Use std::sort instead of qsort in minsyms.c

  This has better typesafety and is also marginally faster (either
due to inlining or because it avoids indirection through a
function pointer).

Note that in this change:
-       return 1;               /* fn1 has no name, so it is "less".  */
+       return true;            /* fn1 has no name, so it is "less".  */
       else if (name1)          /* fn2 has no name, so it is "less".  */
-       return -1;
+       return false;
I am fairly sure the old code was wrong (ie. code didn't match the
comment and the comment seemed correct), so I fixed it.

gdb/ChangeLog:

2019-09-28  Christian Biesinger  <cbiesinger@google.com>

	* minsyms.c (compare_minimal_symbols): Rename to...
	(minimal_symbol_is_less_than): ...this, and adjust to STL
	conventions (return bool, take arguments as references)
	(minimal_symbol_reader::install): Call std::sort instead
	of qsort.
---
 gdb/minsyms.c | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)
  

* Christian Biesinger via gdb-patches <gdb-patches@sourceware.org> [2019-09-28 19:50:05 -0500]:

> This has better typesafety and is also marginally faster (either
> due to inlining or because it avoids indirection through a
> function pointer).
> 
> Note that in this change:
> -       return 1;               /* fn1 has no name, so it is "less".  */
> +       return true;            /* fn1 has no name, so it is "less".  */
>        else if (name1)          /* fn2 has no name, so it is "less".  */
> -       return -1;
> +       return false;
> I am fairly sure the old code was wrong (ie. code didn't match the
> comment and the comment seemed correct), so I fixed it.
> 
> gdb/ChangeLog:
> 
> 2019-09-28  Christian Biesinger  <cbiesinger@google.com>
> 
> 	* minsyms.c (compare_minimal_symbols): Rename to...
> 	(minimal_symbol_is_less_than): ...this, and adjust to STL
> 	conventions (return bool, take arguments as references)
> 	(minimal_symbol_reader::install): Call std::sort instead
> 	of qsort.
> ---
>  gdb/minsyms.c | 33 +++++++++++++--------------------
>  1 file changed, 13 insertions(+), 20 deletions(-)
> 
> diff --git a/gdb/minsyms.c b/gdb/minsyms.c
> index f06de4d88e..6384e7d72a 100644
> --- a/gdb/minsyms.c
> +++ b/gdb/minsyms.c
> @@ -1128,37 +1128,31 @@ minimal_symbol_reader::record_full (const char *name, int name_len,
>     on unsigned comparisons, so that we sort into unsigned numeric order.
>     Within groups with the same address, sort by name.  */

This comment ^^^ should be updated as it still talks about returning a
signed result.

>  
> -static int
> -compare_minimal_symbols (const void *fn1p, const void *fn2p)
> +static inline bool
> +minimal_symbol_is_less_than (const minimal_symbol &fn1, const minimal_symbol &fn2)

This line is too long now.

With those issues fixed this looks good to me.

Thanks,
Andrew

>  {
> -  const struct minimal_symbol *fn1;
> -  const struct minimal_symbol *fn2;
> -
> -  fn1 = (const struct minimal_symbol *) fn1p;
> -  fn2 = (const struct minimal_symbol *) fn2p;
> -
> -  if (MSYMBOL_VALUE_RAW_ADDRESS (fn1) < MSYMBOL_VALUE_RAW_ADDRESS (fn2))
> +  if (MSYMBOL_VALUE_RAW_ADDRESS (&fn1) < MSYMBOL_VALUE_RAW_ADDRESS (&fn2))
>      {
> -      return (-1);		/* addr 1 is less than addr 2.  */
> +      return true;		/* addr 1 is less than addr 2.  */
>      }
> -  else if (MSYMBOL_VALUE_RAW_ADDRESS (fn1) > MSYMBOL_VALUE_RAW_ADDRESS (fn2))
> +  else if (MSYMBOL_VALUE_RAW_ADDRESS (&fn1) > MSYMBOL_VALUE_RAW_ADDRESS (&fn2))
>      {
> -      return (1);		/* addr 1 is greater than addr 2.  */
> +      return false;		/* addr 1 is greater than addr 2.  */
>      }
>    else
>      /* addrs are equal: sort by name */
>      {
> -      const char *name1 = MSYMBOL_LINKAGE_NAME (fn1);
> -      const char *name2 = MSYMBOL_LINKAGE_NAME (fn2);
> +      const char *name1 = MSYMBOL_LINKAGE_NAME (&fn1);
> +      const char *name2 = MSYMBOL_LINKAGE_NAME (&fn2);
>  
>        if (name1 && name2)	/* both have names */
> -	return strcmp (name1, name2);
> +	return strcmp (name1, name2) < 0;
>        else if (name2)
> -	return 1;		/* fn1 has no name, so it is "less".  */
> +	return true;		/* fn1 has no name, so it is "less".  */
>        else if (name1)		/* fn2 has no name, so it is "less".  */
> -	return -1;
> +	return false;
>        else
> -	return (0);		/* Neither has a name, so they're equal.  */
> +	return false;		/* Neither has a name, so they're equal.  */
>      }
>  }
>  
> @@ -1315,8 +1309,7 @@ minimal_symbol_reader::install ()
>  
>        /* Sort the minimal symbols by address.  */
>  
> -      qsort (msymbols, mcount, sizeof (struct minimal_symbol),
> -	     compare_minimal_symbols);
> +      std::sort (msymbols, msymbols + mcount, minimal_symbol_is_less_than);
>  
>        /* Compact out any duplicates, and free up whatever space we are
>           no longer using.  */
> -- 
> 2.23.0.444.g18eeb5a265-goog
>
  

>>>>> "Christian" == Christian Biesinger via gdb-patches <gdb-patches@sourceware.org> writes:

Christian> Note that in this change:
Christian> -       return 1;               /* fn1 has no name, so it is "less".  */
Christian> +       return true;            /* fn1 has no name, so it is "less".  */
Christian>        else if (name1)          /* fn2 has no name, so it is "less".  */
Christian> -       return -1;
Christian> +       return false;
Christian> I am fairly sure the old code was wrong (ie. code didn't match the
Christian> comment and the comment seemed correct), so I fixed it.

Yeah, it looks like the values were switched -- i.e., returning 1 if
name1 was NULL, where it should have returned -1 in that case.  I think
this didn't matter in practice, though, because the sorting of this case
is arbitrary, so either way is fine as long as it is consistent.

Christian> 2019-09-28  Christian Biesinger  <cbiesinger@google.com>

Christian> 	* minsyms.c (compare_minimal_symbols): Rename to...
Christian> 	(minimal_symbol_is_less_than): ...this, and adjust to STL
Christian> 	conventions (return bool, take arguments as references)
Christian> 	(minimal_symbol_reader::install): Call std::sort instead
Christian> 	of qsort.

This is ok.  Thanks.

Tom
  

On Mon, Sep 30, 2019 at 8:36 AM Andrew Burgess
<andrew.burgess@embecosm.com> wrote:
>
> * Christian Biesinger via gdb-patches <gdb-patches@sourceware.org> [2019-09-28 19:50:05 -0500]:
>
> > This has better typesafety and is also marginally faster (either
> > due to inlining or because it avoids indirection through a
> > function pointer).
> >
> > Note that in this change:
> > -       return 1;               /* fn1 has no name, so it is "less".  */
> > +       return true;            /* fn1 has no name, so it is "less".  */
> >        else if (name1)          /* fn2 has no name, so it is "less".  */
> > -       return -1;
> > +       return false;
> > I am fairly sure the old code was wrong (ie. code didn't match the
> > comment and the comment seemed correct), so I fixed it.
> >
> > gdb/ChangeLog:
> >
> > 2019-09-28  Christian Biesinger  <cbiesinger@google.com>
> >
> >       * minsyms.c (compare_minimal_symbols): Rename to...
> >       (minimal_symbol_is_less_than): ...this, and adjust to STL
> >       conventions (return bool, take arguments as references)
> >       (minimal_symbol_reader::install): Call std::sort instead
> >       of qsort.
> > ---
> >  gdb/minsyms.c | 33 +++++++++++++--------------------
> >  1 file changed, 13 insertions(+), 20 deletions(-)
> >
> > diff --git a/gdb/minsyms.c b/gdb/minsyms.c
> > index f06de4d88e..6384e7d72a 100644
> > --- a/gdb/minsyms.c
> > +++ b/gdb/minsyms.c
> > @@ -1128,37 +1128,31 @@ minimal_symbol_reader::record_full (const char *name, int name_len,
> >     on unsigned comparisons, so that we sort into unsigned numeric order.
> >     Within groups with the same address, sort by name.  */
>
> This comment ^^^ should be updated as it still talks about returning a
> signed result.

Thanks, fixed.

> > -static int
> > -compare_minimal_symbols (const void *fn1p, const void *fn2p)
> > +static inline bool
> > +minimal_symbol_is_less_than (const minimal_symbol &fn1, const minimal_symbol &fn2)
>
> This line is too long now.
>
> With those issues fixed this looks good to me.

Fixed.

Pushed to master:
To ssh://sourceware.org/git/binutils-gdb.git
   4a56a52007..6fb08628e0  HEAD -> master

Christian

> > -  const struct minimal_symbol *fn1;
> > -  const struct minimal_symbol *fn2;
> > -
> > -  fn1 = (const struct minimal_symbol *) fn1p;
> > -  fn2 = (const struct minimal_symbol *) fn2p;
> > -
> > -  if (MSYMBOL_VALUE_RAW_ADDRESS (fn1) < MSYMBOL_VALUE_RAW_ADDRESS (fn2))
> > +  if (MSYMBOL_VALUE_RAW_ADDRESS (&fn1) < MSYMBOL_VALUE_RAW_ADDRESS (&fn2))
> >      {
> > -      return (-1);           /* addr 1 is less than addr 2.  */
> > +      return true;           /* addr 1 is less than addr 2.  */
> >      }
> > -  else if (MSYMBOL_VALUE_RAW_ADDRESS (fn1) > MSYMBOL_VALUE_RAW_ADDRESS (fn2))
> > +  else if (MSYMBOL_VALUE_RAW_ADDRESS (&fn1) > MSYMBOL_VALUE_RAW_ADDRESS (&fn2))
> >      {
> > -      return (1);            /* addr 1 is greater than addr 2.  */
> > +      return false;          /* addr 1 is greater than addr 2.  */
> >      }
> >    else
> >      /* addrs are equal: sort by name */
> >      {
> > -      const char *name1 = MSYMBOL_LINKAGE_NAME (fn1);
> > -      const char *name2 = MSYMBOL_LINKAGE_NAME (fn2);
> > +      const char *name1 = MSYMBOL_LINKAGE_NAME (&fn1);
> > +      const char *name2 = MSYMBOL_LINKAGE_NAME (&fn2);
> >
> >        if (name1 && name2)    /* both have names */
> > -     return strcmp (name1, name2);
> > +     return strcmp (name1, name2) < 0;
> >        else if (name2)
> > -     return 1;               /* fn1 has no name, so it is "less".  */
> > +     return true;            /* fn1 has no name, so it is "less".  */
> >        else if (name1)                /* fn2 has no name, so it is "less".  */
> > -     return -1;
> > +     return false;
> >        else
> > -     return (0);             /* Neither has a name, so they're equal.  */
> > +     return false;           /* Neither has a name, so they're equal.  */
> >      }
> >  }
> >
> > @@ -1315,8 +1309,7 @@ minimal_symbol_reader::install ()
> >
> >        /* Sort the minimal symbols by address.  */
> >
> > -      qsort (msymbols, mcount, sizeof (struct minimal_symbol),
> > -          compare_minimal_symbols);
> > +      std::sort (msymbols, msymbols + mcount, minimal_symbol_is_less_than);
> >
> >        /* Compact out any duplicates, and free up whatever space we are
> >           no longer using.  */
> > --
> > 2.23.0.444.g18eeb5a265-goog
> >