Fix asserts with side-effects (per Keegan McAllister)

src/util/Makefile.am

@@ -2,4 +2,4 @@ AM_CXXFLAGS = $(WARNING_CXXFLAGS) $(PICKY_CXXFLAGS) -fno-default-inline -pipe
 
 noinst_LIBRARIES = libmoshutil.a
 
-libmoshutil_a_SOURCES = swrite.cc swrite.h dos_assert.h
+libmoshutil_a_SOURCES = swrite.cc swrite.h dos_assert.h fatal_assert.h

src/util/fatal_assert.h

@@ -0,0 +1,38 @@
+/*
+    Mosh: the mobile shell
+    Copyright 2012 Keith Winstein
+
+    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/>.
+*/
+
+#ifndef FATAL_ASSERT_HPP
+#define FATAL_ASSERT_HPP
+
+#include <stdio.h>
+#include <stdlib.h>
+
+static void fatal_error( const char *expression, const char *file, int line, const char *function )
+{
+  char buffer[ 2048 ];
+  snprintf( buffer, 2048, "Fatal assertion failure in function %s at %s:%d, failed test: %s\n",
+	    function, file, line, expression );
+  exit( 2 );
+}
+
+#define fatal_assert(expr)						\
+  ((expr)								\
+   ? (void)0								\
+   : fatal_error (__STRING(expr), __FILE__, __LINE__, __PRETTY_FUNCTION__ ))
+
+#endif