[PATCH] D94431: Avoid fragile type lookups in GDB pretty printer

[Moritz Sichert via Phabricator via llvm-commits]

MoritzS created this revision.
MoritzS added reviewers: csigg, dblaikie.
MoritzS requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Instead of using the type llvm::StringMapEntry<{stringified_value_type}>
use only the base class llvm::StringMapEntryBase and calculate the
offsets of the member variables manually. The approach with stringifying
the name of the value type is pretty fragile as it can easily break with
local and dependent types.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94431

Files:
  llvm/utils/gdb-scripts/prettyprinters.py


Index: llvm/utils/gdb-scripts/prettyprinters.py
===================================================================
--- llvm/utils/gdb-scripts/prettyprinters.py
+++ llvm/utils/gdb-scripts/prettyprinters.py
@@ -211,7 +211,7 @@
     it = self.val['TheTable']
     end = (it + self.val['NumBuckets'])
     value_ty = self.val.type.template_argument(0)
-    entry_ty = gdb.lookup_type('llvm::StringMapEntry<{}>'.format(value_ty.name))
+    entry_base_ty = gdb.lookup_type('llvm::StringMapEntryBase')
     tombstone = gdb.parse_and_eval('llvm::StringMapImpl::TombstoneIntVal');
 
     while it != end:
@@ -220,15 +220,17 @@
         it = it + 1
         continue
 
-      entry_ptr = it_deref.cast(entry_ty.pointer())
+      entry_ptr = it_deref.cast(entry_base_ty.pointer())
       entry = entry_ptr.dereference()
 
       str_len = entry['keyLength']
-      str_data = (entry_ptr + 1).cast(gdb.lookup_type('char').const().pointer())
+      value_ptr = (entry_ptr + 1).cast(value_ty.pointer())
+      str_data = (entry_ptr + 1).cast(gdb.lookup_type('uintptr_t')) + max(value_ty.sizeof, entry_base_ty.alignof)
+      str_data = str_data.cast(gdb.lookup_type('char').const().pointer())
       string_ref = gdb.Value(struct.pack('PN', int(str_data), int(str_len)), gdb.lookup_type('llvm::StringRef'))
       yield 'key', string_ref
 
-      value = entry['second']
+      value = value_ptr.dereference()
       yield 'value', value
 
       it = it + 1


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