[PATCH] D16063: [Analyzer] Use a wider integer type for an array index

[Aleksei Sidorin via cfe-commits]

a.sidorin created this revision.
a.sidorin added reviewers: zaks.anna, dcoughlin, xazax.hun.
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a.sidorin set the repository for this revision to rL LLVM.

Currently, a default index type in CSA is 'int'. However, this assumption seems to be incorrect for 64-bit platforms where index may be 64-bit as well as the array size. For example, it leads to unexpected overflows while performing pointer arithmetics. Moreover, PointerDiffType and 'int' cannot be used as a common array index type because arrays may have size (and indexes) more than PTRDIFF_MAX but less than SIZE_MAX. Since maximum array size for 64 bits is SIZE_MAX/8, I propose to use 'long long' as a common index type, although it looks a bit hacky for 32 bit.

Repository:
  rL LLVM

http://reviews.llvm.org/D16063

Files:
  include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
  test/Analysis/index-type.c

Index: test/Analysis/index-type.c
===================================================================
--- /dev/null
+++ test/Analysis/index-type.c
@@ -0,0 +1,38 @@
+// 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_ARRAY_SIZE 0x9000000000000000
+void testIndexTooBig64() {
+  char arr[ULONG_MAX/8-1];
+  char *ptr = arr + ULONG_MAX;
+  ptr += 2;  // don't overflow 64-bit index
+  *ptr = 42; // no-warning
+}
+
+#endif
Index: include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
===================================================================
--- include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
+++ include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
@@ -65,7 +65,7 @@
       SymMgr(context, BasicVals, alloc),
       MemMgr(context, alloc),
       StateMgr(stateMgr),
-      ArrayIndexTy(context.IntTy),
+      ArrayIndexTy(context.LongLongTy),
       ArrayIndexWidth(context.getTypeSize(ArrayIndexTy)) {}
 
   virtual ~SValBuilder() {}


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