binutils-gdb/gdb/disasm.h
Simon Marchi e0700ba44c gdb: make string-like set show commands use std::string variable
String-like settings (var_string, var_filename, var_optional_filename,
var_string_noescape) currently take a pointer to a `char *` storage
variable (typically global) that holds the setting's value.  I'd like to
"mordernize" this by changing them to use an std::string for storage.

An obvious reason is that string operations on std::string are often
easier to write than with C strings.  And they avoid having to do any
manual memory management.

Another interesting reason is that, with `char *`, nullptr and an empty
string often both have the same meaning of "no value".  String settings
are initially nullptr (unless initialized otherwise).  But when doing
"set foo" (where `foo` is a string setting), the setting now points to
an empty string.  For example, solib_search_path is nullptr at startup,
but points to an empty string after doing "set solib-search-path".  This
leads to some code that needs to check for both to check for "no value".
Or some code that converts back and forth between NULL and "" when
getting or setting the value.  I find this very error-prone, because it
is very easy to forget one or the other.  With std::string, we at least
know that the variable is not "NULL".  There is only one way of
representing an empty string setting, that is with an empty string.

I was wondering whether the distinction between NULL and "" would be
important for some setting, but it doesn't seem so.  If that ever
happens, it would be more C++-y and self-descriptive to use
optional<string> anyway.

Actually, there's one spot where this distinction mattered, it's in
init_history, for the test gdb.base/gdbinit-history.exp.  init_history
sets the history filename to the default ".gdb_history" if it sees that
the setting was never set - if history_filename is nullptr.  If
history_filename is an empty string, it means the setting was explicitly
cleared, so it leaves it as-is.  With the change to std::string, this
distinction doesn't exist anymore.  This can be fixed by moving the code
that chooses a good default value for history_filename to
_initialize_top.  This is ran before -ex commands are processed, so an
-ex command can then clear that value if needed (what
gdb.base/gdbinit-history.exp tests).

Another small improvement, in my opinion is that we can now easily
give string parameters initial values, by simply initializing the global
variables, instead of xstrdup-ing it in the _initialize function.

In Python and Guile, when registering a string-like parameter, we
allocate (with new) an std::string that is owned by the param_smob (in
Guile) and the parmpy_object (in Python) objects.

This patch started by changing all relevant add_setshow_* commands to
take an `std::string *` instead of a `char **` and fixing everything
that failed to build.  That includes of course all string setting
variable and their uses.

string_option_def now uses an std::string also, because there's a
connection between options and settings (see
add_setshow_cmds_for_options).

The add_path function in source.c is really complex and twisted, I'd
rather not try to change it to work on an std::string right now.
Instead, I added an overload that copies the std:string to a `char *`
and back.  This means more copying, but this is not used in a hot path
at all, so I think it is acceptable.

Change-Id: I92c50a1bdd8307141cdbacb388248e4e4fc08c93
Co-authored-by: Lancelot SIX <lsix@lancelotsix.com>
2021-10-03 17:53:16 +01:00

169 lines
5.1 KiB
C++

/* Disassemble support for GDB.
Copyright (C) 2002-2021 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 DISASM_H
#define DISASM_H
#include "dis-asm.h"
#include "gdbsupport/enum-flags.h"
enum gdb_disassembly_flag
{
DISASSEMBLY_SOURCE_DEPRECATED = (0x1 << 0),
DISASSEMBLY_RAW_INSN = (0x1 << 1),
DISASSEMBLY_OMIT_FNAME = (0x1 << 2),
DISASSEMBLY_FILENAME = (0x1 << 3),
DISASSEMBLY_OMIT_PC = (0x1 << 4),
DISASSEMBLY_SOURCE = (0x1 << 5),
DISASSEMBLY_SPECULATIVE = (0x1 << 6),
};
DEF_ENUM_FLAGS_TYPE (enum gdb_disassembly_flag, gdb_disassembly_flags);
struct gdbarch;
struct ui_out;
struct ui_file;
class gdb_disassembler
{
using di_read_memory_ftype = decltype (disassemble_info::read_memory_func);
public:
gdb_disassembler (struct gdbarch *gdbarch, struct ui_file *file)
: gdb_disassembler (gdbarch, file, dis_asm_read_memory)
{}
~gdb_disassembler ();
DISABLE_COPY_AND_ASSIGN (gdb_disassembler);
int print_insn (CORE_ADDR memaddr, int *branch_delay_insns = NULL);
/* Return the gdbarch of gdb_disassembler. */
struct gdbarch *arch ()
{ return m_gdbarch; }
protected:
gdb_disassembler (struct gdbarch *gdbarch, struct ui_file *file,
di_read_memory_ftype func);
struct ui_file *stream ()
{ return (struct ui_file *) m_di.stream; }
private:
struct gdbarch *m_gdbarch;
/* Stores data required for disassembling instructions in
opcodes. */
struct disassemble_info m_di;
/* If we own the string in `m_di.disassembler_options', we do so
using this field. */
std::string m_disassembler_options_holder;
CORE_ADDR m_err_memaddr;
static int dis_asm_read_memory (bfd_vma memaddr, gdb_byte *myaddr,
unsigned int len,
struct disassemble_info *info);
static void dis_asm_memory_error (int err, bfd_vma memaddr,
struct disassemble_info *info);
static void dis_asm_print_address (bfd_vma addr,
struct disassemble_info *info);
};
/* An instruction to be disassembled. */
struct disasm_insn
{
/* The address of the memory containing the instruction. */
CORE_ADDR addr;
/* An optional instruction number. If non-zero, it is printed first. */
unsigned int number;
/* True if the instruction was executed speculatively. */
unsigned int is_speculative:1;
};
extern void gdb_disassembly (struct gdbarch *gdbarch, struct ui_out *uiout,
gdb_disassembly_flags flags, int how_many,
CORE_ADDR low, CORE_ADDR high);
/* Print the instruction at address MEMADDR in debugged memory,
on STREAM. Returns the length of the instruction, in bytes,
and, if requested, the number of branch delay slot instructions. */
extern int gdb_print_insn (struct gdbarch *gdbarch, CORE_ADDR memaddr,
struct ui_file *stream, int *branch_delay_insns);
/* Class used to pretty-print instructions. */
class gdb_pretty_print_disassembler
{
public:
explicit gdb_pretty_print_disassembler (struct gdbarch *gdbarch,
struct ui_out *uiout)
: m_uiout (uiout),
m_insn_stb (uiout->can_emit_style_escape ()),
m_di (gdbarch, &m_insn_stb)
{}
/* Prints the instruction INSN into the saved ui_out and returns the
length of the printed instruction in bytes. */
int pretty_print_insn (const struct disasm_insn *insn,
gdb_disassembly_flags flags);
private:
/* Returns the architecture used for disassembling. */
struct gdbarch *arch () { return m_di.arch (); }
/* The ui_out that is used by pretty_print_insn. */
struct ui_out *m_uiout;
/* The buffer used to build the instruction string. The
disassembler is initialized with this stream. */
string_file m_insn_stb;
/* The disassembler used for instruction printing. */
gdb_disassembler m_di;
/* The buffer used to build the raw opcodes string. */
string_file m_opcode_stb;
};
/* Return the length in bytes of the instruction at address MEMADDR in
debugged memory. */
extern int gdb_insn_length (struct gdbarch *gdbarch, CORE_ADDR memaddr);
/* Return the length in bytes of INSN, originally at MEMADDR. MAX_LEN
is the size of the buffer containing INSN. */
extern int gdb_buffered_insn_length (struct gdbarch *gdbarch,
const gdb_byte *insn, int max_len,
CORE_ADDR memaddr);
/* Returns GDBARCH's disassembler options. */
extern char *get_disassembler_options (struct gdbarch *gdbarch);
/* Sets the active gdbarch's disassembler options to OPTIONS. */
extern void set_disassembler_options (const char *options);
#endif