[analyzer] Treat more const variables and fields as known contants.

When loading from a variable or a field that is declared as constant,
the analyzer will try to inspect its initializer and constant-fold it.
Upon success, the analyzer would skip normal load and return the respective
constant.

The new behavior also applies to fields/elements of brace-initialized structures
and arrays.

Patch by Rafael Stahl!

Differential Revision: https://reviews.llvm.org/D45774

llvm-svn: 331556

1 files changed, 111 insertions, 0 deletions

diff --git a/clang/test/Analysis/globals.cpp b/clang/test/Analysis/globals.cpp
new file mode 100644
index 00000000000..5bbb241bdcf
--- /dev/null
+++ b/clang/test/Analysis/globals.cpp
@@ -0,0 +1,111 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -verify %s
+
+
+static const unsigned long long scull = 0;
+void static_int()
+{
+    *(int*)scull = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+const unsigned long long cull = 0;
+void const_int()
+{
+    *(int*)cull = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+static int * const spc = 0;
+void static_ptr()
+{
+    *spc = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+int * const pc = 0;
+void const_ptr()
+{
+    *pc = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+const unsigned long long cull_nonnull = 4;
+void nonnull_int()
+{
+    *(int*)(cull_nonnull - 4) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+int * const pc_nonnull = (int*)sizeof(int);
+void nonnull_ptr()
+{
+    *(pc_nonnull - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+int * const constcast = const_cast<int * const>((int*)sizeof(int));
+void cast1()
+{
+    *(constcast - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+int * const recast = reinterpret_cast<int*>(sizeof(int));
+void cast2()
+{
+    *(recast - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+int * const staticcast = static_cast<int * const>((int*)sizeof(int));
+void cast3()
+{
+    *(staticcast - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+struct Foo { int a; };
+Foo * const dyncast = dynamic_cast<Foo * const>((Foo*)sizeof(Foo));
+void cast4()
+{
+    // Do not handle dynamic_cast for now, because it may change the pointer value.
+    (dyncast - 1)->a = 0; // no-warning
+}
+
+typedef int * const intptrconst;
+int * const funccast = intptrconst(sizeof(int));
+void cast5()
+{
+    *(funccast - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+struct S1
+{
+    int * p;
+};
+const S1 s1 = {
+    .p = (int*)sizeof(int)
+};
+void conststruct()
+{
+    *(s1.p - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+struct S2
+{
+    int * const p;
+};
+S2 s2 = {
+    .p = (int*)sizeof(int)
+};
+void constfield()
+{
+    *(s2.p - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+int * const parr[1] = { (int*)sizeof(int) };
+void constarr()
+{
+    *(parr[0] - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}
+
+struct S3
+{
+    int * p = (int*)sizeof(int);
+};
+void recordinit()
+{
+    S3 s3;
+    *(s3.p - 1) = 0; // expected-warning{{Dereference of null pointer}}
+}