[DELETED ATTACHMENT external: r-sprintf.patch, text/x-patch]
    > ______________________________________________
    > R-devel at r-project.org mailing list
    > https://stat.ethz.ch/mailman/listinfo/r-devel

Martin~

Sorry about the bad patch.  I work on C++ at Google. We built a check for
clang-tidy that identifies errors of this form and discovered the error
here as part of our search. I am just trying to be a good citizen and
upstream a fix, but I must have gotten sloppy as I was doing a bunch of
these.

Thanks for fixing it and finding the a test for it, I actually had no idea
how to trigger this codepath and have never used R.

If you are curious, the upstream check for clang-tidy is
http://reviews.llvm.org/D18766
You may consider running some of the other clang-tidy checks on your source
base, they will likely find other bugs.

Cheers,
Matt

On Thu, Apr 7, 2016 at 6:46 AM, Martin Maechler <maechler at
stat.math.ethz.ch>
wrote:
> >>>>> Matthew Fowles Kulukundis <matt.fowles at
gmail.com>
> >>>>>     on Tue, 5 Apr 2016 11:17:30 -0400 writes:
>
>     > All~
>     > CHECK_this_length macro expands to multiple statements making it
> unsafe to
>     > use in a single line `if` statement (as is happening near line
> 335).  This
>     > fixes the macro using the standard `do { } while (0)` macro trick.
>
> yes, but you forgot the closing '}' ... so you could not even
> have compiled R after applying your patch.
>
> Also, it would be nice to contrive a minimal example where the
> change makes a difference.  This  "fails" to trigger :
>
> --------------------------------
> as.double.foo <- function(x) x[FALSE]
> x <- structure(3, class="foo")
> as.numeric(x) # numeric(0)
>
> sprintf("%d !", x)# "3 !"  instead of giving an error
> --------------------------------
>
> Thank you, Matt, in any case; this (with the "{" !) has now gone
> into the source.
>
> Martin
>
>     > Matt
>     > x[DELETED ATTACHMENT external: r-sprintf.patch, text/x-patch]
>     > ______________________________________________
>     > R-devel at r-project.org mailing list
>     > https://stat.ethz.ch/mailman/listinfo/r-devel
>
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