Re: [PING^3] Generalize 'gcc/input.h:struct location_hash' (was: [Committed] [PATCH 2/4] (v4) On-demand locations within string-literals)

[Thomas Schwinge <thomas@codesourcery.com>]

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Hi!

On 2021-10-17T16:33:03-0600, Jeff Law via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> On 9/30/2021 12:47 AM, Thomas Schwinge wrote:
>> On 2021-09-17T13:16:14+0200, I wrote:
>>> On 2021-09-10T09:48:56+0200, I wrote:
>>>> On 2021-09-03T18:33:37+0200, I wrote:
>>>>> On 2021-09-02T21:09:54+0200, I wrote:
>>>>>> On 2021-09-02T15:59:14+0200, I wrote:
>>>>>>> On 2016-08-05T14:16:58-0400, David Malcolm <dmalcolm@redhat.com> wrote:
>>>>>>>> Committed to trunk as r239175; I'm attaching the final version of the
>>>>>>>> patch for reference.
>>>>>>> David, you've added here 'gcc/input.h:struct location_hash' (see quoted
>>>>>>> below), which will be useful elsewhere, so:
>>>>>>>> --- a/gcc/input.h
>>>>>>>> +++ b/gcc/input.h
>>>>>>>> +struct location_hash : int_hash <location_t, UNKNOWN_LOCATION> { };
>>>>>>>> +
>>>>>>>> +class GTY(()) string_concat_db
>>>>>>>> +{
>>>>>>>> +[...]
>>>>>>>> +  hash_map <location_hash, string_concat *> *m_table;
>>>>>>>> +};
>>>>>>> OK to push the attached
>>>>>>> "Generalize 'gcc/input.h:struct location_hash'"?

> OK

Thanks.  With the commentary slightly updated for PR103157 "'gengtype':
'typedef' causing infinite-recursion code to be generated", I've pushed
to master branch commit 088199e5d0fc0d54f48af0783a2630a773bbb387
"Generalize 'gcc/input.h:struct location_hash'", see attached.


Grüße
 Thomas


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From 088199e5d0fc0d54f48af0783a2630a773bbb387 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Tue, 31 Aug 2021 23:30:25 +0200
Subject: [PATCH] Generalize 'gcc/input.h:struct location_hash'

This is currently only used here ('gcc/input.h:class string_concat_db'), but is
actually generally useful, so advertize it as such.

Per the rationale given, we may use 'BUILTINS_LOCATION' as spare value for
'Deleted', in addition to the existing use of 'UNKNOWN_LOCATION' as spare value
for 'Empty'.

	gcc/
	* input.h (location_hash): Use 'BUILTINS_LOCATION' as spare value
	for 'Deleted'.  Turn into a '#define'.
---
 gcc/input.h | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/gcc/input.h b/gcc/input.h
index f7b08bdc444..bc44ba2507f 100644
--- a/gcc/input.h
+++ b/gcc/input.h
@@ -36,6 +36,28 @@ extern GTY(()) class line_maps *saved_line_table;
    both UNKNOWN_LOCATION and BUILTINS_LOCATION fit into that.  */
 STATIC_ASSERT (BUILTINS_LOCATION < RESERVED_LOCATION_COUNT);
 
+/* Hasher for 'location_t' values satisfying '!RESERVED_LOCATION_P', thus able
+   to use 'UNKNOWN_LOCATION'/'BUILTINS_LOCATION' as spare values for
+   'Empty'/'Deleted'.  */
+/* Per PR103157 "'gengtype': 'typedef' causing infinite-recursion code to be
+   generated", don't use
+       typedef int_hash<location_t, UNKNOWN_LOCATION, BUILTINS_LOCATION>
+         location_hash;
+   here.
+
+   It works for a single-use case, but when using a 'struct'-based variant
+       struct location_hash
+         : int_hash<location_t, UNKNOWN_LOCATION, BUILTINS_LOCATION> {};
+   in more than one place, 'gengtype' generates duplicate functions (thus:
+   "error: redefinition of 'void gt_ggc_mx(location_hash&)'" etc.).
+   Attempting to mark that one up with GTY options, we run into a 'gengtype'
+   "parse error: expected '{', have '<'", which probably falls into category
+   "understanding of C++ is limited", as documented in 'gcc/doc/gty.texi'.
+
+   Thus, use a plain ol' '#define':
+*/
+#define location_hash int_hash<location_t, UNKNOWN_LOCATION, BUILTINS_LOCATION>
+
 extern bool is_location_from_builtin_token (location_t);
 extern expanded_location expand_location (location_t);
 
@@ -233,8 +255,6 @@ public:
   location_t * GTY ((atomic)) m_locs;
 };
 
-struct location_hash : int_hash <location_t, UNKNOWN_LOCATION> { };
-
 class GTY(()) string_concat_db
 {
  public:
-- 
2.33.0