[analyzer] Add support for __builtin_constant_p.

This builtin is evaluated in compile time. But in the analyzer we don't yet
automagically evaluate all calls that can be evaluated in compile time.

Patch by Felix Kostenzer!

Differential Revision: https://reviews.llvm.org/D42745

llvm-svn: 324789

2 files changed, 19 insertions, 1 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
index 93c9bfa043a..0e781d08e24 100644
--- a/clang/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
@@ -96,7 +96,8 @@ bool BuiltinFunctionChecker::evalCall(const CallExpr *CE,
     return true;
   }
 
-  case Builtin::BI__builtin_object_size: {
+  case Builtin::BI__builtin_object_size:
+  case Builtin::BI__builtin_constant_p: {
     // This must be resolvable at compile time, so we defer to the constant
     // evaluator for a value.
     SVal V = UnknownVal();
diff --git a/clang/test/Analysis/builtin-functions.cpp b/clang/test/Analysis/builtin-functions.cpp
index 2c195025114..19984963b4f 100644
--- a/clang/test/Analysis/builtin-functions.cpp
+++ b/clang/test/Analysis/builtin-functions.cpp
@@ -64,3 +64,20 @@ void g(int i) {
                                     // We give up the analysis on this path.
   }
 }
+
+void test_constant_p() {
+  int i = 1;
+  const int j = 2;
+  constexpr int k = 3;
+  clang_analyzer_eval(__builtin_constant_p(42) == 1); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(i) == 0); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(j) == 1); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(k) == 1); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(i + 42) == 0); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(j + 42) == 1); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(k + 42) == 1); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(" ") == 1); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(test_constant_p) == 0); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(k - 3) == 0); // expected-warning {{FALSE}}
+  clang_analyzer_eval(__builtin_constant_p(k - 3) == 1); // expected-warning {{TRUE}}
+}