Re: [PATCH 1/2] Avoid manual memory management in go-lang.c

[Andrew Burgess <aburgess@redhat.com>]

Tom Tromey <tom@tromey.com> writes:

> I noticed a couple of spots in go-lang.c that could be improved by
> using unique_ptr.
> ---
>  gdb/dwarf2/read.c |  2 +-
>  gdb/go-exp.y      |  8 ++++----
>  gdb/go-lang.c     | 40 ++++++++++++++++++----------------------
>  gdb/go-lang.h     | 11 ++++++++---
>  4 files changed, 31 insertions(+), 30 deletions(-)
>
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index eb37c776989..4fd46fd43f8 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -5838,7 +5838,7 @@ fixup_go_packaging (struct dwarf2_cu *cu)
>  	      && sym->aclass () == LOC_BLOCK)
>  	    {
>  	      gdb::unique_xmalloc_ptr<char> this_package_name
> -		(go_symbol_package_name (sym));
> +		= go_symbol_package_name (sym);
>  
>  	      if (this_package_name == NULL)
>  		continue;
> diff --git a/gdb/go-exp.y b/gdb/go-exp.y
> index 242e7103b94..6aa4c426df6 100644
> --- a/gdb/go-exp.y
> +++ b/gdb/go-exp.y
> @@ -1396,16 +1396,16 @@ classify_name (struct parser_state *par_state, const struct block *block)
>       current package.  */
>  
>    {
> -    char *current_package_name = go_block_package_name (block);
> +    gdb::unique_xmalloc_ptr<char> current_package_name
> +      = go_block_package_name (block);
>  
>      if (current_package_name != NULL)
>        {
>  	struct stoken sval =
> -	  build_packaged_name (current_package_name,
> -			       strlen (current_package_name),
> +	  build_packaged_name (current_package_name.get (),
> +			       strlen (current_package_name.get ()),
>  			       copy.c_str (), copy.size ());
>  
> -	xfree (current_package_name);
>  	sym = lookup_symbol (sval.ptr, block, VAR_DOMAIN,
>  			     &is_a_field_of_this);
>  	if (sym.symbol)
> diff --git a/gdb/go-lang.c b/gdb/go-lang.c
> index 7549f14dc63..f9176ace71d 100644
> --- a/gdb/go-lang.c
> +++ b/gdb/go-lang.c
> @@ -163,11 +163,8 @@ unpack_package_and_object (char *buf,
>  
>     Space for the resulting strings is malloc'd in one buffer.
>     PACKAGEP,OBJECTP,METHOD_TYPE* will (typically) point into this buffer.
> -   [There are a few exceptions, but the caller is still responsible for
> -   freeing the resulting pointer.]
>     A pointer to this buffer is returned, or NULL if symbol isn't a
>     mangled Go symbol.
> -   The caller is responsible for freeing the result.
>  
>     *METHOD_TYPE_IS_POINTERP is set to a boolean indicating if
>     the method type is a pointer.
> @@ -180,7 +177,7 @@ unpack_package_and_object (char *buf,
>     If we ever need to unpack the method type, this routine should work
>     for that too.  */
>  
> -static char *
> +static gdb::unique_xmalloc_ptr<char>
>  unpack_mangled_go_symbol (const char *mangled_name,
>  			  const char **packagep,
>  			  const char **objectp,
> @@ -209,9 +206,10 @@ unpack_mangled_go_symbol (const char *mangled_name,
>    /* main.init is mangled specially.  */
>    if (strcmp (mangled_name, "__go_init_main") == 0)
>      {
> -      char *package = xstrdup ("main");
> +      gdb::unique_xmalloc_ptr<char> package
> +	= make_unique_xstrdup ("main");
>  
> -      *packagep = package;
> +      *packagep = package.get ();
>        *objectp = "init";
>        return package;
>      }
> @@ -219,9 +217,10 @@ unpack_mangled_go_symbol (const char *mangled_name,
>    /* main.main is mangled specially (missing prefix).  */
>    if (strcmp (mangled_name, "main.main") == 0)
>      {
> -      char *package = xstrdup ("main");
> +      gdb::unique_xmalloc_ptr<char> package
> +	= make_unique_xstrdup ("main");
>  
> -      *packagep = package;
> +      *packagep = package.get ();
>        *objectp = "main";
>        return package;
>      }
> @@ -261,7 +260,8 @@ unpack_mangled_go_symbol (const char *mangled_name,
>  
>    /* At this point we've decided we have a mangled Go symbol.  */
>  
> -  buf = xstrdup (mangled_name);
> +  gdb::unique_xmalloc_ptr<char> result = make_unique_xstrdup (mangled_name);
> +  buf = result.get ();
>  
>    /* Search backwards looking for "N<digit(s)>".  */
>    p = buf + len;
> @@ -317,7 +317,7 @@ unpack_mangled_go_symbol (const char *mangled_name,
>      }
>  
>    unpack_package_and_object (buf, packagep, objectp);
> -  return buf;
> +  return result;
>  }
>  
>  /* Implements the la_demangle language_defn routine for language Go.
> @@ -381,10 +381,9 @@ go_language::demangle_symbol (const char *mangled_name, int options) const
>    return make_unique_xstrdup ((const char *) obstack_finish (&tempbuf));
>  }
>  
> -/* Given a Go symbol, return its package or NULL if unknown.
> -   Space for the result is malloc'd, caller must free.  */
> +/* See go-lang.h.  */
>  
> -char *
> +gdb::unique_xmalloc_ptr<char>
>  go_symbol_package_name (const struct symbol *sym)
>  {
>    const char *mangled_name = sym->linkage_name ();
> @@ -393,8 +392,7 @@ go_symbol_package_name (const struct symbol *sym)
>    const char *method_type_package_name;
>    const char *method_type_object_name;
>    int method_type_is_pointer;
> -  char *name_buf;
> -  char *result;
> +  gdb::unique_xmalloc_ptr<char> name_buf;
>  
>    gdb_assert (sym->language () == language_go);
>    name_buf = unpack_mangled_go_symbol (mangled_name,
> @@ -405,15 +403,12 @@ go_symbol_package_name (const struct symbol *sym)
>    /* Some Go symbols don't have mangled form we interpret (yet).  */
>    if (name_buf == NULL)
>      return NULL;
> -  result = xstrdup (package_name);
> -  xfree (name_buf);
> -  return result;
> +  return make_unique_xstrdup (package_name);
>  }
>  
> -/* Return the package that BLOCK is in, or NULL if there isn't one.
> -   Space for the result is malloc'd, caller must free.  */
> +/* See go-lang.h.  */
>  
> -char *
> +gdb::unique_xmalloc_ptr<char>
>  go_block_package_name (const struct block *block)
>  {
>    while (block != NULL)
> @@ -422,7 +417,8 @@ go_block_package_name (const struct block *block)
>  
>        if (function != NULL)
>  	{
> -	  char *package_name = go_symbol_package_name (function);
> +	  gdb::unique_xmalloc_ptr<char> package_name
> +	    = go_symbol_package_name (function);
>  
>  	  if (package_name != NULL)
>  	    return package_name;
> diff --git a/gdb/go-lang.h b/gdb/go-lang.h
> index 1820b4c9658..877b6175534 100644
> --- a/gdb/go-lang.h
> +++ b/gdb/go-lang.h
> @@ -63,9 +63,14 @@ extern const char *go_main_name (void);
>  
>  extern enum go_type go_classify_struct_type (struct type *type);
>  
> -extern char *go_symbol_package_name (const struct symbol *sym);
> -
> -extern char *go_block_package_name (const struct block *block);
> +/* Given a Go symbol, return its package or NULL if unknown.  */
> +extern gdb::unique_xmalloc_ptr<char> go_symbol_package_name
> +     (const struct symbol *sym);
> +
> +/* Return the package that BLOCK is in, or NULL if there isn't
> +   one.  */
> +extern gdb::unique_xmalloc_ptr<char> go_block_package_name
> +     (const struct block *block);

Maybe replace NULL with nullptr in these comment.  But otherwise, this
all looks great.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>  
>  extern const struct builtin_go_type *builtin_go_type (struct gdbarch *);
>  
>
> -- 
> 2.39.1