linux-kernel - Re: [PATCH] Fix segfault in dtc when empty input file is given.

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Date:	Tue, 25 Sep 2012 09:44:31 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Markus Mayer <mmayer@...adcom.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix segfault in dtc when empty input file is given.

On 09/14/2012 04:23 PM, Markus Mayer wrote:
> Prior to this change, an empty input file would cause a segfault, because
> yylloc had never been initialized. There was never any characters for the
> lexer to match, so YY_USER_ACTION was never executed before the parse error
> was detected.
> 
> When the parser printed the error message, it tried to include the name of
> the file, but the structure holding the file name (yylloc.file, referenced
> as pos->file) had never been initialized.

> diff --git a/scripts/dtc/treesource.c b/scripts/dtc/treesource.c

>  struct boot_info *dt_from_source(const char *fname)
>  {
> +	extern YYLTYPE yylloc;
> +
>  	the_boot_info = NULL;
>  	treesource_error = 0;
>  
>  	srcfile_push(fname);
>  	yyin = current_srcfile->f;
> +	/* Initialize yylloc->file to avoid segfault on empty input */
> +	srcpos_update(&yylloc, NULL, 0);

Wouldn't srcpos_update(&yyloc, fname, 0); be even more informative?

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