[gdb/build] Fix build with g++-4.8

When building g++-4.8, we run into:
...
src/gdb/dwarf2/read.c:919:5: error: multiple fields in union \
  'partial_die_info::<anonymous union>' initialized
...

This is due to:
...
    union
    {
      struct
      {
       CORE_ADDR lowpc = 0;
       CORE_ADDR highpc = 0;
      };
      ULONGEST ranges_offset;
    };
...

The error looks incorrect, given that only one union member is initialized,
and does not reproduce with newer g++.

Nevertheless, work around this by moving the initialization to a constructor.

[ I considered just removing the initialization, with the idea that access
should be guarded by has_pc_info, but I ran into one failure in the testsuite,
for gdb.base/check-psymtab.exp due to add_partial_symbol using lowpc without
checking has_pc_info. ]

Tested on x86_64-linux.

1 files changed, 6 insertions, 2 deletions

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index d2501c9..00aa64d 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -920,8 +920,8 @@ struct partial_die_info : public allocate_on_obstack
       /* If HAS_PC_INFO, the PC range associated with this DIE.  */
       struct
       {
-	CORE_ADDR lowpc = 0;
-	CORE_ADDR highpc = 0;
+	CORE_ADDR lowpc;
+	CORE_ADDR highpc;
       };
       /* If HAS_RANGE_INFO, the ranges offset associated with this DIE.  */
       ULONGEST ranges_offset;
@@ -974,6 +974,10 @@ struct partial_die_info : public allocate_on_obstack
       is_dwz = 0;
       spec_is_dwz = 0;
       canonical_name = 0;
+      /* Don't set these using NSDMI (Non-static data member initialisation),
+	 because g++-4.8 will error out.  */
+      lowpc = 0;
+      highpc = 0;
     }
   };