gdb/extension.h

/* Interface between gdb and its extension languages.

   Copyright (C) 2014-2024 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef EXTENSION_H
#define EXTENSION_H

#include "mi/mi-cmds.h"
#include "gdbsupport/array-view.h"
#include "hashtab.h"
#include <optional>

struct breakpoint;
struct command_line;
class frame_info_ptr;
struct language_defn;
struct objfile;
struct extension_language_defn;
struct type;
struct ui_file;
struct ui_out;
struct value;
struct value_print_options;

/* A function to load and process a script file.
   The file has been opened and is ready to be read from the beginning.
   Any exceptions are not caught, and are passed to the caller.  */
typedef void script_sourcer_func (const struct extension_language_defn *,
				  FILE *stream, const char *filename);

/* A function to load and process a script for an objfile.
   The file has been opened and is ready to be read from the beginning.
   Any exceptions are not caught, and are passed to the caller.  */
typedef void objfile_script_sourcer_func
  (const struct extension_language_defn *,
   struct objfile *, FILE *stream, const char *filename);

/* A function to execute a script for an objfile.
   Any exceptions are not caught, and are passed to the caller.  */
typedef void objfile_script_executor_func
  (const struct extension_language_defn *,
   struct objfile *, const char *name, const char *script);

/* Enum of each extension(/scripting) language.  */

enum extension_language
  {
    EXT_LANG_NONE,
    EXT_LANG_GDB,
    EXT_LANG_PYTHON,
    EXT_LANG_GUILE
  };

/* Extension language frame-filter status return values.  */

enum ext_lang_bt_status
  {
    /* Return when an error has occurred in processing frame filters,
       or when printing the stack.  */
    EXT_LANG_BT_ERROR = -1,

    /* Return from internal routines to indicate that the function
       succeeded.  */
    EXT_LANG_BT_OK = 1,

    /* Return when the frame filter process is complete, but there
       were no filter registered and enabled to process.  */
    EXT_LANG_BT_NO_FILTERS = 2
  };

/* Flags to pass to apply_extlang_frame_filter.  */

enum frame_filter_flag
  {
    /* Set this flag if frame level is to be printed.  */
    PRINT_LEVEL = 1 << 0,

    /* Set this flag if frame information is to be printed.  */
    PRINT_FRAME_INFO = 1 << 1,

    /* Set this flag if frame arguments are to be printed.  */
    PRINT_ARGS = 1 << 2,

    /* Set this flag if frame locals are to be printed.  */
    PRINT_LOCALS = 1 << 3,

    /* Set this flag if a "More frames" message is to be printed.  */
    PRINT_MORE_FRAMES = 1 << 4,

    /* Set this flag if elided frames should not be printed.  */
    PRINT_HIDE = 1 << 5,

    /* Set this flag if pretty printers for frame arguments should not
       be invoked.  */
    PRINT_RAW_FRAME_ARGUMENTS = 1 << 6,
  };

DEF_ENUM_FLAGS_TYPE (enum frame_filter_flag, frame_filter_flags);

/* A choice of the different frame argument printing strategies that
   can occur in different cases of frame filter instantiation.  */

enum ext_lang_frame_args
  {
    /* Print no values for arguments when invoked from the MI. */
    NO_VALUES = PRINT_NO_VALUES,

    MI_PRINT_ALL_VALUES = PRINT_ALL_VALUES,

    /* Print only simple values (what MI defines as "simple") for
       arguments when invoked from the MI. */
    MI_PRINT_SIMPLE_VALUES = PRINT_SIMPLE_VALUES,

    /* Print only scalar values for arguments when invoked from the CLI. */
    CLI_SCALAR_VALUES,

    /* Print all values for arguments when invoked from the CLI. */
    CLI_ALL_VALUES,

    /* Only indicate the presence of arguments when invoked from the CLI.  */
    CLI_PRESENCE
  };

/* The possible results of
   extension_language_ops.breakpoint_cond_says_stop.  */

enum ext_lang_bp_stop
  {
    /* No "stop" condition is set.  */
    EXT_LANG_BP_STOP_UNSET,

    /* A "stop" condition is set, and it says "don't stop".  */
    EXT_LANG_BP_STOP_NO,

    /* A "stop" condition is set, and it says "stop".  */
    EXT_LANG_BP_STOP_YES
  };

/* Table of type printers associated with the global typedef table.  */

struct ext_lang_type_printers
{
  ext_lang_type_printers ();
  ~ext_lang_type_printers ();

  DISABLE_COPY_AND_ASSIGN (ext_lang_type_printers);

  /* Type-printers from Python.  */
  void *py_type_printers = nullptr;
};

/* The return code for some API calls.  */

enum ext_lang_rc
{
  /* The operation completed successfully.  */
  EXT_LANG_RC_OK,

  /* The operation was not performed (e.g., no pretty-printer).  */
  EXT_LANG_RC_NOP,

  /* There was an error (e.g., Python error while printing a value).
     When an error occurs no further extension languages are tried.
     This is to preserve existing behaviour, and because it's convenient
     for Python developers.
     Note: This is different than encountering a memory error trying to read
     a value for pretty-printing.  Here we're referring to, e.g., programming
     errors that trigger an exception in the extension language.  */
  EXT_LANG_RC_ERROR
};

/* A type which holds its extension language specific xmethod worker data.  */

struct xmethod_worker
{
  xmethod_worker (const extension_language_defn *extlang)
  : m_extlang (extlang)
  {}

  virtual ~xmethod_worker () = default;

  /* Invoke the xmethod encapsulated in this worker and return the result.
     The method is invoked on OBJ with arguments in the ARGS array.  */

  virtual value *invoke (value *obj, gdb::array_view<value *> args) = 0;

  /* Return the arg types of the xmethod encapsulated in this worker.
     The type of the 'this' object is returned as the first element of
     the vector.  */

  std::vector<type *> get_arg_types ();

  /* Return the type of the result of the xmethod encapsulated in this worker.
     OBJECT and ARGS are the same as for invoke.  */

  type *get_result_type (value *object, gdb::array_view<value *> args);

private:

  /* Return the types of the arguments the method takes.  The types
     are returned in TYPE_ARGS, one per argument.  */

  virtual enum ext_lang_rc do_get_arg_types
    (std::vector<type *> *type_args) = 0;

  /* Fetch the type of the result of the method implemented by this
     worker.  OBJECT and ARGS are the same as for the invoked method.
     The result type is stored in *RESULT_TYPE.  */

  virtual enum ext_lang_rc do_get_result_type
    (struct value *obj, gdb::array_view<value *> args,
     struct type **result_type_ptr) = 0;

  /* The language the xmethod worker is implemented in.  */

  const extension_language_defn *m_extlang;
};

typedef std::unique_ptr<xmethod_worker> xmethod_worker_up;

/* The interface for gdb's own extension(/scripting) language.  */
extern const struct extension_language_defn extension_language_gdb;

extern const struct extension_language_defn *get_ext_lang_defn
  (enum extension_language lang);

extern const struct extension_language_defn *get_ext_lang_of_file
  (const char *file);

extern int ext_lang_present_p (const struct extension_language_defn *);

extern int ext_lang_initialized_p (const struct extension_language_defn *);

extern void throw_ext_lang_unsupported
  (const struct extension_language_defn *);

/* Accessors for "public" attributes of the extension language definition.  */

extern enum extension_language ext_lang_kind
  (const struct extension_language_defn *);

extern const char *ext_lang_name (const struct extension_language_defn *);

extern const char *ext_lang_capitalized_name
  (const struct extension_language_defn *);

extern const char *ext_lang_suffix (const struct extension_language_defn *);

extern const char *ext_lang_auto_load_suffix
  (const struct extension_language_defn *);

extern script_sourcer_func *ext_lang_script_sourcer
  (const struct extension_language_defn *);

extern objfile_script_sourcer_func *ext_lang_objfile_script_sourcer
  (const struct extension_language_defn *);

extern objfile_script_executor_func *ext_lang_objfile_script_executor
  (const struct extension_language_defn *);

/* Return true if auto-loading of EXTLANG scripts is enabled.
   False is returned if support for this language isn't compiled in.  */

extern bool ext_lang_auto_load_enabled (const struct extension_language_defn *);

/* Wrappers for each extension language API function that iterate over all
   extension languages.  */

extern void ext_lang_initialization (void);

/* Shut down all extension languages.  */
extern void ext_lang_shutdown ();

extern void eval_ext_lang_from_control_command (struct command_line *cmd);

extern void auto_load_ext_lang_scripts_for_objfile (struct objfile *);

extern gdb::unique_xmalloc_ptr<char> apply_ext_lang_type_printers
     (struct ext_lang_type_printers *, struct type *);

extern int apply_ext_lang_val_pretty_printer
  (struct value *value, struct ui_file *stream, int recurse,
   const struct value_print_options *options,
   const struct language_defn *language);

extern enum ext_lang_bt_status apply_ext_lang_frame_filter
  (const frame_info_ptr &frame, frame_filter_flags flags,
   enum ext_lang_frame_args args_type,
   struct ui_out *out, int frame_low, int frame_high);

extern void preserve_ext_lang_values (struct objfile *, htab_t copied_types);

extern const struct extension_language_defn *get_breakpoint_cond_ext_lang
  (struct breakpoint *b, enum extension_language skip_lang);

extern bool breakpoint_ext_lang_cond_says_stop (struct breakpoint *);

/* If a method with name METHOD_NAME is to be invoked on an object of type
   TYPE, then all extension languages are searched for implementations of
   methods with name METHOD_NAME.  All matches found are appended to the WORKERS
   vector.  */

extern void get_matching_xmethod_workers
  (struct type *type, const char *method_name,
   std::vector<xmethod_worker_up> *workers);

/* Try to colorize some source code.  FILENAME is the name of the file
   holding the code.  CONTENTS is the source code itself.  This will
   either a colorized (using ANSI terminal escapes) version of the
   source code, or an empty value if colorizing could not be done.  */

extern std::optional<std::string> ext_lang_colorize
  (const std::string &filename, const std::string &contents);

/* Try to colorize a single line of disassembler output, CONTENT for
   GDBARCH.  This will return either a colorized (using ANSI terminal
   escapes) version of CONTENT, or an empty value if colorizing could not
   be done.  */

extern std::optional<std::string> ext_lang_colorize_disasm
  (const std::string &content, gdbarch *gdbarch);

/* Calls extension_language_ops::print_insn for each extension language,
   returning the result from the first extension language that returns a
   non-empty result (any further extension languages are not then called).

   All arguments are forwarded to extension_language_ops::print_insn, see
   that function for a full description.  */

extern std::optional<int> ext_lang_print_insn
  (struct gdbarch *gdbarch, CORE_ADDR address, struct disassemble_info *info);

/* When GDB calls into an extension language because an objfile was
   discovered for which GDB couldn't find any debug information, this
   structure holds the result that the extension language returns.

   There are three possible actions that might be returned by an extension;
   first an extension can return a filename, this is the path to the file
   containing the required debug  information.  The second possibility is
   to return a flag indicating that GDB should check again for the missing
   debug information, this would imply that the extension has installed
   the debug information into a location where GDB can be expected to find
   it.  And the third option is for the extension to just return a null
   result, indication there is nothing the extension can do to provide the
   missing debug information.  */
struct ext_lang_missing_debuginfo_result
{
  /* Default result.  The extension was unable to provide the missing debug
     info.  */
  ext_lang_missing_debuginfo_result ()
  { /* Nothing.  */ }

  /* When TRY_AGAIN is true GDB should try searching again, the extension
     may have installed the missing debug info into a suitable location.
     When TRY_AGAIN is false this is equivalent to the default, no
     argument, constructor.  */
  ext_lang_missing_debuginfo_result (bool try_again)
    : m_try_again (try_again)
  { /* Nothing.  */ }

  /* Look in FILENAME for the missing debug info.  */
  ext_lang_missing_debuginfo_result (std::string &&filename)
    : m_filename (std::move (filename))
  { /* Nothing.  */ }

  /* The filename where GDB can find the missing debuginfo.  This is empty
     if the extension didn't suggest a file that can be used.  */
  const std::string &
  filename () const
  {
    return m_filename;
  }

  /* Returns true if GDB should look again for the debug information.  */
  const bool
  try_again () const
  {
    return m_try_again;
  }

private:
  /* The filename where the missing debuginfo can now be found.  */
  std::string m_filename;

  /* When true GDB will search again for the debuginfo using its standard
     techniques.  When false GDB will not search again.  */
  bool m_try_again = false;
};

/* Called when GDB failed to find any debug information for OBJFILE.  */

extern ext_lang_missing_debuginfo_result ext_lang_handle_missing_debuginfo
  (struct objfile *objfile);

#if GDB_SELF_TEST
namespace selftests {
extern void (*hook_set_active_ext_lang) ();
}
#endif

/* Temporarily disable cooperative SIGINT handling.  Needed when we
   don't want a SIGINT to interrupt the currently active extension
   language.  */
class scoped_disable_cooperative_sigint_handling
{
public:
  scoped_disable_cooperative_sigint_handling ();
  ~scoped_disable_cooperative_sigint_handling ();

  DISABLE_COPY_AND_ASSIGN (scoped_disable_cooperative_sigint_handling);

private:
  struct active_ext_lang_state *m_prev_active_ext_lang_state;
  bool m_prev_cooperative_sigint_handling_disabled;
};

/* GDB's SIGINT handler basically sets a flag; code that might take a
   long time before it gets back to the event loop, and which ought to
   be interruptible, checks this flag using the QUIT macro, which, if
   GDB has the terminal, throws a quit exception.

   In addition to setting a flag, the SIGINT handler also marks a
   select/poll-able file descriptor as read-ready.  That is used by
   interruptible_select in order to support interrupting blocking I/O
   in a race-free manner.

   These functions use the extension_language_ops API to allow extension
   language(s) and GDB SIGINT handling to coexist seamlessly.  */

/* Return true if the quit flag has been set, false otherwise.
   Note: The flag is cleared as a side-effect.
   The flag is checked in all extension languages that support cooperative
   SIGINT handling, not just the current one.  This simplifies transitions.  */

extern bool check_quit_flag ();

/* Set the quit flag.
   This only sets the flag in the currently active extension language.
   If the currently active extension language does not have cooperative
   SIGINT handling, then GDB's global flag is set, and it is up to the
   extension language to call check_quit_flag.  The extension language
   is free to install its own SIGINT handler, but we still need to handle
   the transition.  */

extern void set_quit_flag ();

#endif /* EXTENSION_H */