[RFC/7.10] Temp fix for 17960 assertion failure?

[Doug Evans]

Doug Evans writes:
  > On Fri, Aug 7, 2015 at 8:48 AM, Keith Seitz <keiths@redhat.com> wrote:
  > > Hi, Doug,
  > >
  > > A while ago you posted a temporary patch to squash the completer
  > > assertion failure reported in 17960:
  > >
  > > (gdb) break gdb.c:ma<TAB>
  > > ./../src/gdb/completer.c:837: internal-error: maybe_add_completion:
  > > Assertion `tracker != NULL' failed.
  > > A problem internal to GDB has been detected,
  > > further debugging may prove unreliable.
  > >
  > > Proposed patch:
  > > https://sourceware.org/ml/gdb-patches/2015-02/msg00830.html
  > >
  > > Should we add this to 7.10?
  >
  > Ah, righto.
  > Sounds good to me.
  > I'll take care of it.

[apologies if you get this twice, mailer problems]

Heya, thanks for flagging this.
It's great to not let this get into 7.10.

Here's the patch that I committed to trunk and 7.10.
I had to tweak the testcase to trigger the bug
as the .exp had changed a bit and max-completions
was now "unlimited" at the point of the test, whereas
the test requires a fixed limit.
I verified an unpatched gdb still crashes with the test.

2015-08-10  Doug Evans  <dje@google.com>
	    Keith Seitz  <keiths@redhat.com>

	PR gdb/17960
	* symtab.c (make_file_symbol_completion_list_1): Renamed from
	make_file_symbol_completion_list and made static.
	(make_file_symbol_completion_list): New function.
	
	testsuite/
	* gdb.base/completion.exp: Add location completer tests.

diff --git a/gdb/symtab.c b/gdb/symtab.c
index ebafe53..5278265 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -5604,9 +5604,9 @@ make_symbol_completion_list_fn (struct  
cmd_list_element *ignore,
  /* Like make_symbol_completion_list, but returns a list of symbols
     defined in a source file FILE.  */

-VEC (char_ptr) *
-make_file_symbol_completion_list (const char *text, const char *word,
-				  const char *srcfile)
+static VEC (char_ptr) *
+make_file_symbol_completion_list_1 (const char *text, const char *word,
+				    const char *srcfile)
  {
    struct symbol *sym;
    struct symtab *s;
@@ -5662,8 +5662,6 @@ make_file_symbol_completion_list (const char *text,  
const char *word,

    sym_text_len = strlen (sym_text);

-  return_val = NULL;
-
    /* Find the symtab for SRCFILE (this loads it if it was not yet read
       in).  */
    s = lookup_symtab (srcfile);
@@ -5699,6 +5697,36 @@ make_file_symbol_completion_list (const char *text,  
const char *word,
    return (return_val);
  }

+/* Wrapper around make_file_symbol_completion_list_1
+   to handle MAX_COMPLETIONS_REACHED_ERROR.  */
+
+VEC (char_ptr) *
+make_file_symbol_completion_list (const char *text, const char *word,
+				  const char *srcfile)
+{
+  struct cleanup *back_to, *cleanups;
+
+  completion_tracker = new_completion_tracker ();
+  cleanups = make_cleanup_free_completion_tracker (&completion_tracker);
+  return_val = NULL;
+  back_to = make_cleanup (do_free_completion_list, &return_val);
+
+  TRY
+    {
+      make_file_symbol_completion_list_1 (text, word, srcfile);
+    }
+  CATCH (except, RETURN_MASK_ERROR)
+    {
+      if (except.error != MAX_COMPLETIONS_REACHED_ERROR)
+	throw_exception (except);
+    }
+  END_CATCH
+
+  discard_cleanups (back_to);
+  do_cleanups (cleanups);
+  return return_val;
+}
+
  /* A helper function for make_source_files_completion_list.  It adds
     another file name to a list of possible completions, growing the
     list as necessary.  */
diff --git a/gdb/testsuite/gdb.base/completion.exp  
b/gdb/testsuite/gdb.base/completion.exp
index 1eb0fd8..f0e4dec 100644
--- a/gdb/testsuite/gdb.base/completion.exp
+++ b/gdb/testsuite/gdb.base/completion.exp
@@ -777,6 +777,88 @@ gdb_test_multiple "" "$test" {
  }

  #
+# Tests for the location completer
+#
+
+# Turn off pending breakpoint support so that we don't get queried
+# all the time.
+gdb_test_no_output "set breakpoint pending off"
+
+set subsrc [string range $srcfile 0 [expr {[string length $srcfile] - 3}]]
+set test "tab complete break $subsrc"
+send_gdb "break $subsrc\t\t"
+gdb_test_multiple "" $test {
+    -re "break\.c.*break1\.c.*$gdb_prompt " {
+	send_gdb "1\t\n"
+	gdb_test_multiple "" $test {
+	    -re ".*Function \"$srcfile2\" not defined\..*$gdb_prompt " {
+		pass $test
+	    }
+	    -re "$gdb_prompt p$" {
+		fail $test
+	    }
+	}
+    }
+
+    -re "$gdb_prompt p$" {
+	fail $test
+    }
+}
+
+gdb_test "complete break $subsrc" "break\.c.*break1\.c"
+
+set test "tab complete break need"
+send_gdb "break need\t"
+gdb_test_multiple "" $test {
+    -re "break need_malloc " {
+	send_gdb "\n"
+	gdb_test_multiple "" $test {
+	    -re ".*Breakpoint.*at .*/$srcfile, line .*$gdb_prompt " {
+		pass $test
+		gdb_test_no_output "delete breakpoint \$bpnum" \
+		    "delete breakpoint for $test"
+	    }
+	    -re "$gdb_prompt p$" {
+		fail $test
+	    }
+	}
+    }
+    -re "$gdb_prompt p$" {
+	fail $test
+    }
+}
+
+gdb_test "complete break need" "need_malloc"
+
+# gdb/17960
+# Enabling max-completions is necessary to trigger the bug.
+gdb_test_no_output "set max-completions 10"
+set test "tab complete break $srcfile:ma"
+send_gdb "break $srcfile:ma\t"
+gdb_test_multiple "" $test {
+    -re "break $srcfile:main " {
+	send_gdb "\n"
+	gdb_test_multiple "" $test {
+	    -re ".*Breakpoint.*at .*/$srcfile, line .*$gdb_prompt " {
+		pass $test
+		gdb_test_no_output "delete breakpoint \$bpnum" \
+		    "delete breakpoint for $test"
+	    }
+	    -re "$gdb_prompt p$" {
+		fail $test
+	    }
+	}
+    }
+    -re "$gdb_prompt p$" {
+	fail $test
+    }
+}
+
+gdb_test "complete break $srcfile:ma" "break\.c:main"
+
+# End of gdb/17960 testing.
+
+#
  # Completion limiting.
  #