[analyzer] DeadStores: Add a crude suppression files generated by DriverKit IIG.

IIG is a replacement for MIG in DriverKit: IIG is autogenerating C++ code.
Suppress dead store warnings on such code, as the tool seems to be producing
them regularly, and the users of IIG are not in position to address these
warnings, as they don't control the autogenerated code. IIG-generated code
is identified by looking at the comments at the top of the file.

Differential Revision: https://reviews.llvm.org/D63118

llvm-svn: 363892

3 files changed, 55 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
index e316c9120b2..b6fa47e4699 100644
--- a/clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
@@ -160,6 +160,26 @@ public:
     return InEH->count(D);
   }
 
+  bool isSuppressed(SourceRange R) {
+    SourceManager &SMgr = Ctx.getSourceManager();
+    SourceLocation Loc = R.getBegin();
+    if (!Loc.isValid())
+      return false;
+
+    FileID FID = SMgr.getFileID(Loc);
+    bool Invalid = false;
+    StringRef Data = SMgr.getBufferData(FID, &Invalid);
+    if (Invalid)
+      return false;
+
+    // Files autogenerated by DriverKit IIG contain some dead stores that
+    // we don't want to report.
+    if (Data.startswith("/* iig generated from"))
+      return true;
+
+    return false;
+  }
+
   void Report(const VarDecl *V, DeadStoreKind dsk,
               PathDiagnosticLocation L, SourceRange R) {
     if (Escaped.count(V))
@@ -175,6 +195,9 @@ public:
     if (!reachableCode->isReachable(currentBlock))
       return;
 
+    if (isSuppressed(R))
+      return;
+
     SmallString<64> buf;
     llvm::raw_svector_ostream os(buf);
     const char *BugType = nullptr;
diff --git a/clang/test/Analysis/deadstores-driverkit.cpp b/clang/test/Analysis/deadstores-driverkit.cpp
new file mode 100644
index 00000000000..446821b32ca
--- /dev/null
+++ b/clang/test/Analysis/deadstores-driverkit.cpp
@@ -0,0 +1,24 @@
+/* iig generated from SomethingSomething.iig */
+
+// The comment above is the whole point of the test.
+// That's how the suppression works.
+// It needs to be on the top.
+// Run-lines can wait.
+
+// RUN: %clang_analyze_cc1 -w -triple x86_64-apple-driverkit19.0 \
+// RUN:   -analyzer-checker=deadcode -verify %s
+
+// expected-no-diagnostics
+
+#include "os_object_base.h"
+
+class OSSomething {
+  kern_return_t Invoke(const IORPC);
+  void foo(OSDispatchMethod supermethod) {
+    kern_return_t ret;
+    IORPC rpc;
+    // Test the DriverKit specific suppression in the dead stores checker.
+    if (supermethod) ret = supermethod((OSObject *)this, rpc); // no-warning
+    else             ret = ((OSObject *)this)->Invoke(rpc); // no-warning
+  }
+};
diff --git a/clang/test/Analysis/os_object_base.h b/clang/test/Analysis/os_object_base.h
index 37a3fc07df7..4698185f2b3 100644
--- a/clang/test/Analysis/os_object_base.h
+++ b/clang/test/Analysis/os_object_base.h
@@ -19,6 +19,9 @@
 
 using size_t = decltype(sizeof(int));
 
+typedef int kern_return_t;
+struct IORPC {};
+
 struct OSMetaClass;
 
 struct OSMetaClassBase {
@@ -37,8 +40,13 @@ struct OSMetaClassBase {
 
   virtual void free();
   virtual ~OSMetaClassBase(){};
+
+  kern_return_t Invoke(IORPC invoke);
 };
 
+typedef kern_return_t (*OSDispatchMethod)(OSMetaClassBase *self,
+                                          const IORPC rpc);
+
 struct OSObject : public OSMetaClassBase {
   virtual ~OSObject(){}