tui-disasm: Fix window content buffer overrun

A user reported a GDB crash with TUI when trying to debug a function
with a long demangled C++ method name.  It turned out that the logic for
displaying the TUI disassembly window has a bug that can cause a buffer
overrun, possibly overwriting GDB-internal data structures.  In
particular, the logic performs an unguarded strcpy.

Another (harmless) bug in tui_alloc_source_buffer causes the buffer to
be two lines longer than needed.  This may have made the crash appear
less frequently.

gdb/ChangeLog:

	* tui/tui-disasm.c (tui_set_disassem_content): Fix line buffer
	overrun due to unchecked strcpy.

gdb/testsuite/ChangeLog:

	* gdb.base/tui-layout.c: New file.
	* gdb.base/tui-layout.exp: Use tui-layout.c, to ensure that the
	disassembly window contains very long lines.

2 files changed, 61 insertions, 3 deletions

diff --git a/gdb/testsuite/gdb.base/tui-layout.c b/gdb/testsuite/gdb.base/tui-layout.c
new file mode 100644
index 0000000..4049f9b
--- /dev/null
+++ b/gdb/testsuite/gdb.base/tui-layout.c
@@ -0,0 +1,47 @@
+/* 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/>.  */
+
+#define LONGER_NAME(x) x ## x
+#define LONGER(x) LONGER_NAME(x)
+#define LONGNAME1 d_this_identifier_of_32_chars_an
+#define LONGNAME2 LONGER (LONGER (LONGER (LONGER (LONGER (LONGNAME1)))))
+
+/* Construct a long identifier name.  If SHORT_IDENTIFIERS is set, limit
+   it to 1024 chars.  */
+
+#ifdef SHORT_IDENTIFIERS
+#define LONGNAME3 LONGNAME2
+#else
+#define LONGNAME3 LONGER (LONGER (LONGER (LONGER (LONGER (LONGNAME2)))))
+#endif
+
+void LONGNAME3 (void);
+
+int
+main ()
+{
+  LONGNAME3 ();
+  return 0;
+}
+
+/* Function with a long name.  Placing it after main makes it more likely
+   to be shown in the disassembly window on startup.  */
+
+void
+LONGNAME3 (void)
+{
+}
diff --git a/gdb/testsuite/gdb.base/tui-layout.exp b/gdb/testsuite/gdb.base/tui-layout.exp
index 43b3a4f..d8cd228 100644
--- a/gdb/testsuite/gdb.base/tui-layout.exp
+++ b/gdb/testsuite/gdb.base/tui-layout.exp
@@ -13,12 +13,23 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-standard_testfile start.c
+standard_testfile
 
-if { [prepare_for_testing ${testfile}.exp ${testfile} $srcfile] } {
-    return -1
+set ccopts {debug quiet}
+if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "$binfile" \
+	  executable $ccopts] != "" } {
+    # Maybe the compiler can't handle arbitrarily long identfier names.
+    # Try with a shorter version.
+    lappend ccopts "additional_flags=-DSHORT_IDENTIFIERS"
+    if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "$binfile" \
+	      executable $ccopts] != "" } {
+	untested "compile"
+	return -1
+    }
 }
 
+clean_restart "$binfile"
+
 if {[skip_tui_tests]} {
     # TUI support is disabled.  Check for error message.
     gdb_test "layout asm" "Undefined command: \"layout\".  Try \"help\"."