[PATCH] D42745: [analyzer] Add support for __builtin_constant_p to BuiltinFunctionChecker

[Felix Kostenzer via Phabricator via cfe-commits]

sp4r74n-117 created this revision.
sp4r74n-117 added reviewers: george.karpenkov, dcoughlin, dergachev.a.
sp4r74n-117 created this object with visibility "All Users".
Herald added subscribers: cfe-commits, a.sidorin, szepet, xazax.hun.

Added evaluation of __builtin_constant_p to the dedicated StaticAnalyzer checker along with a test case.

Tested via: make clang-test


Repository:
  rC Clang

https://reviews.llvm.org/D42745

Files:
  lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
  test/Analysis/builtin-functions.cpp


Index: test/Analysis/builtin-functions.cpp
===================================================================
--- test/Analysis/builtin-functions.cpp
+++ test/Analysis/builtin-functions.cpp
@@ -64,3 +64,18 @@
                                     // 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)); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(i)); // expected-warning {{FALSE}}
+  clang_analyzer_eval(__builtin_constant_p(j)); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(k)); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(i + 42)); // expected-warning {{FALSE}}
+  clang_analyzer_eval(__builtin_constant_p(j + 42)); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(k + 42)); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(" ")); // expected-warning {{TRUE}}
+  clang_analyzer_eval(__builtin_constant_p(test_constant_p)); // expected-warning {{FALSE}}
+}
Index: lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
+++ lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
@@ -113,6 +113,24 @@
     C.addTransition(state->BindExpr(CE, LCtx, V));
     return true;
   }
+
+  case Builtin::BI__builtin_constant_p: {
+    SVal V;
+    SValBuilder& SVB = C.getSValBuilder();
+
+    llvm::APSInt Result;
+    // Model semantics as 'A return of 0 does not indicate that the value is
+    // not a constant, but merely that GCC cannot prove it is a constant [...]'
+    if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) {
+      SVB.getBasicValueFactory().getAPSIntType(CE->getType()).apply(Result);
+      V = SVB.makeIntVal(Result);
+    }
+    else
+      V = SVB.makeZeroVal(CE->getType());
+
+    C.addTransition(state->BindExpr(CE, LCtx, V));
+    return true;
+  }
   }
 }
 


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