[patch] DWARF-3+ DW_AT_accessibility defaults #2 (GCC PR debug/45124)

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

this is a repost for:
	[patch] Fix DWARF-3+ DW_AT_accessibility default assumption
	http://sourceware.org/ml/gdb-patches/2011-01/msg00507.html
	Re: [patch] Fix DWARF-3+ DW_AT_accessibility default assumption
	http://sourceware.org/ml/gdb-patches/2011-03/msg00546.html
	revert: Re: [patch] Fix DWARF-3+ DW_AT_accessibility default assumption
	http://sourceware.org/ml/gdb-patches/2011-03/msg00586.html

	     FSF GDB HEAD:    former patch:    this patch:
	        dw-2 dw-3        dw-2 dw-3        dw-2 dw-3
	gcc-4.5 pass pass    4.5 pass FAIL    4.5 pass pass
	gcc-4.6 pass FAIL    4.6 pass pass    4.6 pass pass

	(set -x;for gcc in 45 46;do for dwarf in 2 3;do PATH="/your-gcc-dir/gcc${gcc}-root/bin:$PATH" runtest CXX_FOR_TARGET="g++ -gdwarf-${dwarf}" gdb.cp/casts.exp gdb.cp/classes.exp gdb.cp/virtfunc.exp gdb.mi/gdb792.exp gdb.python/py-value.exp ;done;done)

Normally it probably is not of much concern as FSF GCC defaults to -gdwarf-2
where no changes happen.  Just Fedoras+RHELs default to -gdwarf-3 where the
assumed defaults have changed, therefore proposing for FSF GDB to verify
DW_AT_producer - it affects even FSF GCCs when one uses -gdwarf-3 or -gdwarf-4.

Due to the mess I did before waiting for a review.  I believe this fix should
be a gdb-7.3 blocker as gcc-4.6.0 will be released far before gdb-7.4.

I do not provide a special new testcase as the testcases already exist and a
gdb.dwarf2/ code would just carbon-copy the conditionals while it is more
important the conditionals match the real compilers behavior.


Thanks,
Jan


(set -ex;echo 'class C { public: int priv; } c;' | g++ -gdwarf-3 -c -g -o 1.o -x c++ -; readelf -wi 1.o)
old = no DW_AT_accessibility
new = DW_AT_accessibility: 1 (public)
old gcc-4.4.5-6.el6.x86_64     = GNU C++ 4.4.5 20110214 (Red Hat 4.4.5-6)    
old gcc-4.5.1-4.fc14.x86_64    = GNU C++ 4.5.1 20100924 (Red Hat 4.5.1-4)
new gcc-4.6.0-0.14.fc15.x86_64 = GNU C++ 4.6.0 20110318 (Red Hat 4.6.0-0.14)    
new GNU C++ 4.7.0 20110321 (experimental)    
new GNU C++ 4.6.0 20110321 (prerelease) 
old GNU C++ 4.5.3 20110321 (prerelease) 
XXX GNU C++ 4.4.6 20110321 (prerelease) [-gdwarf-3 not supported]


gdb/
2011-03-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* dwarf2read.c (producer_is_gxx_lt_4_6): New function.
	(dwarf2_add_field): Fix new_field->accessibility for
	cu->header.version >= 3 while verifying also producer_is_gxx_lt_4_6.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -6209,6 +6209,27 @@ dwarf2_record_block_ranges (struct die_info *die, struct block *block,
     }
 }
 
+/* Check for GCC PR debug/45124 fix which is not present in any G++ version up
+   to 4.5.any hwile it is present already in G++ 4.6.0 - the PR has been fixed
+   during 4.6.0 experimental.  */
+
+static int
+producer_is_gxx_lt_4_6 (const char *producer)
+{
+  int major, minor;
+
+  /* Whitespaces are ignored in both PRODUCER and the format string.  */
+  if (sscanf (producer, "GNU C++ %d.%d", &major, &minor) != 2)
+    {
+      /* For non-GCC compilers expect their behavior is DWARF version
+	 compliant.  */
+
+      return 0;
+    }
+
+  return major < 4 || (major == 4 && minor < 6);
+}
+
 /* Add an aggregate field to the field list.  */
 
 static void
@@ -6239,13 +6260,28 @@ dwarf2_add_field (struct field_info *fip, struct die_info *die,
     }
   fip->nfields++;
 
-  /* Handle accessibility and virtuality of field.
-     The default accessibility for members is public, the default
-     accessibility for inheritance is private.  */
-  if (die->tag != DW_TAG_inheritance)
-    new_field->accessibility = DW_ACCESS_public;
+  if (cu->header.version < 3 || producer_is_gxx_lt_4_6 (cu->producer))
+    {
+      /* The default DWARF 2 accessibility for members is public, the default
+	 accessibility for inheritance is private.  */
+
+      if (die->tag != DW_TAG_inheritance)
+	new_field->accessibility = DW_ACCESS_public;
+      else
+	new_field->accessibility = DW_ACCESS_private;
+    }
   else
-    new_field->accessibility = DW_ACCESS_private;
+    {
+      /* DWARF 3+ defines the default accessibility a different way - see
+	 below - than DWARF 2 has defined.  The same rules apply now for
+	 DW_TAG_inheritance as for the members and it only depends on the
+	 container kind.  */
+
+      if (die->parent->tag == DW_TAG_class_type)
+	new_field->accessibility = DW_ACCESS_private;
+      else
+	new_field->accessibility = DW_ACCESS_public;
+    }
   new_field->virtuality = DW_VIRTUALITY_none;
 
   attr = dwarf2_attr (die, DW_AT_accessibility, cu);