[RFA] Updated path expression computations for varobj trees

Keith Seitz
2011-12-16T22:56:19Z

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Hi,

Revisions on my 10586 patch has exposed a couple of shortcomings with my
recent varobj tree testing infrastructure's handling of path expressions.

I am proposing the attached patch which updates comments and fixes a
bunch of path expression problems. The most notable change for this is
an assumption that all varobjs are compound types unless the type is
recognized as a simple type.

With this patch, I can now test path expressions in my 10586 patch which
I had previously omitted.

Comments/questions/concerns?

Keith

testsuite/ChangeLog
2011-12-16 Keith Seitz <keiths@redhat.com>

* lib/mi-support.exp: Expand comments about PATH_EXPR.
(varobj_tree::get_path_expr): Assume that all varobjs are
compound unless they are known simple types.
Adjust path expressions based on parent type, path parent type,
and tree language.
(varobj_tree::walk_tree): Add LANGUAGE parameter and save it into
the root varobj.
(mi_walk_varobj_tree): Add LANGUAGE parameter.

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diff --git a/gdb/testsuite/lib/mi-support.exp b/gdb/testsuite/lib/mi-support.exp
index e1845f6..1f2b79c 100644
--- a/gdb/testsuite/lib/mi-support.exp
+++ b/gdb/testsuite/lib/mi-support.exp
@@ -2012,7 +2012,7 @@ proc mi_get_features {} {
# }
# }
#
-# mi_walk_varobj_tree $tree
+# mi_walk_varobj_tree c++ $tree
#
# If you'd prefer to walk the tree using your own callback,
# simply pass the name of the callback to mi_walk_varobj_tree.
@@ -2038,6 +2038,9 @@ proc mi_get_features {} {
# type - the type of this variable (type="type" in the output
# of -var-list-children, or the special tag "anonymous"
# path_expr - the "-var-info-path-expression" for this variable
+# NOTE: This member cannot be used reliably with typedefs.
+# Use with caution!
+# See notes inside get_path_expr for more.
# parent - the variable name of the parent varobj
# children - a list of children variable names (which are the
# names Tcl arrays, not object names)
@@ -2084,7 +2087,8 @@ namespace eval ::varobj_tree {
}

# The default callback used by mi_walk_varobj_tree. This callback
- # simply checks all of VAR's children.
+ # simply checks all of VAR's children. It specifically does not test
+ # path expressions, since that is very problematic.
#
# This procedure may be used in custom callbacks.
proc test_children_callback {variable_name} {
@@ -2154,20 +2158,82 @@ namespace eval ::varobj_tree {
# parent varobj whose variable name is given by PARENT_VARIABLE.
proc get_path_expr {parent_variable name type} {
upvar #0 $parent_variable parent
+ upvar #0 $parent_variable path_parent

# If TYPE is "", this is one of the CPLUS_FAKE_CHILD varobjs,
- # which has no path expression
- if {[string length $type] == 0} {
+ # which has no path expression. Likewsise for anonymous structs
+ # and unions.
+ if {[string length $type] == 0 \
+ || [string compare $type "anonymous"] == 0} {
return ""
}

# Find the path parent variable.
while {![is_path_expr_parent $parent_variable]} {
- set parent_variable $parent(parent)
- upvar #0 $parent_variable parent
- }
+ set parent_variable $path_parent(parent)
+ upvar #0 $parent_variable path_parent
+ }
+
+ # This is where things get difficult. We do not actually know
+ # the real type for variables defined via typedefs, so we don't actually
+ # know whether the parent is a structure/union or not.
+ #
+ # So we assume everything that isn't a simple type is a compound type.
+ set stars ""
+ regexp {\*+} $parent(type) stars
+ set is_compound 1
+ set delim {[\ \*&]+}
+ switch -regexp $parent(type) \
+ bool$delim - \
+ char$delim - \
+ char16_t$delim - \
+ char32_t$delim - \
+ double$delim - \
+ float$delim - \
+ int$delim - \
+ long$delim - \
+ short$delim - \
+ signed$delim - \
+ unsigned$delim - \
+ void$delim - \
+ wchar_t$delim {
+ set is_compound 0
+ } \
+ \
+ default {
+ # We assume everything is a compound type except pointers
+ # to structures, which are automatically dereferenced by
+ # varobj. All other pointers are simple types.
+ if {[string length $stars] > 1} {
+ set is_compound 0
+ }
+ }
+
+ if {[string index $parent(type) end] == "\]"} {
+ # Parent is an array.
+ return "($path_parent(path_expr))\[$name\]"
+ } elseif {$is_compound} {
+ # Parent is a structure or union or a pointer to one.
+ if {[string length $stars]} {
+ set join "->"
+ } else {
+ set join "."
+ }

- return "(($parent(path_expr)).$name)"
+ global root
+
+ # To make matters even more hideous, varobj.c has slightly different
+ # path expressions for C and C++.
+ set path_expr "($path_parent(path_expr))$join$name"
+ if {[string compare -nocase $root(language) "c"] == 0} {
+ return $path_expr
+ } else {
+ return "($path_expr)"
+ }
+ } else {
+ # Parent is a pointer.
+ return "*($path_parent(path_expr))"
+ }
}

# Process the CHILDREN (a list of varobj_tree elements) of the variable
@@ -2208,7 +2274,7 @@ namespace eval ::varobj_tree {

# The main procedure to call the given CALLBACK on the elements of the
# given varobj TREE. See detailed explanation above.
- proc walk_tree {tree callback} {
+ proc walk_tree {language tree callback} {
global root

if {[llength $tree] < 3} {
@@ -2216,6 +2282,7 @@ namespace eval ::varobj_tree {
}

# Create root node and process the tree.
+ array set root [list language $language]
array set root [list obj_name "root"]
array set root [list display_name "root"]
array set root [list type "root"]
@@ -2259,7 +2326,8 @@ proc mi_varobj_tree_test_children_callback {variable} {

# Walk the variable object tree given by TREE, calling the specified
# CALLBACK. By default this uses mi_varobj_tree_test_children_callback.
-proc mi_walk_varobj_tree {tree {callback \
- mi_varobj_tree_test_children_callback}} {
- ::varobj_tree::walk_tree $tree $callback
+proc mi_walk_varobj_tree {language tree \
+ {callback \
+ mi_varobj_tree_test_children_callback}} {
+ ::varobj_tree::walk_tree $language $tree $callback
}