Re: [PATCH] gdb: Remove a non-const reference parameter

[Sergio Durigan Junior <sergiodj at redhat dot com>]

On Tuesday, July 02 2019, Andrew Burgess wrote:

> Non-const reference parameter should be avoided according to the GDB
> coding standard:
>
>   https://sourceware.org/gdb/wiki/Internals%20GDB-C-Coding-Standards#Avoid_non-const_reference_parameters.2C_use_pointers_instead
>
> This commit updates the gdbarch method gdbarch_stap_adjust_register,
> and the one implementation i386_stap_adjust_register to avoid using a
> non-const reference parameter.
>
> I've also removed the kfail from the testsuite for bug 24541, as this
> issue is now resolved.

Thanks, Andrew (and sorry for the delay; yesterday was a holiday here).

This is OK.

> gdb/ChangeLog:
>
> 	PR breakpoints/24541
> 	* gdbarch.c: Regenerate.
> 	* gdbarch.h: Regenerate.
> 	* gdbarch.sh: Adjust return type and parameter types for
> 	'stap_adjust_register'.
> 	(i386_stap_adjust_register): Adjust signature and return new
> 	register name.
> 	* stap-probe.c (stap_parse_register_operand): Adjust use of
> 	'gdbarch_stap_adjust_register'.
>
> gdb/testsuite/ChangeLog:
>
> 	PR breakpoints/24541
> 	* gdb.mi/mi-catch-cpp-exceptions.exp: Remove kfail due to 24541.
> ---
>  gdb/ChangeLog                                    | 12 ++++++++++++
>  gdb/gdbarch.c                                    |  6 +++---
>  gdb/gdbarch.h                                    |  4 ++--
>  gdb/gdbarch.sh                                   |  2 +-
>  gdb/i386-tdep.c                                  | 12 ++++++++----
>  gdb/stap-probe.c                                 | 15 ++++++++-------
>  gdb/testsuite/ChangeLog                          |  5 +++++
>  gdb/testsuite/gdb.mi/mi-catch-cpp-exceptions.exp | 22 +---------------------
>  8 files changed, 40 insertions(+), 38 deletions(-)
>
> diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
> index cc7d0ace66c..725b98fcd9f 100644
> --- a/gdb/gdbarch.c
> +++ b/gdb/gdbarch.c
> @@ -4530,14 +4530,14 @@ gdbarch_stap_adjust_register_p (struct gdbarch *gdbarch)
>    return gdbarch->stap_adjust_register != NULL;
>  }
>  
> -void
> -gdbarch_stap_adjust_register (struct gdbarch *gdbarch, struct stap_parse_info *p, std::string &regname, int regnum)
> +std::string
> +gdbarch_stap_adjust_register (struct gdbarch *gdbarch, struct stap_parse_info *p, const std::string &regname, int regnum)
>  {
>    gdb_assert (gdbarch != NULL);
>    gdb_assert (gdbarch->stap_adjust_register != NULL);
>    if (gdbarch_debug >= 2)
>      fprintf_unfiltered (gdb_stdlog, "gdbarch_stap_adjust_register called\n");
> -  gdbarch->stap_adjust_register (gdbarch, p, regname, regnum);
> +  return gdbarch->stap_adjust_register (gdbarch, p, regname, regnum);
>  }
>  
>  void
> diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
> index 0857d2f3027..c3556d38419 100644
> --- a/gdb/gdbarch.h
> +++ b/gdb/gdbarch.h
> @@ -1376,8 +1376,8 @@ extern void set_gdbarch_stap_parse_special_token (struct gdbarch *gdbarch, gdbar
>  
>  extern int gdbarch_stap_adjust_register_p (struct gdbarch *gdbarch);
>  
> -typedef void (gdbarch_stap_adjust_register_ftype) (struct gdbarch *gdbarch, struct stap_parse_info *p, std::string &regname, int regnum);
> -extern void gdbarch_stap_adjust_register (struct gdbarch *gdbarch, struct stap_parse_info *p, std::string &regname, int regnum);
> +typedef std::string (gdbarch_stap_adjust_register_ftype) (struct gdbarch *gdbarch, struct stap_parse_info *p, const std::string &regname, int regnum);
> +extern std::string gdbarch_stap_adjust_register (struct gdbarch *gdbarch, struct stap_parse_info *p, const std::string &regname, int regnum);
>  extern void set_gdbarch_stap_adjust_register (struct gdbarch *gdbarch, gdbarch_stap_adjust_register_ftype *stap_adjust_register);
>  
>  /* DTrace related functions.
> diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh
> index f3d1bf489ac..2f9fbbc56cd 100755
> --- a/gdb/gdbarch.sh
> +++ b/gdb/gdbarch.sh
> @@ -1053,7 +1053,7 @@ M;int;stap_parse_special_token;struct stap_parse_info *p;p
>  # replace the register name from %ax to %eax.
>  #
>  # The rationale for this can be found at PR breakpoints/24541.
> -M;void;stap_adjust_register;struct stap_parse_info *p, std::string \&regname, int regnum;p, regname, regnum
> +M;std::string;stap_adjust_register;struct stap_parse_info *p, const std::string \&regname, int regnum;p, regname, regnum
>  
>  # DTrace related functions.
>  
> diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
> index 00c1f8d7499..b956604178f 100644
> --- a/gdb/i386-tdep.c
> +++ b/gdb/i386-tdep.c
> @@ -4389,9 +4389,9 @@ i386_stap_parse_special_token (struct gdbarch *gdbarch,
>  /* Implementation of 'gdbarch_stap_adjust_register', as defined in
>     gdbarch.h.  */
>  
> -static void
> +static std::string
>  i386_stap_adjust_register (struct gdbarch *gdbarch, struct stap_parse_info *p,
> -			   std::string &regname, int regnum)
> +			   const std::string &regname, int regnum)
>  {
>    static const std::unordered_set<std::string> reg_assoc
>      = { "ax", "bx", "cx", "dx",
> @@ -4402,14 +4402,18 @@ i386_stap_adjust_register (struct gdbarch *gdbarch, struct stap_parse_info *p,
>        /* If we're dealing with a register whose size is greater or
>  	 equal than the size specified by the "[-]N@" prefix, then we
>  	 don't need to do anything.  */
> -      return;
> +      return regname;
>      }
>  
>    if (reg_assoc.find (regname) != reg_assoc.end ())
>      {
>        /* Use the extended version of the register.  */
> -      regname = "e" + regname;
> +      std::string tmp = "e" + regname;
> +      return tmp;
>      }
> +
> +  /* Use the requested register.  */
> +  return regname;
>  }
>  
>  
> diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
> index aa1c8144d8a..747bbcfb8c1 100644
> --- a/gdb/stap-probe.c
> +++ b/gdb/stap-probe.c
> @@ -774,23 +774,24 @@ stap_parse_register_operand (struct stap_parse_info *p)
>       code would like to perform on the register name.  */
>    if (gdbarch_stap_adjust_register_p (gdbarch))
>      {
> -      std::string oldregname = regname;
> +      std::string newregname
> +	= gdbarch_stap_adjust_register (gdbarch, p, regname, regnum);
>  
> -      gdbarch_stap_adjust_register (gdbarch, p, regname, regnum);
> -
> -      if (regname != oldregname)
> +      if (regname != newregname)
>  	{
>  	  /* This is just a check we perform to make sure that the
>  	     arch-dependent code has provided us with a valid
>  	     register name.  */
> -	  regnum = user_reg_map_name_to_regnum (gdbarch, regname.c_str (),
> -						regname.size ());
> +	  regnum = user_reg_map_name_to_regnum (gdbarch, newregname.c_str (),
> +						newregname.size ());
>  
>  	  if (regnum == -1)
>  	    internal_error (__FILE__, __LINE__,
>  			    _("Invalid register name '%s' after replacing it"
>  			      " (previous name was '%s')"),
> -			    regname.c_str (), oldregname.c_str ());
> +			    newregname.c_str (), regname.c_str ());
> +
> +	  regname = newregname;
>  	}
>      }
>  
> diff --git a/gdb/testsuite/gdb.mi/mi-catch-cpp-exceptions.exp b/gdb/testsuite/gdb.mi/mi-catch-cpp-exceptions.exp
> index fa5b11e3e58..4b87e4b62ba 100644
> --- a/gdb/testsuite/gdb.mi/mi-catch-cpp-exceptions.exp
> +++ b/gdb/testsuite/gdb.mi/mi-catch-cpp-exceptions.exp
> @@ -130,27 +130,7 @@ with_test_prefix "all with invalid regexp" {
>      setup_catchpoint "throw" "-r blahblah"
>      setup_catchpoint "rethrow" "-r woofwoof"
>      setup_catchpoint "catch" "-r miowmiow"
> -
> -    # Would like to use 'continue_to_breakpoint_in_main' here, if
> -    # there wasn't a bug that requires a use of kfail.
> -
> -    mi_send_resuming_command "exec-continue" \
> -	"exec-continue"
> -    set testname "run until breakpoint in main"
> -    gdb_expect {
> -	-re "could not find minimal symbol for typeinfo address.*$mi_gdb_prompt$" {
> -	    kfail "gdb/24541" "${testname}"
> -	}
> -	-re "\\*stopped,bkptno=\"$decimal\",reason=\"breakpoint-hit\",disp=\"keep\".*func=\"__cxa_throw\".*$mi_gdb_prompt$" {
> -	    kfail "gdb/24541" "${testname}"
> -	}
> -	-re "\\*stopped,reason=\"breakpoint-hit\".*func=\"main\".*line=\"${main_lineno}\".*$mi_gdb_prompt$" {
> -	    pass "${testname}"
> -	}
> -	timeout {
> -	    fail "${testname} (timeout)"
> -	}
> -    }
> +    continue_to_breakpoint_in_main
>  }
>  
>  # Now check that all of the commands with a regexp that does match,
> -- 
> 2.14.5

-- 
Sergio
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