Split a chunk of -Wconditional-uninitialized warnings out into a separate flag,

-Wsometimes-uninitialized. This detects cases where an explicitly-written branch
inevitably leads to an uninitialized variable use (so either the branch is dead
code or there is an uninitialized use bug).

This chunk of warnings tentatively lives within -Wuninitialized, in order to
give it more visibility to existing Clang users.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157458 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 57 insertions, 3 deletions

diff --git a/include/clang/Analysis/Analyses/UninitializedValues.h b/include/clang/Analysis/Analyses/UninitializedValues.h
index 4ee66986be..45ce4de1f8 100644
--- a/include/clang/Analysis/Analyses/UninitializedValues.h
+++ b/include/clang/Analysis/Analyses/UninitializedValues.h
@@ -15,6 +15,8 @@
 #ifndef LLVM_CLANG_UNINIT_VALS_H
 #define LLVM_CLANG_UNINIT_VALS_H
 
+#include "llvm/ADT/SmallVector.h"
+
 namespace clang {
 
 class AnalysisDeclContext;
@@ -23,15 +25,67 @@ class DeclContext;
 class Expr;
 class VarDecl;
 
+/// A use of a variable, which might be uninitialized.
+class UninitUse {
+public:
+  struct Branch {
+    const Stmt *Terminator;
+    unsigned Output;
+  };
+
+private:
+  /// The expression which uses this variable.
+  const Expr *User;
+
+  /// Does this use always see an uninitialized value?
+  bool AlwaysUninit;
+
+  /// This use is always uninitialized if it occurs after any of these branches
+  /// is taken.
+  llvm::SmallVector<Branch, 2> UninitBranches;
+
+public:
+  UninitUse(const Expr *User, bool AlwaysUninit) :
+    User(User), AlwaysUninit(AlwaysUninit) {}
+
+  void addUninitBranch(Branch B) {
+    UninitBranches.push_back(B);
+  }
+
+  /// Get the expression containing the uninitialized use.
+  const Expr *getUser() const { return User; }
+
+  /// The kind of uninitialized use.
+  enum Kind {
+    /// The use might be uninitialized.
+    Maybe,
+    /// The use is uninitialized whenever a certain branch is taken.
+    Sometimes,
+    /// The use is always uninitialized.
+    Always
+  };
+
+  /// Get the kind of uninitialized use.
+  Kind getKind() const {
+    return AlwaysUninit ? Always :
+           !branch_empty() ? Sometimes : Maybe;
+  }
+
+  typedef llvm::SmallVectorImpl<Branch>::const_iterator branch_iterator;
+  /// Branches which inevitably result in the variable being used uninitialized.
+  branch_iterator branch_begin() const { return UninitBranches.begin(); }
+  branch_iterator branch_end() const { return UninitBranches.end(); }
+  bool branch_empty() const { return UninitBranches.empty(); }
+};
+
 class UninitVariablesHandler {
 public:
   UninitVariablesHandler() {}
   virtual ~UninitVariablesHandler();
 
   /// Called when the uninitialized variable is used at the given expression.
-  virtual void handleUseOfUninitVariable(const Expr *ex,
-                                         const VarDecl *vd,
-                                         bool isAlwaysUninit) {}
+  virtual void handleUseOfUninitVariable(const VarDecl *vd,
+                                         const UninitUse &use) {}
 
   /// Called when the uninitialized variable analysis detects the
   /// idiom 'int x = x'.  All other uses of 'x' within the initializer