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gdb: have gdb_disassemble_info carry 'this' in its stream pointer

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The gdb_disassemble_info class is a wrapper around the libopcodes
disassemble_info struct.  The 'stream' field of disassemble_info is
passed as an argument to the fprintf_func and fprintf_styled_func
callbacks when the disassembler wants to print anything.

Previously, GDB would store a pointer to a ui_file object in the
'stream' field, then, when the disassembler wanted to print anything,
the content would be written to the ui_file object.  An example of an
fprintf_func callback, from gdb/disasm.c is:

  int
  gdb_disassembler::dis_asm_fprintf (void *stream, const char *format, ...)
  {
    /* Write output to STREAM here.  */
  }

This is fine, but has one limitation, within the print callbacks we
only have access to STREAM, we can't access any additional state
stored within the gdb_disassemble_info object.

Right now this isn't a problem, but in a future commit this will
become an issue, how we style the output being written to STREAM will
depend on the state of the gdb_disassemble_info object, and this state
might need to be updated, depending on what is being printed.

In this commit I propose changing the 'stream' field of the
disassemble_info to carry a pointer to the gdb_disassemble_info
sub-class, rather than the stream itself.

We then have the two sub-classes of gdb_disassemble_info to consider,
the gdb_non_printing_disassembler class never cared about the stream,
previously, for this class, the stream was nullptr.  With the change
to make stream be a gdb_disassemble_info pointer, no further updates
are needed for gdb_non_printing_disassembler.

The other sub-class is gdb_printing_disassembler.  In this case the
sub-class now carries around a pointer to the stream object.  The
print callbacks are updated to cast the incoming stream object back to
a gdb_printing_disassembler, and then extract the stream.

This is purely a refactoring commit.  A later commit will add
additional state to the gdb_printing_disassembler, and update the
print callbacks to access this state.

There should be no user visible changes after this commit.
This commit is contained in:
Andrew Burgess 2022-04-05 11:06:16 +01:00
parent 53a7a7e17c
commit 81384924cd
2 changed files with 66 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
gdb/disasm.c
View File

@ -163,17 +163,33 @@ gdb_disassembler::dis_asm_print_address (bfd_vma addr,
print_address (self->arch (), addr, self->stream ());
}
/* See disasm.h. */
ui_file *
gdb_printing_disassembler::stream_from_gdb_disassemble_info (void *dis_info)
{
gdb_disassemble_info *di = (gdb_disassemble_info *) dis_info;
gdb_printing_disassembler *dis
= dynamic_cast<gdb_printing_disassembler *> (di);
gdb_assert (dis != nullptr);
ui_file *stream = dis->stream ();
gdb_assert (stream != nullptr);
return stream;
}
/* Format disassembler output to STREAM. */
int
gdb_printing_disassembler::fprintf_func (void *stream,
gdb_printing_disassembler::fprintf_func (void *dis_info,
const char *format, ...)
{
va_list args;
ui_file *stream = stream_from_gdb_disassemble_info (dis_info);
va_list args;
va_start (args, format);
gdb_vprintf ((struct ui_file *) stream, format, args);
gdb_vprintf (stream, format, args);
va_end (args);
/* Something non -ve. */
return 0;
}
@ -181,14 +197,15 @@ gdb_printing_disassembler::fprintf_func (void *stream,
/* See disasm.h. */
int
gdb_printing_disassembler::fprintf_styled_func (void *stream,
gdb_printing_disassembler::fprintf_styled_func (void *dis_info,
enum disassembler_style style,
const char *format, ...)
{
va_list args;
ui_file *stream = stream_from_gdb_disassemble_info (dis_info);
va_list args;
va_start (args, format);
gdb_vprintf ((struct ui_file *) stream, format, args);
gdb_vprintf (stream, format, args);
va_end (args);
/* Something non -ve. */
return 0;
@ -809,7 +826,7 @@ gdb_disassembler::gdb_disassembler (struct gdbarch *gdbarch,
/* See disasm.h. */
gdb_disassemble_info::gdb_disassemble_info
(struct gdbarch *gdbarch, struct ui_file *stream,
(struct gdbarch *gdbarch,
read_memory_ftype read_memory_func, memory_error_ftype memory_error_func,
print_address_ftype print_address_func, fprintf_ftype fprintf_func,
fprintf_styled_ftype fprintf_styled_func)
@ -817,7 +834,7 @@ gdb_disassemble_info::gdb_disassemble_info
{
gdb_assert (fprintf_func != nullptr);
gdb_assert (fprintf_styled_func != nullptr);
init_disassemble_info (&m_di, stream, fprintf_func,
init_disassemble_info (&m_di, (void *) this, fprintf_func,
fprintf_styled_func);
m_di.flavour = bfd_target_unknown_flavour;
@ -930,7 +947,7 @@ gdb_disassembler::print_insn (CORE_ADDR memaddr,
/* Push any disassemble output to the real destination stream. We do
this even if the disassembler reported failure (-1) as the
disassembler may have printed something to its output stream. */
m_di.fprintf_func (m_dest, "%s", m_buffer.c_str ());
gdb_printf (m_dest, "%s", m_buffer.c_str ());
/* If the disassembler failed then report an appropriate error. */
if (length < 0)

63
gdb/disasm.h
View File

@ -58,16 +58,14 @@ protected:
using fprintf_ftype = decltype (disassemble_info::fprintf_func);
using fprintf_styled_ftype = decltype (disassemble_info::fprintf_styled_func);
/* Constructor, many fields in m_di are initialized from GDBARCH. STREAM
is where the output of the disassembler will be written too, the
remaining arguments are function callbacks that are written into
m_di. Of these function callbacks FPRINTF_FUNC and
FPRINTF_STYLED_FUNC must not be nullptr. If READ_MEMORY_FUNC,
MEMORY_ERROR_FUNC, or PRINT_ADDRESS_FUNC are nullptr, then that field
within m_di is left with its default value (see the libopcodes
function init_disassemble_info for the defaults). */
/* Constructor, many fields in m_di are initialized from GDBARCH. The
remaining arguments are function callbacks that are written into m_di.
Of these function callbacks FPRINTF_FUNC and FPRINTF_STYLED_FUNC must
not be nullptr. If READ_MEMORY_FUNC, MEMORY_ERROR_FUNC, or
PRINT_ADDRESS_FUNC are nullptr, then that field within m_di is left
with its default value (see the libopcodes function
init_disassemble_info for the defaults). */
gdb_disassemble_info (struct gdbarch *gdbarch,
struct ui_file *stream,
read_memory_ftype read_memory_func,
memory_error_ftype memory_error_func,
print_address_ftype print_address_func,
@ -77,10 +75,6 @@ protected:
/* Destructor. */
virtual ~gdb_disassemble_info ();
/* The stream that disassembler output is being written too. */
struct ui_file *stream ()
{ return (struct ui_file *) m_di.stream; }
/* Stores data required for disassembling instructions in
opcodes. */
struct disassemble_info m_di;
@ -109,6 +103,10 @@ struct gdb_printing_disassembler : public gdb_disassemble_info
protected:
/* The stream that disassembler output is being written too. */
struct ui_file *stream ()
{ return m_stream; }
/* Constructor. All the arguments are just passed to the parent class.
We also add the two print functions to the arguments passed to the
parent. See gdb_disassemble_info for a description of how the
@ -118,22 +116,41 @@ protected:
read_memory_ftype read_memory_func,
memory_error_ftype memory_error_func,
print_address_ftype print_address_func)
: gdb_disassemble_info (gdbarch, stream, read_memory_func,
: gdb_disassemble_info (gdbarch, read_memory_func,
memory_error_func, print_address_func,
fprintf_func, fprintf_styled_func)
{ /* Nothing. */ }
fprintf_func, fprintf_styled_func),
m_stream (stream)
{
gdb_assert (stream != nullptr);
}
/* Callback used as the disassemble_info's fprintf_func callback, this
writes to STREAM, which will be m_di.stream. */
static int fprintf_func (void *stream, const char *format, ...)
/* Callback used as the disassemble_info's fprintf_func callback. The
DIS_INFO pointer is a pointer to a gdb_printing_disassembler object.
Content is written to the m_stream extracted from DIS_INFO. */
static int fprintf_func (void *dis_info, const char *format, ...)
ATTRIBUTE_PRINTF(2,3);
/* Callback used as the disassemble_info's fprintf_styled_func callback,
this writes to STREAM, which will be m_di.stream. */
static int fprintf_styled_func (void *stream,
/* Callback used as the disassemble_info's fprintf_styled_func callback.
The DIS_INFO pointer is a pointer to a gdb_printing_disassembler
object. Content is written to the m_stream extracted from DIS_INFO. */
static int fprintf_styled_func (void *dis_info,
enum disassembler_style style,
const char *format, ...)
ATTRIBUTE_PRINTF(3,4);
private:
/* When libopcodes calls the fprintf_func and fprintf_styled_func
callbacks, a 'void *' argument is passed. We arrange, through our
call to init_disassemble_info that this argument will be a pointer to
a gdb_disassemble_info sub-class, specifically, a
gdb_printing_disassembler pointer. This helper function casts
DIS_INFO to the correct type (with some asserts), and then returns the
m_stream member variable. */
static ui_file *stream_from_gdb_disassemble_info (void *dis_info);
/* The stream to which output should be sent. */
struct ui_file *m_stream;
};
/* A basic disassembler that doesn't actually print anything. */
@ -142,7 +159,7 @@ struct gdb_non_printing_disassembler : public gdb_disassemble_info
{
gdb_non_printing_disassembler (struct gdbarch *gdbarch,
read_memory_ftype read_memory_func)
: gdb_disassemble_info (gdbarch, nullptr /* stream */,
: gdb_disassemble_info (gdbarch,
read_memory_func,
nullptr /* memory_error_func */,
nullptr /* print_address_func */,