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[v3,1/3] gdb: Do not create variables when parsing expressions

Message ID 20240901214351.3134941-2-nt8r@protonmail.com
State New
Headers
Series Tab complete convenience variables |

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Commit Message

Antonio Rische Sept. 1, 2024, 9:44 p.m. UTC 
  We do this by introducing a new type of expression for internalvars
that had not been given a value at parse time.

This is not particularly useful on its own, but allows us to parse
expressions without having side-effects on the set of internalvars.

This will then allow us to tab-complete internalvars in expressions
without creating new internalvars, which would otherwise defeat the
purpose of tab completion (completing only variables that have been
set).
---
 gdb/ada-exp.h       | 12 +++++++--
 gdb/ax-gdb.c        | 61 +++++++++++++++++++++++++++++++++++++--------
 gdb/cli/cli-utils.c |  2 +-
 gdb/expop.h         | 55 +++++++++++++++++++++++++++++++++++++++-
 gdb/parse.c         |  7 +++---
 5 files changed, 119 insertions(+), 18 deletions(-)
diff mbox series

Patch

diff --git a/gdb/ada-exp.h b/gdb/ada-exp.h
index 94e4ea0f4..d7efcb105 100644
--- a/gdb/ada-exp.h
+++ b/gdb/ada-exp.h
@@ -534,8 +534,16 @@  class ada_assign_operation
      assignment.  */
   value *eval_for_resolution (struct expression *exp)
   {
-    return std::get<0> (m_storage)->evaluate (nullptr, exp,
-					      EVAL_AVOID_SIDE_EFFECTS);
+    operation *lhs_op = std::get<0> (m_storage).get ();
+
+    /* If the operation is an internalvar that was not initialized at
+     parse time, ensure that it exists. */
+    auto *uninit_var_op = dynamic_cast<uninit_internalvar_operation *>
+			  (lhs_op);
+    if (uninit_var_op != nullptr)
+      lookup_internalvar (uninit_var_op->get_name ());
+
+    return lhs_op->evaluate (nullptr, exp, EVAL_AVOID_SIDE_EFFECTS);
   }
 
   /* The parser must construct the assignment node before parsing the
diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index 3d619012b..46b618537 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -1668,6 +1668,33 @@  register_operation::do_generate_ax (struct expression *exp,
   value->type = register_type (ax->gdbarch, reg);
 }
 
+/* Generate remote agent bytecode for the operation that accesses a
+   yet-to-be-initialized internalvar.  */
+void
+uninit_internalvar_operation::do_generate_ax (struct expression *exp,
+				       struct agent_expr *ax,
+				       struct axs_value *value,
+				       struct type *cast_type)
+{
+  const char *name = get_name ();
+  struct internalvar *var = lookup_only_internalvar (name);
+  struct trace_state_variable *tsv;
+
+  tsv = find_trace_state_variable (name);
+  if (tsv != nullptr)
+    {
+      ax_tsv (ax, aop_getv, tsv->number);
+      if (ax->tracing)
+	ax_tsv (ax, aop_tracev, tsv->number);
+      /* Trace state variables are always 64-bit integers.  */
+      value->kind = axs_rvalue;
+      value->type = builtin_type (ax->gdbarch)->builtin_long_long;
+    }
+  else if (!compile_internalvar_to_ax (var, ax, value))
+    error (_("$%s is not a trace state variable; GDB agent "
+	     "expressions cannot use convenience variables."), name);
+}
+
 void
 internalvar_operation::do_generate_ax (struct expression *exp,
 				       struct agent_expr *ax,
@@ -1679,7 +1706,7 @@  internalvar_operation::do_generate_ax (struct expression *exp,
   struct trace_state_variable *tsv;
 
   tsv = find_trace_state_variable (name);
-  if (tsv)
+  if (tsv != nullptr)
     {
       ax_tsv (ax, aop_getv, tsv->number);
       if (ax->tracing)
@@ -1688,7 +1715,7 @@  internalvar_operation::do_generate_ax (struct expression *exp,
       value->kind = axs_rvalue;
       value->type = builtin_type (ax->gdbarch)->builtin_long_long;
     }
-  else if (! compile_internalvar_to_ax (var, ax, value))
+  else if (!compile_internalvar_to_ax (var, ax, value))
     error (_("$%s is not a trace state variable; GDB agent "
 	     "expressions cannot use convenience variables."), name);
 }
@@ -1911,6 +1938,26 @@  op_this_operation::do_generate_ax (struct expression *exp,
 	   sym->print_name ());
 }
 
+/* Get the name of the internalvar referenced by an operation, or
+   nullptr if the operation does not reference an internalvar.  */
+static const char *
+internalvar_op_name (operation *op)
+{
+  gdb_assert (op->opcode () == OP_INTERNALVAR);
+
+  internalvar_operation *ivar_op
+    = dynamic_cast<internalvar_operation *> (op);
+  if (ivar_op != nullptr)
+    return internalvar_name (ivar_op->get_internalvar ());
+
+  uninit_internalvar_operation *uninit_ivar_op
+    = dynamic_cast<uninit_internalvar_operation *> (op);
+  if (uninit_ivar_op != nullptr)
+    return uninit_ivar_op->get_name ();
+
+  return nullptr;
+}
+
 void
 assign_operation::do_generate_ax (struct expression *exp,
 				  struct agent_expr *ax,
@@ -1921,10 +1968,7 @@  assign_operation::do_generate_ax (struct expression *exp,
   if (subop->opcode () != OP_INTERNALVAR)
     error (_("May only assign to trace state variables"));
 
-  internalvar_operation *ivarop
-    = gdb::checked_static_cast<internalvar_operation *> (subop);
-
-  const char *name = internalvar_name (ivarop->get_internalvar ());
+  const char *name = internalvar_op_name (subop);
   struct trace_state_variable *tsv;
 
   std::get<1> (m_storage)->generate_ax (exp, ax, value);
@@ -1950,10 +1994,7 @@  assign_modify_operation::do_generate_ax (struct expression *exp,
   if (subop->opcode () != OP_INTERNALVAR)
     error (_("May only assign to trace state variables"));
 
-  internalvar_operation *ivarop
-    = gdb::checked_static_cast<internalvar_operation *> (subop);
-
-  const char *name = internalvar_name (ivarop->get_internalvar ());
+  const char *name = internalvar_op_name (subop);
   struct trace_state_variable *tsv;
 
   tsv = find_trace_state_variable (name);
diff --git a/gdb/cli/cli-utils.c b/gdb/cli/cli-utils.c
index 45b30842e..7dedb3829 100644
--- a/gdb/cli/cli-utils.c
+++ b/gdb/cli/cli-utils.c
@@ -49,7 +49,7 @@  get_ulongest (const char **pp, int trailer)
 	  while (isalnum (*p) || *p == '_')
 	    p++;
 	  std::string varname (start, p - start);
-	  if (!get_internalvar_integer (lookup_internalvar (varname.c_str ()),
+	  if (!get_internalvar_integer (lookup_only_internalvar (varname.c_str ()),
 				       &retval))
 	    error (_("Convenience variable $%s does not have integer value."),
 		   varname.c_str ());
diff --git a/gdb/expop.h b/gdb/expop.h
index 2d46a9dad..810097519 100644
--- a/gdb/expop.h
+++ b/gdb/expop.h
@@ -878,6 +878,42 @@  class bool_operation
   { return true; }
 };
 
+/* Reference to a variable that had not been defined at parse time.  */
+class uninit_internalvar_operation
+  : public tuple_holding_operation<std::string>
+{
+public:
+
+  using tuple_holding_operation::tuple_holding_operation;
+
+  value *evaluate (struct type *expect_type,
+		   struct expression *exp,
+		   enum noside noside) override
+  {
+    internalvar *iv = lookup_only_internalvar (std::get<0> (m_storage).c_str ());
+    if (iv == nullptr)
+      return value::allocate (builtin_type (exp->gdbarch)->builtin_void);
+
+    return value_of_internalvar (exp->gdbarch, iv);
+  }
+
+  const char *get_name () const
+  {
+    return std::get<0> (m_storage).c_str ();
+  }
+
+  enum exp_opcode opcode () const override
+  { return OP_INTERNALVAR; }
+
+protected:
+
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override;
+};
+
 class internalvar_operation
   : public tuple_holding_operation<internalvar *>
 {
@@ -1891,7 +1927,16 @@  class assign_operation
 		   struct expression *exp,
 		   enum noside noside) override
   {
-    value *lhs = std::get<0> (m_storage)->evaluate (nullptr, exp, noside);
+    operation *lhs_op = std::get<0> (m_storage).get ();
+
+    /* If the operation is an internalvar that was not initialized at
+       parse time, ensure that it exists. */
+    auto *uninit_var_op = dynamic_cast<uninit_internalvar_operation *> (lhs_op);
+    if (uninit_var_op != nullptr)
+      lookup_internalvar (uninit_var_op->get_name ());
+
+    value *lhs = lhs_op->evaluate (nullptr, exp, noside);
+
     /* Special-case assignments where the left-hand-side is a
        convenience variable -- in these, don't bother setting an
        expected type.  This avoids a weird case where re-assigning a
@@ -1940,6 +1985,14 @@  class assign_modify_operation
 		   struct expression *exp,
 		   enum noside noside) override
   {
+    operation *lhs_op = std::get<1> (m_storage).get ();
+
+    /* If the operation is an internalvar that was not initialized at
+       parse time, ensure that it exists. */
+    auto *uninit_var_op = dynamic_cast<uninit_internalvar_operation *> (lhs_op);
+    if (uninit_var_op != nullptr)
+      lookup_internalvar (uninit_var_op->get_name ());
+
     value *lhs = std::get<1> (m_storage)->evaluate (nullptr, exp, noside);
     value *rhs = std::get<2> (m_storage)->evaluate (expect_type, exp, noside);
     return eval_binop_assign_modify (expect_type, exp, noside,
diff --git a/gdb/parse.c b/gdb/parse.c
index e0837de7b..b6327956e 100644
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -240,10 +240,9 @@  parser_state::push_dollar (struct stoken str)
       return;
     }
 
-  /* Any other names are assumed to be debugger internal variables.  */
-
-  push_new<expr::internalvar_operation>
-    (create_internalvar (copy.c_str () + 1));
+  /* Any other names are assumed to be debugger internal variables which
+     have not yet been initialized.  */
+  push_new<expr::uninit_internalvar_operation> (copy.c_str () + 1);
 }
 
 /* See parser-defs.h.  */