[ChangeLog]

2005-09-30  Graydon Hoare  <graydon@redhat.com>

	PR 1131.
	* tapsets.cxx (dwflpp::find_variable_and_frame_base)
	(dwflpp::translate_components)
	(dwflpp::resolve_unqualified_inner_typedie)
	(dwflpp::translate_final_fetch_or_store): New functions.
	(dwflpp::literal_stmt_for_local): Factor a bit.
	(variable_flavour_calculating_visitor::visit_target_symbol):
	Don't fault on lvalue, just collect an extra char.
	(var_expanding_copy_visitor::target_symbol_setter_functioncalls):
	New member.
	(var_expanding_copy_visitor::visit_assignment): New method.
	(var_expanding_copy_visitor::visit_target_symbol): Permit lvalues.

[runtime/ChangeLog]

2005-09-30  Graydon Hoare  <graydon@redhat.com>

	* loc2c-runtime.h (_put_user_asm): Fix bracket-matching.

4 files changed, 291 insertions, 132 deletions

diff --git a/ChangeLog b/ChangeLog
index a08ced87..5834b53d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2005-09-30  Graydon Hoare  <graydon@redhat.com>
+
+	PR 1131.
+	* tapsets.cxx (dwflpp::find_variable_and_frame_base)
+	(dwflpp::translate_components)
+	(dwflpp::resolve_unqualified_inner_typedie)
+	(dwflpp::translate_final_fetch_or_store): New functions.
+	(dwflpp::literal_stmt_for_local): Factor a bit.
+	(variable_flavour_calculating_visitor::visit_target_symbol): 
+	Don't fault on lvalue, just collect an extra char.
+	(var_expanding_copy_visitor::target_symbol_setter_functioncalls): 
+	New member.
+	(var_expanding_copy_visitor::visit_assignment): New method.
+	(var_expanding_copy_visitor::visit_target_symbol): Permit lvalues.
+
 2005-09-30  Frank Ch. Eigler  <fche@elastic.org>
 
 	* tapset/system_calls.stp (*_str): Simplified boolean test logic
diff --git a/runtime/ChangeLog b/runtime/ChangeLog
index ea2d22b0..548f908e 100644
--- a/runtime/ChangeLog
+++ b/runtime/ChangeLog
@@ -1,3 +1,7 @@
+2005-09-30  Graydon Hoare  <graydon@redhat.com>
+
+	* loc2c-runtime.h (_put_user_asm): Fix bracket-matching.
+
 2005-09-23  Martin Hunt  <hunt@redhat.com>
 
 	* map.c (_stp_map_sortn):  Call _stp_map_sort()
diff --git a/runtime/loc2c-runtime.h b/runtime/loc2c-runtime.h
index e25e0531..ed174db3 100644
--- a/runtime/loc2c-runtime.h
+++ b/runtime/loc2c-runtime.h
@@ -103,10 +103,10 @@
     int _bad = 0;							      \
     switch (size)							      \
       {									      \
-      case 1: __put_user_asm(((u8)(value),addr,_bad,"b","b","iq",1); break;   \
-      case 2: __put_user_asm(((u16)(value),addr,_bad,"w","w","ir",1); break;  \
-      case 4: __put_user_asm(((u32)(value),addr,_bad,"l","k","ir",1); break;  \
-      case 8: __put_user_asm(((u64)(value),addr,_bad,"q","","ir",1); break;   \
+      case 1: __put_user_asm(((u8)(value)),addr,_bad,"b","b","iq",1); break;  \
+      case 2: __put_user_asm(((u16)(value)),addr,_bad,"w","w","ir",1); break; \
+      case 4: __put_user_asm(((u32)(value)),addr,_bad,"l","k","ir",1); break; \
+      case 8: __put_user_asm(((u64)(value)),addr,_bad,"q","","ir",1); break;  \
       default: __put_user_bad();					      \
       }									      \
     if (_bad)								      \
@@ -137,10 +137,10 @@
     int _bad = 0;							      \
     switch (size)							      \
       {									      \
-      case 1: __put_user_asm(((u8)(value),addr,_bad,"stb",1); break;   	      \
-      case 2: __put_user_asm(((u16)(value),addr,_bad,"sth",1); break;  	      \
-      case 4: __put_user_asm(((u32)(value),addr,_bad,"stw",1); break;  	      \
-      case 8: __put_user_asm(((u64)(value),addr,_bad,"std",1); break; 	      \
+      case 1: __put_user_asm(((u8)(value)),addr,_bad,"stb",1); break;	      \
+      case 2: __put_user_asm(((u16)(value)),addr,_bad,"sth",1); break;	      \
+      case 4: __put_user_asm(((u32)(value)),addr,_bad,"stw",1); break;	      \
+      case 8: __put_user_asm(((u64)(value)),addr,_bad,"std",1); break;	      \
       default: __put_user_bad();					      \
       }									      \
     if (_bad)								      \
@@ -171,10 +171,10 @@
     int _bad = 0;							      \
     switch (size)							      \
       {									      \
-      case 1: __put_user_asm(((u8)(value),addr,_bad,"stb"); break;   	      \
-      case 2: __put_user_asm(((u16)(value),addr,_bad,"sth"); break;  	      \
-      case 4: __put_user_asm(((u32)(value),addr,_bad,"stw"); break;  	      \
-      case 8: __put_user_asm2(((u64)(value),addr,_bad); break;		      \
+      case 1: __put_user_asm(((u8)(value)),addr,_bad,"stb"); break;	      \
+      case 2: __put_user_asm(((u16)(value)),addr,_bad,"sth"); break;	      \
+      case 4: __put_user_asm(((u32)(value)),addr,_bad,"stw"); break;	      \
+      case 8: __put_user_asm2(((u64)(value)),addr,_bad); break;		      \
       default: __put_user_bad();					      \
       }									      \
     if (_bad)								      \
diff --git a/tapsets.cxx b/tapsets.cxx
index fae73e56..05839cfc 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -863,18 +863,18 @@ dwflpp
 					       NULL, NULL, NULL, NULL));
   }
 
-  string literal_stmt_for_local(Dwarf_Die *scope_die,
-				Dwarf_Addr pc,				
+  Dwarf_Attribute *
+  find_variable_and_frame_base (Dwarf_Die *scope_die,
+				Dwarf_Addr pc,		
 				string const & local,
-				vector<pair<target_symbol::component_type,
-				std::string> > const & components,
-				exp_type & ty)
+				Dwarf_Die *vardie,
+				Dwarf_Attribute *fb_attr_mem)
   {
-    assert (cu);
-
     Dwarf_Die *scopes;
-    Dwarf_Die vardie;
     int nscopes = 0;
+    Dwarf_Attribute *fb_attr = NULL;
+
+    assert (cu);
 
     if (scope_die)
       nscopes = dwarf_getscopes_die (scope_die, &scopes);
@@ -891,14 +891,13 @@ dwflpp
     int declaring_scope = dwarf_getscopevar (scopes, nscopes,
 					     local.c_str(),
 					     0, NULL, 0, 0,
-					     &vardie);
+					     vardie);
     if (declaring_scope < 0)
       {
 	throw semantic_error ("unable to find local '" + local + "'"
 			      + " near pc " + lex_cast_hex<string>(pc));
       }
 
-    Dwarf_Attribute fb_attr_mem, *fb_attr = NULL;
     for (int inner = 0; inner < nscopes; ++inner)
       {
 	switch (dwarf_tag (&scopes[inner]))
@@ -911,48 +910,29 @@ dwflpp
 	    if (inner >= declaring_scope)
 	      fb_attr = dwarf_attr_integrate (&scopes[inner],
 					      DW_AT_frame_base,
-					      &fb_attr_mem);
+					      fb_attr_mem);
 	    break;
 	  }
       }
+    return fb_attr;
+  }
 
-    if (sess.verbose)
-      clog << "finding location for local '" << local
-	   << "' near address " << hex << pc
-	   << ", module bias " << module_bias << dec
-	   << endl;
-
-    Dwarf_Attribute attr_mem;
-    if (dwarf_attr_integrate (&vardie, DW_AT_location, &attr_mem) == NULL)
-      {
-	throw semantic_error("failed to retrieve location "
-			     "attribute for local '" + local 
-			     + "' (dieoffset: " 
-			     + lex_cast_hex<string>(dwarf_dieoffset (&vardie)) 
-			     + ")");
-      }
-
-#define obstack_chunk_alloc malloc
-#define obstack_chunk_free free
-
-    struct obstack pool;
-    obstack_init (&pool);
-    struct location *tail = NULL;
-    struct location *head = c_translate_location (&pool, &loc2c_error, this,
-						  &loc2c_emit_address,
-						  1, module_bias,
-						  &attr_mem, pc,
-						  &tail, fb_attr);
 
-    if (dwarf_attr_integrate (&vardie, DW_AT_type, &attr_mem) == NULL)
-      throw semantic_error("failed to retrieve type "
-			   "attribute for local '" + local + "'");
-
-    Dwarf_Die die_mem, *die = &vardie;
+  Dwarf_Die *
+  translate_components(struct obstack *pool,
+		       struct location **tail,		       
+		       Dwarf_Addr pc,				
+		       vector<pair<target_symbol::component_type,
+		       std::string> > const & components,
+		       Dwarf_Die *vardie,
+		       Dwarf_Die *die_mem,
+		       Dwarf_Attribute *attr_mem)
+  {
+    Dwarf_Die *die = vardie;
     unsigned i = 0;
     while (i < components.size())
       {
-	die = dwarf_formref_die (&attr_mem, &die_mem);
+	die = dwarf_formref_die (attr_mem, die_mem);
 	const int typetag = dwarf_tag (die);
 	switch (typetag)
 	  {
@@ -966,14 +946,14 @@ dwflpp
 	    if (components[i].first == target_symbol::comp_literal_array_index)
 	      goto subscript;
 
-	    c_translate_pointer (&pool, 1, module_bias, die, &tail);
+	    c_translate_pointer (pool, 1, module_bias, die, tail);
 	    break;
 
 	  case DW_TAG_array_type:
 	    if (components[i].first == target_symbol::comp_literal_array_index)
 	      {
 	      subscript:
-		c_translate_array (&pool, 1, module_bias, die, &tail,
+		c_translate_array (pool, 1, module_bias, die, tail,
 				   NULL, lex_cast<Dwarf_Word>(components[i].second));
 		++i;
 	      }
@@ -985,7 +965,7 @@ dwflpp
 
 	  case DW_TAG_structure_type:
 	  case DW_TAG_union_type:
-	    switch (dwarf_child (die, &die_mem))
+	    switch (dwarf_child (die, die_mem))
 	      {
 	      case 1:		/* No children.  */
 		throw semantic_error ("empty struct "
@@ -1005,11 +985,11 @@ dwflpp
 	    while (dwarf_tag (die) != DW_TAG_member
 		   || ({ const char *member = dwarf_diename_integrate (die);
 		       member == NULL || string(member) != components[i].second; }))
-	      if (dwarf_siblingof (die, &die_mem) != 0)
+	      if (dwarf_siblingof (die, die_mem) != 0)
 		throw semantic_error ("field name " + components[i].second + " not found");
 
 	    if (dwarf_attr_integrate (die, DW_AT_data_member_location,
-				      &attr_mem) == NULL)
+				      attr_mem) == NULL)
 	      {
 		/* Union members don't usually have a location,
 		   but just use the containing union's location.  */
@@ -1019,9 +999,9 @@ dwflpp
 					+ " :" + string(dwarf_errmsg (-1)));
 	      }
 	    else
-	      c_translate_location (&pool, NULL, NULL, NULL, 1,
-				    module_bias, &attr_mem, pc,
-				    &tail, NULL);
+	      c_translate_location (pool, NULL, NULL, NULL, 1,
+				    module_bias, attr_mem, pc,
+				    tail, NULL);
 	    ++i;
 	    break;
 
@@ -1043,40 +1023,61 @@ dwflpp
 	  }
 
 	/* Now iterate on the type in DIE's attribute.  */
-	if (dwarf_attr_integrate (die, DW_AT_type, &attr_mem) == NULL)
+	if (dwarf_attr_integrate (die, DW_AT_type, attr_mem) == NULL)
 	  throw semantic_error ("cannot get type of field: " + string(dwarf_errmsg (-1)));
       }
+    return die;
+  }
 
-    /* Fetch the type DIE corresponding to the final location to be accessed.
-       It must be a base type or a typedef for one.  */
 
-    Dwarf_Die typedie_mem;
+  Dwarf_Die *
+  resolve_unqualified_inner_typedie (Dwarf_Die *typedie_mem,
+				     Dwarf_Attribute *attr_mem)
+  {
+    ;
     Dwarf_Die *typedie;
-    int typetag;
+    int typetag = 0;
     while (1)
-      {
-	typedie = dwarf_formref_die (&attr_mem, &typedie_mem);
+      {	      
+	typedie = dwarf_formref_die (attr_mem, typedie_mem);
 	if (typedie == NULL)
-	  throw semantic_error ("cannot get type of field: " + string(dwarf_errmsg (-1)));
+	  throw semantic_error ("cannot get type: " + string(dwarf_errmsg (-1)));
 	typetag = dwarf_tag (typedie);
 	if (typetag != DW_TAG_typedef && 
 	    typetag != DW_TAG_const_type &&
 	    typetag != DW_TAG_volatile_type)
 	  break;
-	if (dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem) == NULL)
-	  throw semantic_error ("cannot get type of field: " + string(dwarf_errmsg (-1)));
+	if (dwarf_attr_integrate (typedie, DW_AT_type, attr_mem) == NULL)
+	  throw semantic_error ("cannot get type of pointee: " + string(dwarf_errmsg (-1)));
       }
+    return typedie;
+  }
 
 
-    // If we have a base type, we will fetch it into pe_long.
-    //
-    // If we have a pointer to non-char, we will cast it to uintptr_t, and fetch
-    // into pe_long.
-    //
-    // If we have a pointer to char, we will fetch into pe_string, using 
-    // deref_string() over in loc2c-runtime.h
+  void 
+  translate_final_fetch_or_store (struct obstack *pool,
+				  struct location **tail,
+				  Dwarf_Addr module_bias,
+				  Dwarf_Die *die,
+				  Dwarf_Attribute *attr_mem,
+				  bool lvalue,
+				  string & prelude,
+				  string & postlude,
+				  exp_type & ty)
+  {
+    /* First boil away any qualifiers associated with the type DIE of
+       the final location to be accessed.  */
 
-    string prelude, postlude;
+    Dwarf_Die typedie_mem;
+    Dwarf_Die *typedie;
+    int typetag;
+
+    typedie = resolve_unqualified_inner_typedie (&typedie_mem, attr_mem);
+    typetag = dwarf_tag (typedie);
+
+    /* Then switch behavior depending on the type of fetch/store we
+       want, and the type and pointer-ness of the final location. */
+    
     switch (typetag)
       {
       default:
@@ -1087,43 +1088,35 @@ dwflpp
       case DW_TAG_enumeration_type:
       case DW_TAG_base_type:
 	ty = pe_long;
-	c_translate_fetch (&pool, 1, module_bias, die, typedie, &tail,
-			   "THIS->__retvalue");
+	if (lvalue)
+	  c_translate_store (pool, 1, module_bias, die, typedie, tail,
+			     "THIS->value");
+	else	  
+	  c_translate_fetch (pool, 1, module_bias, die, typedie, tail,
+			     "THIS->__retvalue");
 	break;
 
       case DW_TAG_array_type:
       case DW_TAG_pointer_type:
+
+	if (lvalue)
+	  throw semantic_error ("cannot store into target pointer value");
+
 	{
 	  Dwarf_Die pointee_typedie_mem;
 	  Dwarf_Die *pointee_typedie;
 	  Dwarf_Word pointee_encoding;
 	  Dwarf_Word pointee_byte_size = 0;
-	  int pointee_typetag;
 
-	  if (dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem) == NULL)
+	  if (dwarf_attr_integrate (typedie, DW_AT_type, attr_mem) == NULL)
 	    throw semantic_error ("cannot get type of pointer: " + string(dwarf_errmsg (-1)));
-	  
-	  while (1)
-	    {	      
-	      pointee_typedie = dwarf_formref_die (&attr_mem, &pointee_typedie_mem);
-
-	      if (pointee_typedie == NULL)
-		throw semantic_error ("cannot get type of pointee: " + string(dwarf_errmsg (-1)));
-	      
-	      pointee_typetag = dwarf_tag (pointee_typedie);
-
-	      if (pointee_typetag != DW_TAG_typedef && 
-		  pointee_typetag != DW_TAG_const_type &&
-		  pointee_typetag != DW_TAG_volatile_type)
-		break;
-	      if (dwarf_attr_integrate (pointee_typedie, DW_AT_type, &attr_mem) == NULL)
-		throw semantic_error ("cannot get type of pointee: " + string(dwarf_errmsg (-1)));
-	    }
 
-	  if (dwarf_attr_integrate (pointee_typedie, DW_AT_byte_size, &attr_mem))
-	    dwarf_formudata (&attr_mem, &pointee_byte_size);
+	  pointee_typedie = resolve_unqualified_inner_typedie (&pointee_typedie_mem, attr_mem);
+
+	  if (dwarf_attr_integrate (pointee_typedie, DW_AT_byte_size, attr_mem))
+	    dwarf_formudata (attr_mem, &pointee_byte_size);
 	  
-	  dwarf_formudata (dwarf_attr_integrate (pointee_typedie, DW_AT_encoding, &attr_mem), 
+	  dwarf_formudata (dwarf_attr_integrate (pointee_typedie, DW_AT_encoding, attr_mem), 
 			   &pointee_encoding);
 
 	  // We have the pointer: cast it to an integral type via &(*(...))
@@ -1135,14 +1128,86 @@ dwflpp
 
 	  ty = pe_long;
 	  if (typetag == DW_TAG_array_type)
-	    c_translate_array (&pool, 1, module_bias, typedie, &tail, NULL, 0);
+	    c_translate_array (pool, 1, module_bias, typedie, tail, NULL, 0);
 	  else
-	    c_translate_pointer (&pool, 1, module_bias, typedie, &tail);
-	  c_translate_addressof (&pool, 1, module_bias, NULL, pointee_typedie, &tail, 
+	    c_translate_pointer (pool, 1, module_bias, typedie, tail);
+	  c_translate_addressof (pool, 1, module_bias, NULL, pointee_typedie, tail, 
 				 "THIS->__retvalue");
 	}
 	break;	
       }
+  }  
+
+
+  string 
+  literal_stmt_for_local (Dwarf_Die *scope_die,
+			  Dwarf_Addr pc,				
+			  string const & local,
+			  vector<pair<target_symbol::component_type,
+			  std::string> > const & components,
+			  bool lvalue,
+			  exp_type & ty)
+  {
+    Dwarf_Die vardie;
+    Dwarf_Attribute fb_attr_mem, *fb_attr = NULL;
+
+    fb_attr = find_variable_and_frame_base (scope_die, pc, local, 
+					    &vardie, &fb_attr_mem);
+
+    if (sess.verbose)
+      clog << "finding location for local '" << local
+	   << "' near address " << hex << pc
+	   << ", module bias " << module_bias << dec
+	   << endl;
+
+    Dwarf_Attribute attr_mem;
+    if (dwarf_attr_integrate (&vardie, DW_AT_location, &attr_mem) == NULL)
+      {
+	throw semantic_error("failed to retrieve location "
+			     "attribute for local '" + local 
+			     + "' (dieoffset: " 
+			     + lex_cast_hex<string>(dwarf_dieoffset (&vardie)) 
+			     + ")");
+      }
+
+#define obstack_chunk_alloc malloc
+#define obstack_chunk_free free
+
+    struct obstack pool;
+    obstack_init (&pool);
+    struct location *tail = NULL;
+
+    /* Given $foo->bar->baz[NN], translate the location of foo. */
+
+    struct location *head = c_translate_location (&pool, &loc2c_error, this,
+						  &loc2c_emit_address,
+						  1, module_bias,
+						  &attr_mem, pc,
+						  &tail, fb_attr);
+
+    if (dwarf_attr_integrate (&vardie, DW_AT_type, &attr_mem) == NULL)
+      throw semantic_error("failed to retrieve type "
+			   "attribute for local '" + local + "'");
+
+
+    /* Translate the ->bar->baz[NN] parts. */
+
+    Dwarf_Die die_mem, *die = NULL;
+    die = translate_components (&pool, &tail, pc, components, 
+				&vardie, &die_mem, &attr_mem);
+
+    /* Translate the assignment part, either 
+       x = $foo->bar->baz[NN] 
+       or 
+       $foo->bar->baz[NN] = x
+    */
+
+    string prelude, postlude;
+    translate_final_fetch_or_store (&pool, &tail, module_bias, 
+				    die, &attr_mem, lvalue,
+				    prelude, postlude, ty);
+
+    /* Write the translation to a string. */
     
     size_t bufsz = 1024;
     char *buf = static_cast<char*>(malloc(bufsz));
@@ -1500,20 +1565,16 @@ target_variable_flavour_calculating_visitor::visit_target_symbol (target_symbol
 {
   assert(e->base_name.size() > 0 && e->base_name[0] == '$');
 
-  if (is_active_lvalue(e))
-    {
-      q.sess.print_error (semantic_error("read-only special variable "
-                                         + e->base_name + " used as lvalue",
-                                         e->tok));
-    }
-
   try
     {      
+      bool lvalue = is_active_lvalue(e);
+      flavour += lvalue ? 'w' : 'r';
       exp_type ty;
       string expr = q.dw.literal_stmt_for_local(scope_die, 
 						addr,
 						e->base_name.substr(1),
 						e->components,
+						lvalue,
 						ty);      
       switch (ty)
 	{
@@ -2043,6 +2104,7 @@ var_expanding_copy_visitor
   : public deep_copy_visitor
 {
   static unsigned tick;
+  stack<functioncall**> target_symbol_setter_functioncalls;
 
   dwarf_query & q;
   Dwarf_Die *scope_die;
@@ -2051,38 +2113,89 @@ var_expanding_copy_visitor
   var_expanding_copy_visitor(dwarf_query & q, Dwarf_Die *sd, Dwarf_Addr a)
     : q(q), scope_die(sd), addr(a)
   {}
+  void visit_assignment (assignment* e);
   void visit_target_symbol (target_symbol* e);
 };
 
 
 unsigned var_expanding_copy_visitor::tick = 0;
 
-
 void
-var_expanding_copy_visitor::visit_target_symbol (target_symbol *e)
+var_expanding_copy_visitor::visit_assignment (assignment* e)
 {
-  assert(e->base_name.size() > 0 && e->base_name[0] == '$');
+  // Our job would normally be to require() the left and right sides
+  // into a new assignment. What we're doing is slightly trickier:
+  // we're pushing a functioncall** onto a stack, and if our left
+  // child sets the functioncall* for that value, we're going to
+  // assume our left child was a target symbol -- transformed into a
+  // set_target_foo(value) call, and it wants to take our right child
+  // as the argument "value".
+  //
+  // This is why some people claim that languages with
+  // constructor-decomposing case expressions have a leg up on
+  // visitors.
+
+  functioncall *fcall = NULL;
+  expression *new_left, *new_right;
 
-  if (is_active_lvalue(e))
+  target_symbol_setter_functioncalls.push (&fcall);
+  require<expression*> (this, &new_left, e->left);
+  target_symbol_setter_functioncalls.pop ();
+  require<expression*> (this, &new_right, e->right);
+
+  if (fcall != NULL)
     {
-      // No need to be verbose: the flavour-gathering visitor
-      // already printed a message for this exact case.
-      throw semantic_error ("due to failed target variable resolution");
+      // Our left child is informing us that it was a target variable
+      // and it has been replaced with a set_target_foo() function
+      // call; we are going to provide that function call -- with the
+      // right child spliced in as sole argument -- in place of
+      // ourselves, in the deep copy we're in the middle of making.
+
+      // FIXME: for the time being, we only support plan $foo = bar,
+      // not += or any other op= variant. This is fixable, but a bit
+      // ugly.
+      if (e->op != "=")
+	throw semantic_error ("Operator-assign expressions on target "
+			     "variables not implemented", e->tok);
+
+      assert (new_left == fcall);
+      fcall->args.push_back (new_right);
+      provide <expression*> (this, fcall);
     }
+  else
+    {
+      assignment* n = new assignment;
+      n->op = e->op;
+      n->tok = e->tok;
+      n->left = new_left;
+      n->right = new_right;
+      provide <assignment*> (this, n);
+    }
+}
 
-  string fname = "get_" + e->base_name.substr(1) + "_" + lex_cast<string>(tick++);
 
-  // synthesize a function
+void
+var_expanding_copy_visitor::visit_target_symbol (target_symbol *e)
+{
+  assert(e->base_name.size() > 0 && e->base_name[0] == '$');
+
+  // Synthesize a function.
   functiondecl *fdecl = new functiondecl;
   embeddedcode *ec = new embeddedcode;
   ec->tok = e->tok;
+  bool lvalue = is_active_lvalue(e);
+  string fname = (string(lvalue ? "set" : "get") 
+		  + "_" + e->base_name.substr(1) 
+		  + "_" + lex_cast<string>(tick++));
+
   try
-    {      
-      ec->code = q.dw.literal_stmt_for_local(scope_die, 
-					     addr,
-					     e->base_name.substr(1),
-					     e->components,
-					     fdecl->type);
+    {
+      ec->code = q.dw.literal_stmt_for_local (scope_die, 
+					      addr,
+					      e->base_name.substr(1),
+					      e->components,
+					      lvalue,
+					      fdecl->type);
     }
   catch (const semantic_error& er)
     {
@@ -2090,15 +2203,42 @@ var_expanding_copy_visitor::visit_target_symbol (target_symbol *e)
       // already printed a message for this exact case.
       throw semantic_error ("due to failed target variable resolution");
     }
+
   fdecl->name = fname;
   fdecl->body = ec;
+  if (lvalue)
+    {
+      // Modify the fdecl so it carries a single pe_long formal
+      // argument called "value".
+
+      // FIXME: For the time being we only support setting target
+      // variables which have base types; these are 'pe_long' in
+      // stap's type vocabulary.  Strings and pointers might be
+      // reasonable, some day, but not today.
+
+      vardecl *v = new vardecl;
+      v->type = pe_long;
+      v->name = "value";
+      v->tok = e->tok;
+      fdecl->formal_args.push_back(v);
+    }
   q.sess.functions.push_back(fdecl);
 
-  // synthesize a call
+  // Synthesize a functioncall.
   functioncall* n = new functioncall;
   n->tok = e->tok;
   n->function = fname;
   n->referent = NULL;
+
+  if (lvalue)
+    {
+      // Provide the functioncall to our parent, so that it can be
+      // used to substitute for the assignment node immediately above
+      // us.
+      assert(!target_symbol_setter_functioncalls.empty());
+      *(target_symbol_setter_functioncalls.top()) = n;
+    }
+
   provide <functioncall*> (this, n);
 }