Fix dwarf2_name caching bug

PR gdb/25663 points out that dwarf2_name will cache a value in the
bcache and then return a substring.  However, this substring return is
only done on the branch that caches the value -- so if the function is
called twice with the same arguments, it will return different values.

This patch fixes this problem.

This area is strange.  We cache the entire demangled string, but only
return the suffix.  I looked at caching just the suffix, but it turns
out that anonymous_struct_prefix assumes that the entire string is
stored.  Also weird is that this code is demangling the linkage name
and then storing the demangled form back into the linkage name
attribute -- that seems bad, because what if some code wants to find
the actual linkage name?

Fixing these issues was non-trivial, though; and in the meantime this
patch seems like an improvement.  Regression tested on x86-64
Fedora 30.

gdb/ChangeLog
2020-03-16  Tom Tromey  <tromey@adacore.com>

	PR gdb/25663:
	* dwarf2/read.c (dwarf2_name): Strip leading namespaces after
	putting value into bcache.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6cb3cb5dccce71ef7b99602a31f55a9df45fe445..9211708d43240af841be42b69dc2af08bcc9bf1e 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-16  Tom Tromey  <tromey@adacore.com>
+
+       PR gdb/25663:
+       * dwarf2/read.c (dwarf2_name): Strip leading namespaces after
+       putting value into bcache.
+
 2020-03-16  Simon Marchi  <simon.marchi@efficios.com>
 
        PR gdb/21500

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 1706b96cc0443162675669cfba10d23428515174..88a60c1c73bb20543cd54e8ee9d2b7231c439688 100644 (file)
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -21799,19 +21799,17 @@ dwarf2_name (struct die_info *die, struct dwarf2_cu *cu)
              if (demangled == nullptr)
                return nullptr;
 
-             const char *base;
-
              DW_STRING (attr) = objfile->intern (demangled.get ());
              DW_STRING_IS_CANONICAL (attr) = 1;
-
-             /* Strip any leading namespaces/classes, keep only the base name.
-                DW_AT_name for named DIEs does not contain the prefixes.  */
-             base = strrchr (DW_STRING (attr), ':');
-             if (base && base > DW_STRING (attr) && base[-1] == ':')
-               return &base[1];
-             else
-               return DW_STRING (attr);
            }
+
+         /* Strip any leading namespaces/classes, keep only the base name.
+            DW_AT_name for named DIEs does not contain the prefixes.  */
+         const char *base = strrchr (DW_STRING (attr), ':');
+         if (base && base > DW_STRING (attr) && base[-1] == ':')
+           return &base[1];
+         else
+           return DW_STRING (attr);
        }
       break;