Re: Regression with -D_GLIBCXX_DEBUG [Re: [PATCH 1/5] Make delim_string_to_char_ptr_vec return an std::vector]

[Simon Marchi <simon dot marchi at ericsson dot com>]

On 2018-04-10 03:58 PM, Jan Kratochvil wrote:
> Hi,
> 
> commit e80aaf6183c6692ecc167bf26cbdc53f8f1a55f0 (HEAD)
> Author: Simon Marchi <simon.marchi@polymtl.ca>
> Date:   Fri Mar 2 23:22:06 2018 -0500
>     Make delim_string_to_char_ptr_vec return an std::vector
> 
> /usr/include/c++/7/debug/safe_iterator.h:297:
> Error: attempt to increment a singular iterator.
> Objects involved in the operation:
>     iterator "this" @ 0x0x7fffffffd140 {
>       type = __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<std::unique_ptr<char, gdb::xfree_deleter<char> >*, std::__cxx1998::vector<std::unique_ptr<char, gdb::xfree_deleter<char> >, std::allocator<std::unique_ptr<char, gdb::xfree_deleter<char> > > > >, std::__debug::vector<std::unique_ptr<char, gdb::xfree_deleter<char> >, std::allocator<std::unique_ptr<char, gdb::xfree_deleter<char> > > > > (mutable iterator);
>       state = singular;
>       references sequence with type 'std::__debug::vector<std::unique_ptr<char, gdb::xfree_deleter<char> >, std::allocator<std::unique_ptr<char, gdb::xfree_deleter<char> > > >' @ 0x0x265db40
>     }
> #4  0x000000000078f893 in auto_load_safe_path_vec_update () at auto-load.c:212
> 
> 
> On Sun, 25 Feb 2018 17:32:43 +0100, Simon Marchi wrote:
>>    /* Apply tilde_expand and gdb_realpath to each AUTO_LOAD_SAFE_PATH_VEC
>>       element.  */
>> -  for (ix = 0; ix < len; ix++)
>> +  for (gdb::unique_xmalloc_ptr<char> &in_vec : auto_load_safe_path_vec)
>>      {
> ...
>> -	  VEC_safe_push (char_ptr, auto_load_safe_path_vec,
>> -			 real_path.release ());
>> +	  auto_load_safe_path_vec.push_back (std::move (real_path));
>>  	}
>>      }
>>  }
> 
> The iterator breaks when moving its std::vector data underneath it.
> This is why the original C code did not use a pointer there.
> 
> 
> Jan
> 

Of course, thanks for reporting.  Does this fix it?

>From fddee555819b2631920bf4a86854bb0d76ac121f Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@ericsson.com>
Date: Tue, 10 Apr 2018 16:31:52 -0400
Subject: [PATCH] Iterate by index

---
 gdb/auto-load.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/gdb/auto-load.c b/gdb/auto-load.c
index e426468..33d282a 100644
--- a/gdb/auto-load.c
+++ b/gdb/auto-load.c
@@ -197,20 +197,19 @@ auto_load_expand_dir_vars (const char *string)
 static void
 auto_load_safe_path_vec_update (void)
 {
-  unsigned len;
-  int ix;
-
   if (debug_auto_load)
     fprintf_unfiltered (gdb_stdlog,
 			_("auto-load: Updating directories of \"%s\".\n"),
 			auto_load_safe_path);

   auto_load_safe_path_vec = auto_load_expand_dir_vars (auto_load_safe_path);
+  size_t len = auto_load_safe_path_vec.size ();

   /* Apply tilde_expand and gdb_realpath to each AUTO_LOAD_SAFE_PATH_VEC
      element.  */
-  for (gdb::unique_xmalloc_ptr<char> &in_vec : auto_load_safe_path_vec)
+  for (size_t i = 0; i < len; i++)
     {
+      gdb::unique_xmalloc_ptr<char> &in_vec = auto_load_safe_path_vec[i];
       gdb::unique_xmalloc_ptr<char> expanded (tilde_expand (in_vec.get ()));
       gdb::unique_xmalloc_ptr<char> real_path = gdb_realpath (expanded.get ());

-- 
2.7.4