[PATCH 4/6] Full paths in DAP stackTrace responses

[Tom Tromey <tromey@adacore.com>]

Vladimir Makaev noticed that, in some cases, a DAP stackTrace response
would include a relative path name for the "path" component.

This patch changes the frame decorator code to add a new DAP-specific
decorator, and changes the DAP entry point to frame filters to use it.
This decorator prefers the symtab's full name, and does not fall back
to the solib's name.

I'm not entirely happy with this patch, because if a user frame filter
uses FrameDecorator, it may still do the wrong thing.  It would be
better to have frame filters return symtab-like objects instead, or to
have a separate method to return the full path to the source file.

I also tend to think that the solib fallback behavior of
FrameDecorator is a mistake.  If this is ever needed, it seems to me
that it should be a separate method.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30665
---
 gdb/python/lib/gdb/FrameDecorator.py | 111 +++++++++++++++++++++--------------
 gdb/python/lib/gdb/frames.py         |  14 ++++-
 2 files changed, 78 insertions(+), 47 deletions(-)

diff --git a/gdb/python/lib/gdb/FrameDecorator.py b/gdb/python/lib/gdb/FrameDecorator.py
index c4a7806e434..22d5fa4d0a9 100644
--- a/gdb/python/lib/gdb/FrameDecorator.py
+++ b/gdb/python/lib/gdb/FrameDecorator.py
@@ -16,34 +16,8 @@
 import gdb
 
 
-class FrameDecorator(object):
-    """Basic implementation of a Frame Decorator"""
-
-    """ This base frame decorator decorates a frame or another frame
-    decorator, and provides convenience methods.  If this object is
-    wrapping a frame decorator, defer to that wrapped object's method
-    if it has one.  This allows for frame decorators that have
-    sub-classed FrameDecorator object, but also wrap other frame
-    decorators on the same frame to correctly execute.
-
-    E.g
-
-    If the result of frame filters running means we have one gdb.Frame
-    wrapped by multiple frame decorators, all sub-classed from
-    FrameDecorator, the resulting hierarchy will be:
-
-    Decorator1
-      -- (wraps) Decorator2
-        -- (wraps) FrameDecorator
-          -- (wraps) gdb.Frame
-
-    In this case we have two frame decorators, both of which are
-    sub-classed from FrameDecorator.  If Decorator1 just overrides the
-    'function' method, then all of the other methods are carried out
-    by the super-class FrameDecorator.  But Decorator2 may have
-    overriden other methods, so FrameDecorator will look at the
-    'base' parameter and defer to that class's methods.  And so on,
-    down the chain."""
+class _FrameDecoratorBase(object):
+    """Base class of frame decorators."""
 
     # 'base' can refer to a gdb.Frame or another frame decorator.  In
     # the latter case, the child class will have called the super
@@ -122,22 +96,6 @@ class FrameDecorator(object):
         frame = self.inferior_frame()
         return frame.pc()
 
-    def filename(self):
-        """Return the filename associated with this frame, detecting
-        and returning the appropriate library name is this is a shared
-        library."""
-
-        if hasattr(self._base, "filename"):
-            return self._base.filename()
-
-        frame = self.inferior_frame()
-        sal = frame.find_sal()
-        if not sal.symtab or not sal.symtab.filename:
-            pc = frame.pc()
-            return gdb.solib_name(pc)
-        else:
-            return sal.symtab.filename
-
     def frame_args(self):
         """Return an iterable of frame arguments for this frame, if
         any.  The iterable object contains objects conforming with the
@@ -198,6 +156,71 @@ class FrameDecorator(object):
         return self._base
 
 
+class FrameDecorator(_FrameDecoratorBase):
+    """Basic implementation of a Frame Decorator"""
+
+    """ This base frame decorator decorates a frame or another frame
+    decorator, and provides convenience methods.  If this object is
+    wrapping a frame decorator, defer to that wrapped object's method
+    if it has one.  This allows for frame decorators that have
+    sub-classed FrameDecorator object, but also wrap other frame
+    decorators on the same frame to correctly execute.
+
+    E.g
+
+    If the result of frame filters running means we have one gdb.Frame
+    wrapped by multiple frame decorators, all sub-classed from
+    FrameDecorator, the resulting hierarchy will be:
+
+    Decorator1
+      -- (wraps) Decorator2
+        -- (wraps) FrameDecorator
+          -- (wraps) gdb.Frame
+
+    In this case we have two frame decorators, both of which are
+    sub-classed from FrameDecorator.  If Decorator1 just overrides the
+    'function' method, then all of the other methods are carried out
+    by the super-class FrameDecorator.  But Decorator2 may have
+    overriden other methods, so FrameDecorator will look at the
+    'base' parameter and defer to that class's methods.  And so on,
+    down the chain."""
+
+    def filename(self):
+        """Return the filename associated with this frame, detecting
+        and returning the appropriate library name is this is a shared
+        library."""
+
+        if hasattr(self._base, "filename"):
+            return self._base.filename()
+
+        frame = self.inferior_frame()
+        sal = frame.find_sal()
+        if not sal.symtab or not sal.symtab.filename:
+            pc = frame.pc()
+            return gdb.solib_name(pc)
+        else:
+            return sal.symtab.filename
+
+
+class DAPFrameDecorator(_FrameDecoratorBase):
+    """Like FrameDecorator, but has slightly different results
+    for the "filename" method."""
+
+    def filename(self):
+        """Return the filename associated with this frame, detecting
+        and returning the appropriate library name is this is a shared
+        library."""
+
+        if hasattr(self._base, "filename"):
+            return self._base.filename()
+
+        frame = self.inferior_frame()
+        sal = frame.find_sal()
+        if sal.symtab is not None:
+            return sal.symtab.fullname()
+        return None
+
+
 class SymValueWrapper(object):
     """A container class conforming to the Symbol/Value interface
     which holds frame locals or frame arguments."""
diff --git a/gdb/python/lib/gdb/frames.py b/gdb/python/lib/gdb/frames.py
index cff3ba07704..104ff4bb203 100644
--- a/gdb/python/lib/gdb/frames.py
+++ b/gdb/python/lib/gdb/frames.py
@@ -18,7 +18,7 @@
 
 import gdb
 from gdb.FrameIterator import FrameIterator
-from gdb.FrameDecorator import FrameDecorator
+from gdb.FrameDecorator import FrameDecorator, DAPFrameDecorator
 import itertools
 import collections
 
@@ -172,7 +172,11 @@ def _frame_iterator(frame, frame_low, frame_high, always):
 
     # Apply a basic frame decorator to all gdb.Frames.  This unifies
     # the interface.
-    frame_iterator = map(FrameDecorator, frame_iterator)
+    if always:
+        decorator = DAPFrameDecorator
+    else:
+        decorator = FrameDecorator
+    frame_iterator = map(decorator, frame_iterator)
 
     for ff in sorted_list:
         frame_iterator = ff.filter(frame_iterator)
@@ -214,7 +218,11 @@ def frame_iterator(frame, frame_low, frame_high):
     """Helper function that will execute the chain of frame filters.
     Each filter is executed in priority order.  After the execution
     completes, slice the iterator to frame_low - frame_high range.  An
-    iterator is always returned.
+    iterator is always returned.  The iterator will always yield
+    frame decorator objects, but note that these decorators have
+    slightly different semantics from the ordinary ones: they will
+    always return a fully-qualified 'filename' (if possible) and will
+    never substitute the objfile name.
 
     Arguments:
         frame: The initial frame.

-- 
2.40.1