Fix PR 20559 - "eval" command and $arg0...$arg9/$argc substitution

It'd be handy to be able to iterate over command arguments in
user-defined commands, in order to support optional arguments
($arg0..$argN).

I thought I could make it work with "eval", but alas, it doesn't work
currently.  E.g., with:

 define test
   set $i = 0
   while $i < $argc
     eval "print $arg%d", $i
     set $i = $i + 1
   end
 end

we get:

 (gdb) test 1
 $1 = void
 (gdb) test 1 2 3
 $2 = void
 $3 = void
 $4 = void
 (gdb)

The problem is that "eval" doesn't do user-defined command arguments
substitution after expanding its own argument.  This patch fixes that,
which makes the example above work:

 (gdb) test 1
 $1 = 1
 (gdb) test 1 2 3
 $2 = 1
 $3 = 2
 $4 = 3
 (gdb)

New test included, similar the above, but also exercises expanding
$argc.

I think this is likely to simplify many scripts out there, so I'm
adding an example to the manual and mentioning it in NEWS as well.

gdb/ChangeLog:
2016-12-02  Pedro Alves  <palves@redhat.com>

	PR cli/20559
	* NEWS: Mention "eval" expands user-defined command arguments.
	* cli/cli-script.c (execute_control_command): Adjust to rename.
	(insert_args): Rename to ...
	(insert_user_defined_cmd_args): ... this, and make extern.
	* cli/cli-script.h (insert_user_defined_cmd_args): New
	declaration.
	* printcmd.c: Include "cli/cli-script.h".
	(eval_command): Call insert_user_defined_cmd_args.

gdb/doc/ChangeLog:
2016-12-02  Pedro Alves  <palves@redhat.com>

	PR cli/20559
	* gdb.texinfo (Define): Add example of using "eval" to process a
	variable number of arguments.
	(Output) <eval>: Add anchor.

gdb/testsuite/ChangeLog:
2016-12-02  Pedro Alves  <palves@redhat.com>

	PR cli/20559
	* gdb.base/commands.exp (user_defined_command_args_eval): New
	procedure.
	(top level): Call it.

gdb/ChangeLog

@@ -1,3 +1,15 @@
+2016-12-02  Pedro Alves  <palves@redhat.com>
+
+	PR cli/20559
+	* NEWS: Mention "eval" expands user-defined command arguments.
+	* cli/cli-script.c (execute_control_command): Adjust to rename.
+	(insert_args): Rename to ...
+	(insert_user_defined_cmd_args): ... this, and make extern.
+	* cli/cli-script.h (insert_user_defined_cmd_args): New
+	declaration.
+	* printcmd.c: Include "cli/cli-script.h".
+	(eval_command): Call insert_user_defined_cmd_args.
+
 2016-12-02  Tom Tromey  <tom@tromey.com>
 
 	PR symtab/16264:

gdb/NEWS

@@ -32,6 +32,18 @@
 
 * Support for Java programs compiled with gcj has been removed.
 
+* The "eval" command now expands user-defined command arguments.
+
+  This makes it easier to process a variable number of arguments:
+
+   define mycommand
+     set $i = 0
+     while $i < $argc
+       eval "print $arg%d", $i
+       set $i = $i + 1
+     end
+   end
+
 * New targets
 
 Synopsys ARC			arc*-*-elf32

gdb/cli/cli-script.c

@@ -41,8 +41,6 @@ recurse_read_control_structure (char * (*read_next_line_func) (void),
 				void (*validator)(char *, void *),
 				void *closure);
 
-static std::string insert_args (const char *line);
-
 static struct cleanup * setup_user_args (char *p);
 
 static char *read_next_line (void);
@@ -455,7 +453,7 @@ execute_control_command (struct command_line *cmd)
     case simple_control:
       {
 	/* A simple command, execute it and return.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_defined_cmd_args (cmd->line);
 	execute_command (&new_line[0], 0);
 	ret = cmd->control_type;
 	break;
@@ -486,7 +484,7 @@ execute_control_command (struct command_line *cmd)
 	print_command_trace (buffer);
 
 	/* Parse the loop control expression for the while statement.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_defined_cmd_args (cmd->line);
 	expression_up expr = parse_expression (new_line.c_str ());
 
 	ret = simple_control;
@@ -551,7 +549,7 @@ execute_control_command (struct command_line *cmd)
 	print_command_trace (buffer);
 
 	/* Parse the conditional for the if statement.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_defined_cmd_args (cmd->line);
 	expression_up expr = parse_expression (new_line.c_str ());
 
 	current = NULL;
@@ -591,7 +589,7 @@ execute_control_command (struct command_line *cmd)
       {
 	/* Breakpoint commands list, record the commands in the
 	   breakpoint's command list and return.  */
-	std::string new_line = insert_args (cmd->line);
+	std::string new_line = insert_user_defined_cmd_args (cmd->line);
 	ret = commands_from_control_command (new_line.c_str (), cmd);
 	break;
       }
@@ -782,13 +780,12 @@ locate_arg (const char *p)
   return NULL;
 }
 
-/* Insert the user defined arguments stored in user_arg into the $arg
-   arguments found in line.  */
+/* See cli-script.h.  */
 
-static std::string
-insert_args (const char *line)
+std::string
+insert_user_defined_cmd_args (const char *line)
 {
-  /* If we are not in a user-defined function, treat $argc, $arg0, et
+  /* If we are not in a user-defined command, treat $argc, $arg0, et
      cetera as normal convenience variables.  */
   if (user_args == NULL)
     return line;

gdb/cli/cli-script.h

@@ -53,6 +53,12 @@ extern struct cleanup *
 
 extern void execute_user_command (struct cmd_list_element *c, char *args);
 
+/* If we're in a user-defined command, replace any $argc/$argN
+   reference found in LINE with the arguments that were passed to the
+   command.  Otherwise, treat $argc/$argN as normal convenience
+   variables.  */
+extern std::string insert_user_defined_cmd_args (const char *line);
+
 /* Exported to top.c */
 
 extern void print_command_trace (const char *cmd);

gdb/doc/ChangeLog

@@ -1,3 +1,10 @@
+2016-12-02  Pedro Alves  <palves@redhat.com>
+
+	PR cli/20559
+	* gdb.texinfo (Define): Add example of using "eval" to process a
+	variable number of arguments.
+	(Output) <eval>: Add anchor.
+
 2016-11-30  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* Makefile.in: Likewise.

gdb/doc/gdb.texinfo

@@ -24096,6 +24096,21 @@ define adder
 end
 @end smallexample
 
+Combining with the @code{eval} command (@pxref{eval}) makes it easier
+to process a variable number of arguments:
+
+@smallexample
+define adder
+  set $i = 0
+  set $sum = 0
+  while $i < $argc
+    eval "set $sum = $sum + $arg%d", $i
+    set $i = $i + 1
+  end
+  print $sum
+end
+@end smallexample
+
 @table @code
 
 @kindex define
@@ -24526,6 +24541,7 @@ Here's an example of printing DFP types using the above conversion letters:
 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
 @end smallexample
 
+@anchor{eval}
 @kindex eval
 @item eval @var{template}, @var{expressions}@dots{}
 Convert the values of one or more @var{expressions} under the control of

gdb/printcmd.c

@@ -45,6 +45,7 @@
 #include "charset.h"
 #include "arch-utils.h"
 #include "cli/cli-utils.h"
+#include "cli/cli-script.h"
 #include "format.h"
 #include "source.h"
 
@@ -2723,6 +2724,8 @@ eval_command (char *arg, int from_tty)
 
   std::string expanded = ui_file_as_string (ui_out);
 
+  expanded = insert_user_defined_cmd_args (expanded.c_str ());
+
   execute_command (&expanded[0], from_tty);
 
   do_cleanups (cleanups);

gdb/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2016-12-02  Pedro Alves  <palves@redhat.com>
+
+	PR cli/20559
+	* gdb.base/commands.exp (user_defined_command_args_eval): New
+	procedure.
+	(top level): Call it.
+
 2016-12-02  Luis Machado  <lgustavo@codesourcery.com>
 
 	* gdb.base/ovldbreak.exp (take_gdb_out_of_choice_menu): Restore

gdb/testsuite/gdb.base/commands.exp

@@ -352,6 +352,36 @@ proc_with_prefix user_defined_command_test {} {
 	"display user-defined empty command"
 }
 
+# Test that "eval" in a user-defined command expands $argc/$argN.
+
+proc_with_prefix user_defined_command_args_eval {} {
+    global gdb_prompt
+
+    gdb_test_multiple "define command_args_eval" \
+	"define command_args_eval" {
+	    -re "End with"  {
+		pass "define"
+	    }
+	}
+
+    # Make a command that constructs references to $argc and $argN via
+    # eval.
+    gdb_test \
+	[multi_line \
+	     {eval "printf \"argc = %%d,\", $arg%c", 'c'} \
+	     {set $i = 0} \
+	     {while $i < $argc} \
+	     {  eval "printf \" %%d\", $arg%d", $i} \
+	     {  set $i = $i + 1} \
+	     {end} \
+	     {printf "\n"} \
+	     {end}] \
+	"" \
+	"enter commands"
+
+    gdb_test "command_args_eval 1 2 3" "argc = 3, 1 2 3" "execute command"
+}
+
 proc_with_prefix watchpoint_command_test {} {
     global gdb_prompt
 
@@ -882,6 +912,7 @@ if_while_breakpoint_command_test
 infrun_breakpoint_command_test
 breakpoint_command_test
 user_defined_command_test
+user_defined_command_args_eval
 watchpoint_command_test
 test_command_prompt_position
 deprecated_command_test