[PATCH] chg: check snprintf result strictly

[Augie Fackler]

On Wed, Jan 11, 2017 at 11:42:57PM +0800, Jun Wu wrote:
> # HG changeset patch
> # User Jun Wu <quark at fb.com>
> # Date 1484149164 -28800
> #      Wed Jan 11 23:39:24 2017 +0800
> # Node ID 5cbdc769201b22cbc4f698c7bc9235984c7cf427
> # Parent  e882c7bb5a0ba2589a44108c9a87b300a13e08df
> # Available At https://bitbucket.org/quark-zju/hg-draft
> #              hg pull https://bitbucket.org/quark-zju/hg-draft -r 5cbdc769201b
> chg: check snprintf result strictly

Queued, thanks

>
> This makes the program more robust when somebody changes hgclient's
> maxdatasize in the future.
>
> diff --git a/contrib/chg/hgclient.c b/contrib/chg/hgclient.c
> --- a/contrib/chg/hgclient.c
> +++ b/contrib/chg/hgclient.c
> @@ -367,7 +367,9 @@ static void readhello(hgclient_t *hgc)
>  static void updateprocname(hgclient_t *hgc)
>  {
> -	size_t n = (size_t)snprintf(hgc->ctx.data, hgc->ctx.maxdatasize,
> +	int r = snprintf(hgc->ctx.data, hgc->ctx.maxdatasize,
>                       "chg[worker/%d]", (int)getpid());
> -	hgc->ctx.datasize = n;
> +	if (r < 0 || (size_t)r >= hgc->ctx.maxdatasize)
> +		abortmsg("insufficient buffer to write procname (r = %d)", r);
> +	hgc->ctx.datasize = (size_t)r;
>       writeblockrequest(hgc, "setprocname");
>  }
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