Re: [PATCH v4 1/2] Add back gdb_pretty_print_insn

[Luis Machado <lgustavo@codesourcery.com>]

On 01/31/2017 06:30 PM, Pedro Alves wrote:
> ui_file_rewind is a ui_file method that only really works with mem
> buffer files, and is a nop on other ui_file types.  It'd be desirable
> to eliminate it from the base ui_file interface, and move it to the
> "mem_fileopen" subclass of ui_file instead.  A following patch does
> just that.
>
> Unfortunately, there are a couple references to ui_file_rewind inside
> gdb_disassembler::pretty_print_insn that were made harder to eliminate
> with the recent addition of the gdb_disassembler wrapper.
>
> Before the gdb_disassembler wrapper was added, in commit
> e47ad6c0bd7aa3 ("Refactor disassembly code"), gdb_pretty_print_insn
> used to be passed a ui_file pointer as argument, and it was simple to
> adjust that pointer be a "mem_fileopen" ui_file pointer instead, since
> there's only one gdb_pretty_print_insn caller.
>
> That commit made gdb_pretty_print_insn be a method of
> gdb_disassembler, and removed the method's ui_file parameter at the
> same time, replaced by referencing the gdb_disassembler's stream
> instead.  The trouble is that a gdb_disassembler can be instantiated
> with a pointer any kind of ui_file.  Casting the gdb_disassembler's
> stream to a mem_fileopen ui_file inside
> gdb_disassembler::pretty_print_insn in order to call the reset method
> would be gross hack.
>
> The fix here is to:
>
>  - make gdb_disassembler::pretty_print_insn a be free function again
>    instead of a method of gdb_disassembler.  I.e., bring back
>    gdb_pretty_print_insn.
>
>  - but, don't add back the ui_file * parameter.  We'd always be
>    passing in a fresh mem_fileopen anyway, so move the mem_fileopen
>    allocation inside.  That is a better interface, given that the
>    ui_file is only ever used as temporary scratch buffer as an
>    implementation detail of gdb_pretty_print_insn.  The function's
>    real "where to send output" parameter is the ui_out pointer.
>
>  - don't add back a disassemble_info pointer either.  That used to be
>    necessary for this bit:
>
> 	  err = m_di.read_memory_func (pc, &data, 1, &m_di);
> 	  if (err != 0)
> 	    m_di.memory_error_func (err, pc, &m_di);
>
>    ... but AFAIK, it's not really necessary.  We can replace those
>    three lines with a call to read_code.  This seems to fix a
>    regression even, because before commit d8b49cf0c891d0 ("Don't throw
>    exception in dis_asm_memory_error"), that memory_error_func call
>    would throw an error/exception, but now it only records the error
>    in the gdb_disassembler's m_err_memaddr field.  (read_code throws
>    on error.)
>
> With all these, gdb_pretty_print_insn is completely layered on top of
> gdb_disassembler only using the latter's public API.
>
> gdb/ChangeLog:
> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
>
> 	* disasm.c (gdb_disassembler::pretty_print_insn): Rename to
> 	...  (gdb_pretty_print_insn): ... this.  Now a free function.
> 	Add back a 'gdbarch' parameter.  Allocate a mem_fileopen
> 	stream here.  Adjust to call gdb_print_insn instead of
> 	gdb_disassembler::print_insn.
> 	(dump_insns, do_mixed_source_and_assembly_deprecated)
> 	(do_mixed_source_and_assembly, do_assembly_only): Add back a
> 	'gdbarch' parameter.  Remove gdb_disassembler parameter.
> 	(gdb_disassembly): Don't allocate a gdb_disassembler here.
> 	* disasm.h (gdb_disassembler::pretty_print_insn): Delete
> 	declaration.
> 	(gdb_pretty_print_insn): Re-add declaration.
> 	* record-btrace.c (btrace_insn_history): Don't allocate a
> 	gdb_disassembler here.  Adjust to call gdb_pretty_print_insn.
> ---
>  gdb/disasm.c        | 54 ++++++++++++++++++++++-------------------------------
>  gdb/disasm.h        | 11 ++++++-----
>  gdb/record-btrace.c |  8 ++------
>  3 files changed, 30 insertions(+), 43 deletions(-)
>
> diff --git a/gdb/disasm.c b/gdb/disasm.c
> index 897f2f1..59ebef0 100644
> --- a/gdb/disasm.c
> +++ b/gdb/disasm.c
> @@ -182,9 +182,9 @@ compare_lines (const void *mle1p, const void *mle2p)
>  /* See disasm.h.  */
>
>  int
> -gdb_disassembler::pretty_print_insn (struct ui_out *uiout,
> -				     const struct disasm_insn *insn,
> -				     int flags)
> +gdb_pretty_print_insn (struct gdbarch *gdbarch, struct ui_out *uiout,
> +		       const struct disasm_insn *insn,
> +		       int flags)
>  {
>    /* parts of the symbolic representation of the address */
>    int unmapped;
> @@ -195,8 +195,6 @@ gdb_disassembler::pretty_print_insn (struct ui_out *uiout,
>    char *filename = NULL;
>    char *name = NULL;
>    CORE_ADDR pc;
> -  struct ui_file *stb = stream ();
> -  struct gdbarch *gdbarch = arch ();
>
>    ui_out_chain = make_cleanup_ui_out_tuple_begin_end (uiout, NULL);
>    pc = insn->addr;
> @@ -250,7 +248,9 @@ gdb_disassembler::pretty_print_insn (struct ui_out *uiout,
>    if (name != NULL)
>      xfree (name);
>
> -  ui_file_rewind (stb);
> +  struct ui_file *stb = mem_fileopen ();
> +  make_cleanup_ui_file_delete (stb);
> +
>    if (flags & DISASSEMBLY_RAW_INSN)
>      {
>        CORE_ADDR end_pc;
> @@ -264,14 +264,12 @@ gdb_disassembler::pretty_print_insn (struct ui_out *uiout,
>        struct cleanup *cleanups =
>  	make_cleanup_ui_file_delete (opcode_stream);
>
> -      size = print_insn (pc);
> +      size = gdb_print_insn (gdbarch, pc, stb, NULL);
>        end_pc = pc + size;
>
>        for (;pc < end_pc; ++pc)
>  	{
> -	  err = m_di.read_memory_func (pc, &data, 1, &m_di);
> -	  if (err != 0)
> -	    m_di.memory_error_func (err, pc, &m_di);
> +	  read_code (pc, &data, 1);
>  	  fprintf_filtered (opcode_stream, "%s%02x",
>  			    spacer, (unsigned) data);
>  	  spacer = " ";
> @@ -283,10 +281,9 @@ gdb_disassembler::pretty_print_insn (struct ui_out *uiout,
>        do_cleanups (cleanups);
>      }
>    else
> -    size = print_insn (pc);
> +    size = gdb_print_insn (gdbarch, pc, stb, NULL);
>
>    uiout->field_stream ("inst", stb);
> -  ui_file_rewind (stb);
>    do_cleanups (ui_out_chain);
>    uiout->text ("\n");
>
> @@ -294,10 +291,9 @@ gdb_disassembler::pretty_print_insn (struct ui_out *uiout,
>  }
>
>  static int
> -dump_insns (struct ui_out *uiout, gdb_disassembler *di,
> -	    CORE_ADDR low, CORE_ADDR high,
> -	    int how_many, int flags,
> -	    CORE_ADDR *end_pc)
> +dump_insns (struct gdbarch *gdbarch,
> +	    struct ui_out *uiout, CORE_ADDR low, CORE_ADDR high,
> +	    int how_many, int flags, CORE_ADDR *end_pc)
>  {
>    struct disasm_insn insn;
>    int num_displayed = 0;
> @@ -309,7 +305,7 @@ dump_insns (struct ui_out *uiout, gdb_disassembler *di,
>      {
>        int size;
>
> -      size = di->pretty_print_insn (uiout, &insn, flags);
> +      size = gdb_pretty_print_insn (gdbarch, uiout, &insn, flags);
>        if (size <= 0)
>  	break;
>
> @@ -335,8 +331,8 @@ dump_insns (struct ui_out *uiout, gdb_disassembler *di,
>
>  static void
>  do_mixed_source_and_assembly_deprecated
> -  (struct ui_out *uiout,
> -   gdb_disassembler *di, struct symtab *symtab,
> +  (struct gdbarch *gdbarch, struct ui_out *uiout,
> +   struct symtab *symtab,
>     CORE_ADDR low, CORE_ADDR high,
>     int how_many, int flags)
>  {
> @@ -471,7 +467,7 @@ do_mixed_source_and_assembly_deprecated
>  	    = make_cleanup_ui_out_list_begin_end (uiout, "line_asm_insn");
>  	}
>
> -      num_displayed += dump_insns (uiout, di,
> +      num_displayed += dump_insns (gdbarch, uiout,
>  				   mle[i].start_pc, mle[i].end_pc,
>  				   how_many, flags, NULL);
>
> @@ -499,7 +495,6 @@ do_mixed_source_and_assembly_deprecated
>  static void
>  do_mixed_source_and_assembly (struct gdbarch *gdbarch,
>  			      struct ui_out *uiout,
> -			      gdb_disassembler *di,
>  			      struct symtab *main_symtab,
>  			      CORE_ADDR low, CORE_ADDR high,
>  			      int how_many, int flags)
> @@ -721,7 +716,7 @@ do_mixed_source_and_assembly (struct gdbarch *gdbarch,
>  	end_pc = std::min (sal.end, high);
>        else
>  	end_pc = pc + 1;
> -      num_displayed += dump_insns (uiout, di, pc, end_pc,
> +      num_displayed += dump_insns (gdbarch, uiout, pc, end_pc,
>  				   how_many, flags, &end_pc);
>        pc = end_pc;
>
> @@ -736,8 +731,7 @@ do_mixed_source_and_assembly (struct gdbarch *gdbarch,
>  }
>
>  static void
> -do_assembly_only (struct ui_out *uiout,
> -		  gdb_disassembler *di,
> +do_assembly_only (struct gdbarch *gdbarch, struct ui_out *uiout,
>  		  CORE_ADDR low, CORE_ADDR high,
>  		  int how_many, int flags)
>  {
> @@ -745,7 +739,7 @@ do_assembly_only (struct ui_out *uiout,
>
>    ui_out_chain = make_cleanup_ui_out_list_begin_end (uiout, "asm_insns");
>
> -  dump_insns (uiout, di, low, high, how_many, flags, NULL);
> +  dump_insns (gdbarch, uiout, low, high, how_many, flags, NULL);
>
>    do_cleanups (ui_out_chain);
>  }
> @@ -818,9 +812,6 @@ gdb_disassembly (struct gdbarch *gdbarch, struct ui_out *uiout,
>  		 char *file_string, int flags, int how_many,
>  		 CORE_ADDR low, CORE_ADDR high)
>  {
> -  struct ui_file *stb = mem_fileopen ();
> -  struct cleanup *cleanups = make_cleanup_ui_file_delete (stb);
> -  gdb_disassembler di (gdbarch, stb);
>    struct symtab *symtab;
>    int nlines = -1;
>
> @@ -832,17 +823,16 @@ gdb_disassembly (struct gdbarch *gdbarch, struct ui_out *uiout,
>
>    if (!(flags & (DISASSEMBLY_SOURCE_DEPRECATED | DISASSEMBLY_SOURCE))
>        || nlines <= 0)
> -    do_assembly_only (uiout, &di, low, high, how_many, flags);
> +    do_assembly_only (gdbarch, uiout, low, high, how_many, flags);
>
>    else if (flags & DISASSEMBLY_SOURCE)
> -    do_mixed_source_and_assembly (gdbarch, uiout, &di, symtab, low, high,
> +    do_mixed_source_and_assembly (gdbarch, uiout, symtab, low, high,
>  				  how_many, flags);
>
>    else if (flags & DISASSEMBLY_SOURCE_DEPRECATED)
> -    do_mixed_source_and_assembly_deprecated (uiout, &di, symtab,
> +    do_mixed_source_and_assembly_deprecated (gdbarch, uiout, symtab,
>  					     low, high, how_many, flags);
>
> -  do_cleanups (cleanups);
>    gdb_flush (gdb_stdout);
>  }
>
> diff --git a/gdb/disasm.h b/gdb/disasm.h
> index 7bbfa31..dffe9cd 100644
> --- a/gdb/disasm.h
> +++ b/gdb/disasm.h
> @@ -44,11 +44,6 @@ public:
>
>    int print_insn (CORE_ADDR memaddr, int *branch_delay_insns = NULL);
>
> -  /* Prints the instruction INSN into UIOUT and returns the length of
> -     the printed instruction in bytes.  */
> -  int pretty_print_insn (struct ui_out *uiout,
> -			 const struct disasm_insn *insn, int flags);
> -
>    /* Return the gdbarch of gdb_disassembler.  */
>    struct gdbarch *arch ()
>    { return m_gdbarch; }
> @@ -102,6 +97,12 @@ extern void gdb_disassembly (struct gdbarch *gdbarch, struct ui_out *uiout,
>  extern int gdb_print_insn (struct gdbarch *gdbarch, CORE_ADDR memaddr,
>  			   struct ui_file *stream, int *branch_delay_insns);
>
> +/* Prints the instruction INSN into UIOUT and returns the length of
> +   the printed instruction in bytes.  */
> +
> +extern int gdb_pretty_print_insn (struct gdbarch *gdbarch, struct ui_out *uiout,
> +				  const struct disasm_insn *insn, int flags);
> +
>  /* Return the length in bytes of the instruction at address MEMADDR in
>     debugged memory.  */
>
> diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
> index 8896241..80b8aff 100644
> --- a/gdb/record-btrace.c
> +++ b/gdb/record-btrace.c
> @@ -696,7 +696,6 @@ btrace_insn_history (struct ui_out *uiout,
>  		     const struct btrace_insn_iterator *begin,
>  		     const struct btrace_insn_iterator *end, int flags)
>  {
> -  struct ui_file *stb;
>    struct cleanup *cleanups, *ui_item_chain;
>    struct gdbarch *gdbarch;
>    struct btrace_insn_iterator it;
> @@ -708,12 +707,9 @@ btrace_insn_history (struct ui_out *uiout,
>    flags |= DISASSEMBLY_SPECULATIVE;
>
>    gdbarch = target_gdbarch ();
> -  stb = mem_fileopen ();
> -  cleanups = make_cleanup_ui_file_delete (stb);
> -  gdb_disassembler di (gdbarch, stb);
>    last_lines = btrace_mk_line_range (NULL, 0, 0);
>
> -  make_cleanup_ui_out_list_begin_end (uiout, "asm_insns");
> +  cleanups = make_cleanup_ui_out_list_begin_end (uiout, "asm_insns");
>
>    /* UI_ITEM_CHAIN is a cleanup chain for the last source line and the
>       instructions corresponding to that line.  */
> @@ -772,7 +768,7 @@ btrace_insn_history (struct ui_out *uiout,
>  	  if ((insn->flags & BTRACE_INSN_FLAG_SPECULATIVE) != 0)
>  	    dinsn.is_speculative = 1;
>
> -	  di.pretty_print_insn (uiout, &dinsn, flags);
> +	  gdb_pretty_print_insn (gdbarch, uiout, &dinsn, flags);
>  	}
>      }
>
>

This looks fine to me.