gdb: refactor the non-printing disassemblers

This commit started from an observation I made while working on some
other disassembler patches, that is, that the function
gdb_buffered_insn_length, is broken ... sort of.

I noticed that the gdb_buffered_insn_length function doesn't set up
the application data field if the disassemble_info structure.

Further, I noticed that some architectures, for example, ARM, require
that the application_data field be set, see gdb_print_insn_arm in
arm-tdep.c.

And so, if we ever use gdb_buffered_insn_length for ARM, then GDB will
likely crash.  Which is why I said only "sort of" broken.  Right now
we don't use gdb_buffered_insn_length with ARM, so maybe it isn't
broken yet?

Anyway to prove to myself that there was a problem here I extended the
disassembler self tests in disasm-selftests.c to include a test of
gdb_buffered_insn_length.  As I run the test for all architectures, I
do indeed see GDB crash for ARM.

To fix this we need gdb_buffered_insn_length to create a disassembler
that inherits from gdb_disassemble_info, but we also need this new
disassembler to not print anything.

And so, I introduce a new gdb_non_printing_disassembler class, this is
a disassembler that doesn't print anything to the output stream.

I then observed that both ARC and S12Z also create non-printing
disassemblers, but these are slightly different.  While the
disassembler in gdb_non_printing_disassembler reads the instruction
from a buffer, the ARC and S12Z disassemblers read from target memory
using target_read_code.

And so, I further split gdb_non_printing_disassembler into two
sub-classes, gdb_non_printing_memory_disassembler and
gdb_non_printing_buffer_disassembler.

The new selftests now pass, but otherwise, there should be no user
visible changes after this commit.

1 files changed, 2 insertions, 24 deletions

diff --git a/gdb/s12z-tdep.c b/gdb/s12z-tdep.c
index 5394c1b..4e33faa 100644
--- a/gdb/s12z-tdep.c
+++ b/gdb/s12z-tdep.c
@@ -141,27 +141,6 @@ s12z_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int num)
 
 /* Support functions for frame handling.  */
 
-
-/* Return a disassemble_info initialized for s12z disassembly, however,
-   the disassembler will not actually print anything.  */
-
-static struct disassemble_info
-s12z_disassemble_info (struct gdbarch *gdbarch)
-{
-  struct disassemble_info di;
-  init_disassemble_info_for_no_printing (&di);
-  di.arch = gdbarch_bfd_arch_info (gdbarch)->arch;
-  di.mach = gdbarch_bfd_arch_info (gdbarch)->mach;
-  di.endian = gdbarch_byte_order (gdbarch);
-  di.read_memory_func = [](bfd_vma memaddr, gdb_byte *myaddr,
-			   unsigned int len, struct disassemble_info *info)
-    {
-      return target_read_code (memaddr, myaddr, len);
-    };
-  return di;
-}
-
-
 /* A struct (based on mem_read_abstraction_base) to read memory
    through the disassemble_info API.  */
 struct mem_read_abstraction
@@ -332,15 +311,14 @@ s12z_frame_cache (struct frame_info *this_frame, void **prologue_cache)
   int frame_size = 0;
   int saved_frame_size = 0;
 
-  struct disassemble_info di = s12z_disassemble_info (gdbarch);
-
+  struct gdb_non_printing_memory_disassembler dis (gdbarch);
 
   struct mem_read_abstraction mra;
   mra.base.read = (int (*)(mem_read_abstraction_base*,
 			   int, size_t, bfd_byte*)) abstract_read_memory;
   mra.base.advance = advance ;
   mra.base.posn = posn;
-  mra.info = &di;
+  mra.info = dis.disasm_info ();
 
   while (this_pc > addr)
     {