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Re: [PATCH] readelf: Handle signedness of DW_FORM_implicit_const and DW_AT_const_value.
- From: Mark Wielaard <mark at klomp dot org>
- To: elfutils-devel at sourceware dot org
- Date: Sat, 16 Jun 2018 00:17:35 +0200
- Subject: Re: [PATCH] readelf: Handle signedness of DW_FORM_implicit_const and DW_AT_const_value.
- References: <1528894303-31189-1-git-send-email-mark@klomp.org>
On Wed, Jun 13, 2018 at 02:51:43PM +0200, Mark Wielaard wrote:
> We only handles DW_FORM_sdata as a signed form, but DW_FORM_implicit_const
> is also signed by default. For DW_AT_const_value we can do a little better.
> GCC encodes some const_values with signed forms, even though the type
> is unsigned. Lookup the (base) type of the DIE and display the const value
> as their (signed) type/size (if we can determine that).
>
> Add a new testcase run-readelf-const-values.sh that shows that.
> With the new testcase the const values would come out as follows:
>
> name (string) "i"
> const_value (implicit_const) 18446744073709551615
> name (string) "j"
> const_value (implicit_const) 18446744073709551615
>
> name (string) "sc"
> const_value (sdata) -2
> name (string) "uc"
> const_value (sdata) -2
> name (string) "ss"
> const_value (sdata) -16
> name (string) "us"
> const_value (sdata) -16
> name (string) "si"
> const_value (sdata) -3
> name (string) "ui"
> const_value (sdata) -94967296
> name (string) "sl"
> const_value (sdata) -1
> name (string) "ul"
> const_value (sdata) -1
>
> With this patch they show up as:
>
> name (string) "i"
> const_value (implicit_const) -1
> name (string) "j"
> const_value (implicit_const) -1
>
> name (string) "sc"
> const_value (sdata) -2
> name (string) "uc"
> const_value (sdata) 254 (-2)
> name (string) "ss"
> const_value (sdata) -16
> name (string) "us"
> const_value (sdata) 65520 (-16)
> name (string) "si"
> const_value (sdata) -3
> name (string) "ui"
> const_value (sdata) 4200000000 (-94967296)
> name (string) "sl"
> const_value (sdata) -1
> name (string) "ul"
> const_value (sdata) 18446744073709551615 (-1)
>
> (for signed/unsigned int char, short and long)
Pushed to master.