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

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Subject: [Xen-devel] [PATCH] libxl: correctly initialise yylineno
From: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Date: Wed, 2 Mar 2011 14:35:44 +0000
Cc: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Delivery-date: Wed, 02 Mar 2011 06:37:09 -0800
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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>
 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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