Dwarves Archive on lore.kernel.org
 help / color / Atom feed
From: Zack Weinberg <zweinberg-4eJtQOnFJqFBDgjK7y7TUQ@public.gmane.org>
To: "Ilpo Järvinen" <ilpo.jarvinen-pxSi+dnQzZMxHbG02/KK1g@public.gmane.org>
Cc: Arnaldo Carvalho de Melo
	<acme-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	dwarves-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: Formatting "drivers" was Re: Can't persuade pahole to see through forward declarations
Date: Tue, 23 Jun 2009 23:40:18 -0700
Message-ID: <20090623234018.61f1ce02@mozilla.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0906240918170.26611-tOJ5Hk0ALFH+1EwMtL+0ZheBoQapMCRCVQQcQy+6Uvc@public.gmane.org>

"Ilpo Järvinen" <ilpo.jarvinen-pxSi+dnQzZMxHbG02/KK1g@public.gmane.org> wrote:
> On Thu, 18 Jun 2009, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Jun 18, 2009 at 01:28:20PM -0700, Zack Weinberg escreveu:
> > >  - You do not have to process C declaration syntax to find the
> > > name of each field.
> 
> Good point, this is one of the most complex tasks in scripts to get 
> general case right. Besides typedefs, especially those function
> pointers which appear in return value and arguments make it a task
> too hairy for any sane people, not that I'd say it is
> impossible... :-)

I used to hack gcc.  I know *exactly* how hard it is to parse C
declarations. :-)

I had been doing okay, for the limited thing I am trying to do, with
sed scripts to munge the pahole output into something that could be
relatively easily parsed by a Python script, but then I ran into this
construct:

  struct S {
    ...
    struct T {
      int a;
    } tee[2];
  };

No hint that there are two copies of T embedded in S, here, until it's
far too late to do anything about it (if you're a sed script).

> > >  - There is never missing data; in many cases pahole currently
> > > will omit the offset in its annotation of a full nested structure,
> > >    for instance, which is fine for humans but really bad for
> > > machine processing.
> > 
> > Annoying "simplification", I'll put the offset there explicitely,
> > just worried that Ilpo may be using it in his sed scripts... Ilpo?
> 
> No, I'm not. I usually try to avoid trusting such things anyway,
> unless I really have to. You just don't parse anything c-like with
> newlines / spaces as significant :-).

I actually have a patch for this one now :-)  I looked harder at my
data set and realized it only happens with unions.  There's also a 
small typo fix in here, I was getting "classnsThing *" a lot...

diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
index e3e621f..bbc5dd6 100644
--- a/dwarves_fprintf.c
+++ b/dwarves_fprintf.c
@@ -319,7 +319,7 @@ static const char *tag__prefix(const struct cu *cu, const uint32_t tag)
 	case DW_TAG_structure_type:
 		return cu->language == DW_LANG_C_plus_plus ? "class " :
 							     "struct ";
-	case DW_TAG_class_type:		return "class";
+	case DW_TAG_class_type:		return "class ";
 	case DW_TAG_union_type:		return "union ";
 	case DW_TAG_pointer_type:	return " *";
 	case DW_TAG_reference_type:	return " &";
@@ -679,6 +679,7 @@ static size_t union_member__fprintf(struct class_member *self,
 				    const struct conf_fprintf *conf, FILE *fp)
 {
 	const size_t size = self->byte_size;
+	const size_t offset = conf->base_offset;
 	size_t printed = type__fprintf(type, cu, s(cu, self->name), conf, fp);
 
 	if ((tag__is_union(type) || tag__is_struct(type) ||
@@ -693,17 +694,17 @@ static size_t union_member__fprintf(struct class_member *self,
 			 * '} member_name;' last line of the type printed in the
 			 * above call to type__fprintf.
 			 */
-			printed += fprintf(fp, ";%*s/* %11zd */",
+			printed += fprintf(fp, ";%*s/* %5zd %5zd */",
 					   (conf->type_spacing +
-					    conf->name_spacing - slen - 3), " ", size);
+					    conf->name_spacing - slen - 3), " ", offset, size);
 		}
 	} else {
 		printed += fprintf(fp, ";");
 
 		if (!conf->suppress_offset_comment) {
 			const int spacing = conf->type_spacing + conf->name_spacing - printed;
-			printed += fprintf(fp, "%*s/* %11zd */",
-					   spacing > 0 ? spacing : 0, " ", size);
+			printed += fprintf(fp, "%*s/* %5zd %5zd */",
+					   spacing > 0 ? spacing : 0, " ", offset, size);
 		}
 	}
 
--
To unsubscribe from this list: send the line "unsubscribe dwarves" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20090615172409.6f0f322b@mozilla.com>
     [not found] ` <20090617170217.GB21530@ghostprotocols.net>
     [not found]   ` <20090617170217.GB21530-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2009-06-17 17:25     ` Zack Weinberg
     [not found]       ` <20090617102506.34aaf8e2-4eJtQOnFJqFBDgjK7y7TUQ@public.gmane.org>
2009-06-17 20:56         ` Arnaldo Carvalho de Melo
2009-06-18 18:36         ` Arnaldo Carvalho de Melo
     [not found]           ` <20090618183634.GE21530-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2009-06-18 20:28             ` Zack Weinberg
     [not found]               ` <20090618132820.2eb7371a-4eJtQOnFJqFBDgjK7y7TUQ@public.gmane.org>
2009-06-18 20:50                 ` Formatting "drivers" was " Arnaldo Carvalho de Melo
     [not found]                   ` <20090618205053.GA4258-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2009-06-24  6:29                     ` Ilpo Järvinen
     [not found]                       ` <Pine.LNX.4.64.0906240918170.26611-tOJ5Hk0ALFH+1EwMtL+0ZheBoQapMCRCVQQcQy+6Uvc@public.gmane.org>
2009-06-24  6:40                         ` Zack Weinberg [this message]
     [not found]                           ` <20090623234018.61f1ce02-4eJtQOnFJqFBDgjK7y7TUQ@public.gmane.org>
2009-06-24  6:58                             ` Ilpo Järvinen
2009-06-24  6:42                     ` Zack Weinberg

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20090623234018.61f1ce02@mozilla.com \
    --to=zweinberg-4ejtqonfjqfbdgjk7y7tuq@public.gmane.org \
    --cc=acme-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
    --cc=dwarves-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=ilpo.jarvinen-pxSi+dnQzZMxHbG02/KK1g@public.gmane.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Dwarves Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dwarves/0 dwarves/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dwarves dwarves/ https://lore.kernel.org/dwarves \
		dwarves@vger.kernel.org
	public-inbox-index dwarves

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.dwarves


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git