[PING^2] Re: [Committed] [PATCH 2/4] (v4) On-demand locations within string-literals

[Thomas Schwinge <thomas@codesourcery.com>]

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Hi!

On 2021-09-10T09:48:56+0200, I wrote:
> Ping.  My patches again attached, for easy reference.

Ping once again.


Grüße
 Thomas


> On 2021-09-03T18:33:37+0200, I wrote:
>> Hi!
>>
>> 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.c
>>>>> +++ b/gcc/input.c
>>>>
>>>>> +/* Internal function.  Canonicalize LOC into a form suitable for
>>>>> +   use as a key within the database, stripping away macro expansion,
>>>>> +   ad-hoc information, and range information, using the location of
>>>>> +   the start of LOC within an ordinary linemap.  */
>>>>> +
>>>>> +location_t
>>>>> +string_concat_db::get_key_loc (location_t loc)
>>>>> +{
>>>>> +  loc = linemap_resolve_location (line_table, loc, LRK_SPELLING_LOCATION,
>>>>> +                             NULL);
>>>>> +
>>>>> +  loc = get_range_from_loc (line_table, loc).m_start;
>>>>> +
>>>>> +  return loc;
>>>>> +}
>>>>
>>>> OK to push the attached
>>>> "Harden 'gcc/input.c:string_concat_db::get_key_loc'"?  (This fell out of
>>>> my analysis for development work elsewhere.)
>>>
>>> My suggested patch was:
>>>
>>>     --- a/gcc/input.c
>>>     +++ b/gcc/input.c
>>>     @@ -1483,6 +1483,9 @@ string_concat_db::get_key_loc (location_t loc)
>>>
>>>        loc = get_range_from_loc (line_table, loc).m_start;
>>>
>>>     +  /* Ascertain that 'loc' is valid as a key in 'm_table'.  */
>>>     +  gcc_checking_assert (!RESERVED_LOCATION_P (loc));
>>>     +
>>>        return loc;
>>>      }
>>>
>>> Uh, I should've looked at the correct test logs...  This change actually
>>> does regress 'c-c++-common/substring-location-PR-87721.c' and
>>> 'gcc.dg/plugin/diagnostic-test-string-literals-1.c': for these, we do see
>>> 'BUILTINS_LOCATION' (via 'string_concat_db::record_string_concatenation').
>>> Unless someone tell me that's unexpected (I'm completely lost in this
>>> code...)
>>
>> I think I convinced myself that the current code doesn't have stable
>> behavior, so...
>>
>>> I shall change/generalize my changes to provide both a
>>> 'location_hash' only using 'UNKNOWN_LOCATION' as a spare value for
>>> 'Empty' (as currently used here) and another variant additionally using
>>> 'BUILTINS_LOCATION' as spare value for 'Deleted'.
>>
>> ... I didn't do this, but instead would like to push the attached
>> "Don't record string concatenation data for 'RESERVED_LOCATION_P'"
>> (replacing "Harden 'gcc/input.c:string_concat_db::get_key_loc'" as
>> originally proposed).  OK?
>>
>>
>> ... and then re:
>>
>>>>> --- 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'"?
>>
>> Attached again.
>>
>>
>> Grüße
>>  Thomas


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From 9f1066fcb770397d6e791aa0594f067a755e2ed6 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Fri, 3 Sep 2021 18:25:10 +0200
Subject: [PATCH] Don't record string concatenation data for
 'RESERVED_LOCATION_P'

'RESERVED_LOCATION_P' means 'UNKNOWN_LOCATION' or 'BUILTINS_LOCATION.
We're using 'UNKNOWN_LOCATION' as a spare value for 'Empty', so should
ascertain that we don't use it as a key additionally.  Similarly for
'BUILTINS_LOCATION' that we'd later like to use as a spare value for
'Deleted'.

As discussed in the source code comment added, for these we didn't have
stable behavior anyway.

Follow-up to r239175 (commit 88fa5555a309e5d6c6171b957daaf2f800920869)
"On-demand locations within string-literals".

	gcc/
	* input.c (string_concat_db::record_string_concatenation)
	(string_concat_db::get_string_concatenation): Skip for
	'RESERVED_LOCATION_P'.
	gcc/testsuite/
	* gcc.dg/plugin/diagnostic-test-string-literals-1.c: Adjust
	expected error diagnostics.
---
 gcc/input.c                                              | 9 +++++++++
 .../gcc.dg/plugin/diagnostic-test-string-literals-1.c    | 4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/gcc/input.c b/gcc/input.c
index 4b809862e02..dd753decfa0 100644
--- a/gcc/input.c
+++ b/gcc/input.c
@@ -1437,6 +1437,11 @@ string_concat_db::record_string_concatenation (int num, location_t *locs)
   gcc_assert (locs);
 
   location_t key_loc = get_key_loc (locs[0]);
+  /* We don't record data for 'RESERVED_LOCATION_P (key_loc)' key values:
+     any data now recorded under key 'key_loc' would be overwritten by a
+     subsequent call with the same key 'key_loc'.  */
+  if (RESERVED_LOCATION_P (key_loc))
+    return;
 
   string_concat *concat
     = new (ggc_alloc <string_concat> ()) string_concat (num, locs);
@@ -1460,6 +1465,10 @@ string_concat_db::get_string_concatenation (location_t loc,
   gcc_assert (out_locs);
 
   location_t key_loc = get_key_loc (loc);
+  /* We don't record data for 'RESERVED_LOCATION_P (key_loc)' key values; see
+     discussion in 'string_concat_db::record_string_concatenation'.  */
+  if (RESERVED_LOCATION_P (key_loc))
+    return false;
 
   string_concat **concat = m_table->get (key_loc);
   if (!concat)
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
index 4cba87be2ae..8818192eb45 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
@@ -332,8 +332,8 @@ pr87652 (const char *stem, int counter)
 				OFFSET + end_idx);		\
   } while (0)
 
-/* { dg-error "unable to read substring location: unable to read source line" "" { target c } 329 } */
-/* { dg-error "unable to read substring location: failed to get ordinary maps" "" { target c++ } 329 } */
+/* { dg-error "unable to read substring location: failed to get ordinary maps" "" { target c } 329 } */
+/* { dg-error "unable to read substring location: macro expansion" "" { target c++ } 329 } */
 /* { dg-begin-multiline-output "" }
      __emit_string_literal_range(__FILE__":%5d: " format,        \
                                  ^~~~~~~~
-- 
2.25.1


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From 349a3172f64db93ee98ea39b36489b702b6596ab Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Tue, 31 Aug 2021 23:30:25 +0200
Subject: [PATCH 2/2] 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 | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/gcc/input.h b/gcc/input.h
index e6881072c5f..46971a2684c 100644
--- a/gcc/input.h
+++ b/gcc/input.h
@@ -36,6 +36,25 @@ 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'.  */
+/* If the following is used more than once, 'gengtype' generates duplicate
+   functions (thus: "error: redefinition of 'void gt_ggc_mx(location_hash&)'"
+   etc.):
+
+       struct location_hash
+         : int_hash<location_t, UNKNOWN_LOCATION, BUILTINS_LOCATION> {};
+
+   Likewise for this:
+
+       typedef int_hash<location_t, UNKNOWN_LOCATION, BUILTINS_LOCATION>
+         location_hash;
+
+   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);
 
@@ -230,8 +249,6 @@ 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