Index: test/Analysis/scan-build-isystem.h
===================================================================
--- /dev/null
+++ test/Analysis/scan-build-isystem.h
@@ -0,0 +1 @@
+// dummy file
\ No newline at end of file
Index: test/Analysis/scan-build-isystem.c
===================================================================
--- /dev/null
+++ test/Analysis/scan-build-isystem.c
@@ -0,0 +1,10 @@
+// RUN: perl %S/../../tools/scan-build/scan-build --use-analyzer %clang -o %t %clang_cc1 -isystem%S -fsyntax-only %s 2>&1
+// RUN: perl %S/../../tools/scan-build/scan-build --use-analyzer %clang -o %t %clang_cc1 -isystem %S -fsyntax-only %s 2>&1
+// ccc-analyzer has to correctly look up and include -isystem directory to avoid static analysis failures in scan-build.
+
+#include <scan-build-isystem.h>
+
+void f() {
+  int * i = 0;
+  *i = 1; // CHECK: Dereference of null pointer
+}
Index: tools/scan-build/ccc-analyzer
===================================================================
--- tools/scan-build/ccc-analyzer
+++ tools/scan-build/ccc-analyzer
@@ -576,10 +576,9 @@
   }
 
   # Compile mode flags.
-  if ($Arg =~ /^-[D,I,U,isystem](.*)$/) {
+  if ($Arg =~ /^-[D,I,U](.*)$/ || $Arg =~ /^-isystem(.*)$/) {
     my $Tmp = $Arg;
     if ($1 eq '') {
-      # FIXME: Check if we are going off the end.
       ++$i;
       $Tmp = $Arg . $ARGV[$i];
     }