From a97648b93846f163af262b9a0db684c7f5efc43f Mon Sep 17 00:00:00 2001
From: Gabor Marton <gabor.marton@ericsson.com>
Date: Thu, 10 Sep 2020 12:41:29 +0200
Subject: [PATCH] [analyzer][StdLibraryFunctionsChecker] Add better diagnostics

Differential Revision: https://reviews.llvm.org/D79431
---
 .../Checkers/StdLibraryFunctionsChecker.cpp        | 25 +++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index c6c37a8..f5ad809 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -126,6 +126,8 @@ class StdLibraryFunctionsChecker
     }
     ArgNo getArgNo() const { return ArgN; }
 
+    virtual StringRef getName() const = 0;
+
   protected:
     ArgNo ArgN; // Argument to which we apply the constraint.
 
@@ -152,6 +154,7 @@ class StdLibraryFunctionsChecker
     IntRangeVector Ranges;
 
   public:
+    StringRef getName() const override { return "Range"; }
     RangeConstraint(ArgNo ArgN, RangeKind Kind, const IntRangeVector &Ranges)
         : ValueConstraint(ArgN), Kind(Kind), Ranges(Ranges) {}
 
@@ -205,6 +208,7 @@ class StdLibraryFunctionsChecker
     ArgNo OtherArgN;
 
   public:
+    virtual StringRef getName() const override { return "Comparison"; };
     ComparisonConstraint(ArgNo ArgN, BinaryOperator::Opcode Opcode,
                          ArgNo OtherArgN)
         : ValueConstraint(ArgN), Opcode(Opcode), OtherArgN(OtherArgN) {}
@@ -221,6 +225,7 @@ class StdLibraryFunctionsChecker
     bool CannotBeNull = true;
 
   public:
+    StringRef getName() const override { return "NonNull"; }
     ProgramStateRef apply(ProgramStateRef State, const CallEvent &Call,
                           const Summary &Summary,
                           CheckerContext &C) const override {
@@ -272,6 +277,7 @@ class StdLibraryFunctionsChecker
     BinaryOperator::Opcode Op = BO_LE;
 
   public:
+    StringRef getName() const override { return "BufferSize"; }
     BufferSizeConstraint(ArgNo Buffer, llvm::APSInt BufMinSize)
         : ValueConstraint(Buffer), ConcreteSize(BufMinSize) {}
     BufferSizeConstraint(ArgNo Buffer, ArgNo BufSize)
@@ -466,6 +472,8 @@ class StdLibraryFunctionsChecker
       return *this;
     }
     Summary &ArgConstraint(ValueConstraintPtr VC) {
+      assert(VC->getArgNo() != Ret &&
+             "Arg constraint should not refer to the return value");
       ArgConstraints.push_back(VC);
       return *this;
     }
@@ -549,17 +557,24 @@ private:
   void initFunctionSummaries(CheckerContext &C) const;
 
   void reportBug(const CallEvent &Call, ExplodedNode *N,
-                 CheckerContext &C) const {
+                 const ValueConstraint *VC, CheckerContext &C) const {
     if (!ChecksEnabled[CK_StdCLibraryFunctionArgsChecker])
       return;
-    // TODO Add detailed diagnostic.
-    StringRef Msg = "Function argument constraint is not satisfied";
+    // TODO Add more detailed diagnostic.
+    std::string Msg =
+        (Twine("Function argument constraint is not satisfied, constraint: ") +
+         VC->getName().data() + ", ArgN: " + Twine(VC->getArgNo()))
+            .str();
     if (!BT_InvalidArg)
       BT_InvalidArg = std::make_unique<BugType>(
           CheckNames[CK_StdCLibraryFunctionArgsChecker],
           "Unsatisfied argument constraints", categories::LogicError);
     auto R = std::make_unique<PathSensitiveBugReport>(*BT_InvalidArg, Msg, N);
-    bugreporter::trackExpressionValue(N, Call.getArgExpr(0), *R);
+    bugreporter::trackExpressionValue(N, Call.getArgExpr(VC->getArgNo()), *R);
+
+    // Highlight the range of the argument that was violated.
+    R->addRange(Call.getArgSourceRange(VC->getArgNo()));
+
     C.emitReport(std::move(R));
   }
 };
@@ -696,7 +711,7 @@ void StdLibraryFunctionsChecker::checkPreCall(const CallEvent &Call,
     // The argument constraint is not satisfied.
     if (FailureSt && !SuccessSt) {
       if (ExplodedNode *N = C.generateErrorNode(NewState))
-        reportBug(Call, N, C);
+        reportBug(Call, N, Constraint.get(), C);
       break;
     } else {
       // We will apply the constraint even if we cannot reason about the
-- 
2.7.4