gdb: add new base class to gdb_disassembler

The motivation for this change is an upcoming Python disassembler API
that I would like to add.  As part of that change I need to create a
new disassembler like class that contains a disassemble_info and a
gdbarch.  The management of these two objects is identical to how we
manage these objects within gdb_disassembler, so it might be tempting
for my new class to inherit from gdb_disassembler.

The problem however, is that gdb_disassembler has a tight connection
between its constructor, and its print_insn method.  In the
constructor the ui_file* that is passed in is replaced with a member
variable string_file*, and then in print_insn, the contents of the
member variable string_file are printed to the original ui_file*.

What this means is that the gdb_disassembler class has a tight
coupling between its constructor and print_insn; the class just isn't
intended to be used in a situation where print_insn is not going to be
called, which is how my (upcoming) sub-class would need to operate.

My solution then, is to separate out the management of the
disassemble_info and gdbarch into a new gdb_disassemble_info class,
and make this class a parent of gdb_disassembler.

In arm-tdep.c and mips-tdep.c, where we used to cast the
disassemble_info->application_data to a gdb_disassembler, we can now
cast to a gdb_disassemble_info as we only need to access the gdbarch
information.

Now, my new Python disassembler sub-class will still want to print
things to an output stream, and so we will want access to the
dis_asm_fprintf functionality for printing.

However, rather than move this printing code into the
gdb_disassemble_info base class, I have added yet another level of
hierarchy, a gdb_printing_disassembler, thus the class structure is
now:

  struct gdb_disassemble_info {};
  struct gdb_printing_disassembler : public gdb_disassemble_info {};
  struct gdb_disassembler : public gdb_printing_disassembler {};

In a later commit my new Python disassembler will inherit from
gdb_printing_disassembler.

The reason for adding the additional layer to the class hierarchy is
that in yet another commit I intend to rewrite the function
gdb_buffered_insn_length, and to do this I will be creating yet more
disassembler like classes, however, these will not print anything,
thus I will add a gdb_non_printing_disassembler class that also
inherits from gdb_disassemble_info.  Knowing that that change is
coming, I've gone with the above class hierarchy now.

There should be no user visible changes after this commit.

1 files changed, 38 insertions, 20 deletions

diff --git a/gdb/disasm.c b/gdb/disasm.c
index f2df5ef..6ac8438 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -166,7 +166,8 @@ gdb_disassembler::dis_asm_print_address (bfd_vma addr,
 /* Format disassembler output to STREAM.  */
 
 int
-gdb_disassembler::dis_asm_fprintf (void *stream, const char *format, ...)
+gdb_printing_disassembler::fprintf_func (void *stream,
+					 const char *format, ...)
 {
   va_list args;
 
@@ -180,9 +181,9 @@ gdb_disassembler::dis_asm_fprintf (void *stream, const char *format, ...)
 /* See disasm.h.  */
 
 int
-gdb_disassembler::dis_asm_styled_fprintf (void *stream,
-					  enum disassembler_style style,
-					  const char *format, ...)
+gdb_printing_disassembler::fprintf_styled_func (void *stream,
+						enum disassembler_style style,
+						const char *format, ...)
 {
   va_list args;
 
@@ -797,26 +798,41 @@ get_all_disassembler_options (struct gdbarch *gdbarch)
 
 gdb_disassembler::gdb_disassembler (struct gdbarch *gdbarch,
 				    struct ui_file *file,
-				    di_read_memory_ftype read_memory_func)
-  : m_gdbarch (gdbarch),
+				    read_memory_ftype func)
+  : gdb_printing_disassembler (gdbarch, &m_buffer, func,
+			       dis_asm_memory_error, dis_asm_print_address),
     m_buffer (!use_ext_lang_colorization_p && disassembler_styling
 	      && file->can_emit_style_escape ()),
     m_dest (file)
+{ /* Nothing.  */ }
+
+/* See disasm.h.  */
+
+gdb_disassemble_info::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, fprintf_ftype fprintf_func,
+   fprintf_styled_ftype fprintf_styled_func)
+    : m_gdbarch (gdbarch)
 {
-  init_disassemble_info (&m_di, &m_buffer, dis_asm_fprintf,
-			 dis_asm_styled_fprintf);
+  gdb_assert (fprintf_func != nullptr);
+  gdb_assert (fprintf_styled_func != nullptr);
+  init_disassemble_info (&m_di, stream, fprintf_func,
+			 fprintf_styled_func);
   m_di.flavour = bfd_target_unknown_flavour;
-  m_di.memory_error_func = dis_asm_memory_error;
-  m_di.print_address_func = dis_asm_print_address;
-  /* NOTE: cagney/2003-04-28: The original code, from the old Insight
-     disassembler had a local optimization here.  By default it would
-     access the executable file, instead of the target memory (there
-     was a growing list of exceptions though).  Unfortunately, the
-     heuristic was flawed.  Commands like "disassemble &variable"
-     didn't work as they relied on the access going to the target.
-     Further, it has been superseeded by trust-read-only-sections
-     (although that should be superseeded by target_trust..._p()).  */
-  m_di.read_memory_func = read_memory_func;
+
+  /* The memory_error_func, print_address_func, and read_memory_func are
+     all initialized to a default (non-nullptr) value by the call to
+     init_disassemble_info above.  If the user is overriding these fields
+     (by passing non-nullptr values) then do that now, otherwise, leave
+     these fields as the defaults.  */
+  if (memory_error_func != nullptr)
+    m_di.memory_error_func = memory_error_func;
+  if (print_address_func != nullptr)
+    m_di.print_address_func = print_address_func;
+  if (read_memory_func != nullptr)
+    m_di.read_memory_func = read_memory_func;
+
   m_di.arch = gdbarch_bfd_arch_info (gdbarch)->arch;
   m_di.mach = gdbarch_bfd_arch_info (gdbarch)->mach;
   m_di.endian = gdbarch_byte_order (gdbarch);
@@ -828,7 +844,9 @@ gdb_disassembler::gdb_disassembler (struct gdbarch *gdbarch,
   disassemble_init_for_target (&m_di);
 }
 
-gdb_disassembler::~gdb_disassembler ()
+/* See disasm.h.  */
+
+gdb_disassemble_info::~gdb_disassemble_info ()
 {
   disassemble_free_target (&m_di);
 }