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dwarflint allow strange combinations of attribute/form in gnu mode
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Wed, 30 Mar 2011 12:53:45 +0200
- Subject: dwarflint allow strange combinations of attribute/form in gnu mode
Hi,
I came across a strange combination of new attribute with old form for
gcc. When gcc isn't using -gstrict-dwarf, it allows attributes from
newer versions, but doesn't use new forms, even if such an attribute
would need that. So this patch allows that (in particular for
DW_AT_ranges for dwarf2), but only in gnu mode. Does this look like a
sane solution?
Thanks,
Mark
>From 1872f992638d0d5b15c56c7dcb9a24b7a4b1d9c5 Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mjw@redhat.com>
Date: Wed, 30 Mar 2011 12:44:14 +0200
Subject: [PATCH] dwarflint: Allow DW_AT_ranges with const form, as gnu version 2 extension.
Without -gstrict-dwarf gcc allows usage of attributes from
later versions. One strange case is DW_AT_ranges in version 2
since that version doesn't actually define a rangelistptr
class. This case is added in the form_allowed override for dwarf_gnu,
for version 2. In gnu mode form_allowed checks both variants, source
and extension, in no-gnu mode, only the latest is allowed.
---
dwarflint/dwarf_gnu.cc | 26 ++++++++++++++++++++------
dwarflint/dwarf_gnu.hh | 2 +-
dwarflint/dwarf_version.cc | 22 ++++++++++++++++++----
3 files changed, 39 insertions(+), 11 deletions(-)
diff --git a/dwarflint/dwarf_gnu.cc b/dwarflint/dwarf_gnu.cc
index b70a6d2..6fa50be 100644
--- a/dwarflint/dwarf_gnu.cc
+++ b/dwarflint/dwarf_gnu.cc
@@ -86,13 +86,27 @@ namespace
struct dwarf_gnu_ext_t
: public std_dwarf
{
- dwarf_gnu_ext_t ()
- : std_dwarf (dwarf_gnu_attributes (), form_table ())
- {}
+ unsigned _m_version;
- virtual bool
+ dwarf_gnu_ext_t (unsigned version)
+ : std_dwarf (dwarf_gnu_attributes (), form_table ()),
+ _m_version (version)
+ { }
+
+ bool
form_allowed (attribute const *attr, form const *form) const
{
+ // Without -gstrict-dwarf gcc allows usage of attributes from
+ // later versions. One strange case is DW_AT_ranges in version 2
+ // since that version doesn't actually define a rangelistptr
+ // class. So we just allow data4 or data8 here.
+ if (_m_version == 2 && attr->name () == DW_AT_ranges)
+ {
+ form_width_t width = form->width (NULL);
+ return (form->classes ()[cl_constant]
+ && (width == fw_4 || width == fw_8));
+ }
+
if (attr->name () == DW_AT_GNU_odr_signature)
return form->classes ()[cl_constant] && form->width (NULL) == fw_8;
else
@@ -102,8 +116,8 @@ namespace
}
dwarf_version const *
-dwarf_gnu_ext ()
+dwarf_gnu_ext (unsigned version)
{
- static dwarf_gnu_ext_t dw;
+ static dwarf_gnu_ext_t dw (version);
return &dw;
}
diff --git a/dwarflint/dwarf_gnu.hh b/dwarflint/dwarf_gnu.hh
index dde52f4..14ce31c 100644
--- a/dwarflint/dwarf_gnu.hh
+++ b/dwarflint/dwarf_gnu.hh
@@ -28,6 +28,6 @@
#include "dwarf_version.ii"
-dwarf_version const *dwarf_gnu_ext ();
+dwarf_version const *dwarf_gnu_ext (unsigned version);
#endif//DWARFLINT_DWARF_GNU_HH
diff --git a/dwarflint/dwarf_version.cc b/dwarflint/dwarf_version.cc
index a74e169..6002152 100644
--- a/dwarflint/dwarf_version.cc
+++ b/dwarflint/dwarf_version.cc
@@ -219,6 +219,18 @@ namespace
ret = _m_source->ambiguous_class (form, attribute, candidates);
return ret;
}
+
+ bool
+ form_allowed (attribute const *attr, form const *form) const
+ {
+ // In GNU mode any combination of new attribute/old form goes,
+ // in strict mode only the latest.
+ if (opt_nognu)
+ return _m_extension->form_allowed (attr, form);
+ else
+ return (_m_source->form_allowed (attr, form)
+ || _m_extension->form_allowed (attr, form));
+ }
};
}
@@ -235,7 +247,7 @@ dwarf_version::extend (dwarf_version const *source,
namespace
{
- dwarf_version const *get_ext ()
+ dwarf_version const *get_ext (unsigned version)
{
// xxx The GNU toolchain commonly uses DW_AT_MIPS_linkage_name,
// which is part of the MIPS extensions. So that's what we
@@ -247,31 +259,33 @@ namespace
if (opt_nognu)
return dwarf_mips_ext ();
else
- return dwarf_version::extend (dwarf_mips_ext (), dwarf_gnu_ext ());
+ return dwarf_version::extend (dwarf_mips_ext (),
+ dwarf_gnu_ext (version));
}
}
dwarf_version const *
dwarf_version::get (unsigned version)
{
- static dwarf_version const *ext = get_ext ();
-
switch (version)
{
case 2:
{
+ static dwarf_version const *ext = get_ext (2);
static dwarf_version const *dw = extend (dwarf_2 (), ext);
return dw;
}
case 3:
{
+ static dwarf_version const *ext = get_ext (3);
static dwarf_version const *dw = extend (dwarf_3 (), ext);
return dw;
}
case 4:
{
+ static dwarf_version const *ext = get_ext (4);
static dwarf_version const *dw = extend (dwarf_4 (), ext);
return dw;
}
--
1.7.4