Patchwork [review] gdb: fix segfault in overload resolution debug output

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Submitter Simon Marchi (Code Review)
Date Nov. 29, 2019, 10:25 a.m.
Message ID <gerrit.1575023121000.Ia623f9637e82ec332bfeac23eb6b0f2ffdcdde27@gnutoolchain-gerrit.osci.io>
Download mbox | patch
Permalink /patch/36373/
State New
Headers show

Comments

Simon Marchi (Code Review) - Nov. 29, 2019, 10:25 a.m.
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/734
......................................................................

gdb: fix segfault in overload resolution debug output

A segfault occurs if overload resolution debug mode is turned on via
the 'set debug overload' command.  E.g.:

~~~
$ gdb ./a.out
...
(gdb) start
...
(gdb) set debug overload 1
(gdb) print foo(5)
-- Arg is int [8], parm is double [9]
Overloaded function instance (null) # of parms 1
Segmentation fault
$
~~~

The problem is, GDB tries to print the badness vector after it has
been std::move'd.  Fix the problem by printing the vector before it is
moved.

gdb/ChangeLog:
2019-11-29  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* valops.c (find_oload_champ): Print part of debug messages
	before the badness vector is std::move'd.

Change-Id: Ia623f9637e82ec332bfeac23eb6b0f2ffdcdde27
---
M gdb/valops.c
1 file changed, 25 insertions(+), 23 deletions(-)
Simon Marchi (Code Review) - Nov. 29, 2019, 11:06 a.m.
Andrew Burgess has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/734
......................................................................


Patch Set 1: Code-Review+2

LGTM.

Patch

diff --git a/gdb/valops.c b/gdb/valops.c
index cbb1f30..8af53de 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -3023,6 +3023,28 @@ 
       bv = rank_function (parm_types,
 			  args.slice (static_offset));
 
+      if (overload_debug)
+	{
+	  if (methods != NULL)
+	    fprintf_filtered (gdb_stderr,
+			      "Overloaded method instance %s, # of parms %d\n",
+			      methods[ix].physname, (int) parm_types.size ());
+	  else if (xmethods != NULL)
+	    fprintf_filtered (gdb_stderr,
+			      "Xmethod worker, # of parms %d\n",
+			      (int) parm_types.size ());
+	  else
+	    fprintf_filtered (gdb_stderr,
+			      "Overloaded function instance "
+			      "%s # of parms %d\n",
+			      functions[ix]->demangled_name (),
+			      (int) parm_types.size ());
+	  for (jj = 0; jj < args.size () - static_offset; jj++)
+	    fprintf_filtered (gdb_stderr,
+			      "...Badness @ %d : %d\n",
+			      jj, bv[jj].rank);
+	}
+
       if (oload_champ_bv->empty ())
 	{
 	  *oload_champ_bv = std::move (bv);
@@ -3048,29 +3070,9 @@ 
 	    break;
 	  }
       if (overload_debug)
-	{
-	  if (methods != NULL)
-	    fprintf_filtered (gdb_stderr,
-			      "Overloaded method instance %s, # of parms %d\n",
-			      methods[ix].physname, (int) parm_types.size ());
-	  else if (xmethods != NULL)
-	    fprintf_filtered (gdb_stderr,
-			      "Xmethod worker, # of parms %d\n",
-			      (int) parm_types.size ());
-	  else
-	    fprintf_filtered (gdb_stderr,
-			      "Overloaded function instance "
-			      "%s # of parms %d\n",
-			      functions[ix]->demangled_name (),
-			      (int) parm_types.size ());
-	  for (jj = 0; jj < args.size () - static_offset; jj++)
-	    fprintf_filtered (gdb_stderr,
-			      "...Badness @ %d : %d\n", 
-			      jj, bv[jj].rank);
-	  fprintf_filtered (gdb_stderr, "Overload resolution "
-			    "champion is %d, ambiguous? %d\n", 
-			    oload_champ, oload_ambiguous);
-	}
+	fprintf_filtered (gdb_stderr, "Overload resolution "
+			  "champion is %d, ambiguous? %d\n",
+			  oload_champ, oload_ambiguous);
     }
 
   return oload_champ;