r259345 - [analyzer] Use a wider integer type for an array index.

[Artem Dergachev via cfe-commits]

Author: dergachev
Date: Mon Feb  1 03:29:17 2016
New Revision: 259345

URL: http://llvm.org/viewvc/llvm-project?rev=259345&view=rev
Log:
[analyzer] Use a wider integer type for an array index.

Avoids unexpected overflows while performing pointer arithmetics in 64-bit code.
Moreover, neither PointerDiffType nor 'int' can be used as a common array index
type because arrays may have size (and indexes) more than PTRDIFF_MAX but less
than SIZE_MAX.

Patch by Aleksei Sidorin!

Differential Revision: http://reviews.llvm.org/D16063

Added:
    cfe/trunk/test/Analysis/index-type.c
Modified:
    cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h

Modified: cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h?rev=259345&r1=259344&r2=259345&view=diff
==============================================================================
--- cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h (original)
+++ cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h Mon Feb  1 03:29:17 2016
@@ -65,7 +65,7 @@ public:
       SymMgr(context, BasicVals, alloc),
       MemMgr(context, alloc),
       StateMgr(stateMgr),
-      ArrayIndexTy(context.IntTy),
+      ArrayIndexTy(context.LongLongTy),
       ArrayIndexWidth(context.getTypeSize(ArrayIndexTy)) {}
 
   virtual ~SValBuilder() {}

Added: cfe/trunk/test/Analysis/index-type.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/index-type.c?rev=259345&view=auto
==============================================================================
--- cfe/trunk/test/Analysis/index-type.c (added)
+++ cfe/trunk/test/Analysis/index-type.c Mon Feb  1 03:29:17 2016
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -analyze -analyzer-checker=core,alpha.security.ArrayBoundV2 -verify %s
+// RUN: %clang_cc1 -triple i386-apple-darwin10 -analyze -analyzer-checker=core,alpha.security.ArrayBoundV2 -DM32 -verify %s
+// expected-no-diagnostics
+
+#define UINT_MAX (~0u)
+
+#ifdef M32
+
+#define X86_ARRAY_SIZE (UINT_MAX/2 + 4)
+
+void testIndexTooBig() {
+  char arr[X86_ARRAY_SIZE];
+  char *ptr = arr + UINT_MAX/2;
+  ptr += 2;  // index shouldn't overflow
+  *ptr = 42; // no-warning
+}
+
+#else // 64-bit tests
+
+#define ARRAY_SIZE 0x100000000
+
+void testIndexOverflow64() {
+  char arr[ARRAY_SIZE];
+  char *ptr = arr + UINT_MAX/2;
+  ptr += 2;  // don't overflow 64-bit index
+  *ptr = 42; // no-warning
+}
+
+#define ULONG_MAX (~0ul)
+#define BIG_INDEX (ULONG_MAX/16)
+
+void testIndexTooBig64() {
+  char arr[ULONG_MAX/8-1];
+  char *ptr = arr + BIG_INDEX;
+  ptr += 2;  // don't overflow 64-bit index
+  *ptr = 42; // no-warning
+}
+
+#endif