PR 18303, Tolerate malformed input for lookup_symbol-called functions

lookup_symbol is often called with user input.  Consequently, any
function called from lookup_symbol{,_in_language} should attempt to
deal with malformed input gracefully.  After all, malformed user
input is not a programming/API error.

This patch does not attempt to find/correct all instances of this.  It
only fixes locations in the code that trigger test suite failures.

This patch fixes PR breakpoints/18303, "Assertion: -breakpoint-insert
with windows paths of file in non-current directory".

The patch includes three new tests related to this.  One is just
gdb.linespec/ls-errs.exp copied and converted to use C++ instead of C, and
to add a case using a file name containing a Windows-style logical drive
specifier.  The others include an MI test to provide a regression test for
the specific case reported in PR 18303, and a C++ test for proper error
handling of access to a program variable when using a file scope specifier
that refers to a non-existent file.

Tested on x86_64 native Linux.

gdb/ChangeLog
2016-01-28  Keith Seitz  <keiths@redhat.com>

	PR breakpoints/18303
	* cp-namespace.c (cp_lookup_bare_symbol): Change assertion to
	look for "::" instead of simply ":".
	(cp_search_static_and_baseclasses): Return null_block_symbol for
	malformed input.
	Remove assertions.
	* cp-support.c (cp_find_first_component_aux): Do not return
	a prefix length for ':' unless the next character is also ':'.

gdb/testsuite/ChangeLog
2016-01-28  Don Breazeal  <donb@codesourcery.com>

	* gdb.cp/scope-err.cc: New test program.
	* gdb.cp/scope-err.exp: New test script.
	* gdb.linespec/ls-errs.c (myfunction): Expanded to have multiple
	lines and "set breakpoint here" comment.
	* gdb.linespec/ls-errs.exp: Added C++ testing and new test case.
	Fixed some whitespace and format issues.
	* gdb.mi/mi-linespec-err-cp.cc: New test program.
	* gdb.mi/mi-linespec-err-cp.exp: New test script.

2 files changed, 84 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.cp/scope-err.cc b/gdb/testsuite/gdb.cp/scope-err.cc
new file mode 100644
index 0000000..19c92d8
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/scope-err.cc
@@ -0,0 +1,35 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2016 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+myfunction (int aa)
+{
+  int i;
+
+  i = aa + 42;
+  return i;    /* set breakpoint here */
+}
+
+int
+main (void)
+{
+  int a;
+
+  a = myfunction (a);
+
+  return a;
+}
diff --git a/gdb/testsuite/gdb.cp/scope-err.exp b/gdb/testsuite/gdb.cp/scope-err.exp
new file mode 100644
index 0000000..b197829
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/scope-err.exp
@@ -0,0 +1,49 @@
+# Copyright 2012-2016 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Tests for linespec errors with C++.
+# Derived from gdb.linespec/ls-errs.exp.
+
+if {[skip_cplus_tests]} {
+    continue
+}
+
+standard_testfile .cc
+set exefile $testfile
+
+if {[prepare_for_testing $testfile $exefile $srcfile {debug c++}]} {
+    return -1
+}
+
+if {![runto_main]} {
+    fail "Can't run to main"
+    return 0
+}
+
+# Run to a location in the file.
+set bp_location [gdb_get_line_number "set breakpoint here"]
+
+gdb_test "break $srcfile:$bp_location" \
+    "Breakpoint.*at.* file .*$srcfile, line $bp_location\\." \
+    "breakpoint line number in file"
+
+gdb_continue_to_breakpoint "$bp_location"
+
+# Try to access a variable using scope that is a non-existent filename
+# with a Windows-style logical drive in the name.
+set nonexistent_file C:/does/not/exist.cc
+gdb_test "print '$nonexistent_file'::var" \
+	 ".*No symbol \"$nonexistent_file\" in current context.*" \
+	 "print var from \"$nonexistent_file\""