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Re: [Xen-devel] [PATCH] libxl: correctly initialise yylineno

To: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] libxl: correctly initialise yylineno
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Wed, 2 Mar 2011 17:16:41 +0000
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On Wed, 2011-03-02 at 14:35 +0000, Ian Jackson wrote:
> Sometimes xl would read an uninitialised variable when printing error
> messages, resulting in things like this:
>   /etc/xen/thing.cfg:1030057088: config parsing error near `"ws08r2-x64-2': 
> lexical error
> This is because yylineno is a variable inside the scanner created by
> yylex_init, but it is not initialised by yylex_init.
> (Debian bug #616099.)
> On the way I discovered a lot of complication to do with the calling
> convention between bison and flex in reentrant parsers/scanners which
> use locations (Debian bug #616100) but as the above change makes the
> current code in xen-unstable work I don't propose to do anything else
> about that now in our tree.
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>

This fixes the issue I was having:

        # xl cr -d /root/x
        Parsing config file /root/x
        /root/x:24: config parsing error near `"ws08r2-x64-2': lexical error
        Failed to parse config file: Invalid argument

Where line 24 does indeed contain an error.

Tested/Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> ---
>  tools/libxl/libxlu_cfg.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> diff --git a/tools/libxl/libxlu_cfg.c b/tools/libxl/libxlu_cfg.c
> index 663fdf9..f947c21 100644
> --- a/tools/libxl/libxlu_cfg.c
> +++ b/tools/libxl/libxlu_cfg.c
> @@ -43,6 +43,9 @@ static void ctx_dispose(CfgParseContext *ctx) {
>  static void parse(CfgParseContext *ctx) {
>      /* On return, ctx.err will be updated with the error status. */
>      int r;
> +
> +    xlu__cfg_yyset_lineno(1, ctx->scanner);
> +
>      r= xlu__cfg_yyparse(ctx);
>      if (r) assert(ctx->err);

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