[test] Fix plugin tests

Recommit of r361790 that was temporarily reverted in r361793 due to bot breakage.

Summary:
The following changes were required to fix these tests:

1) Change LLVM_ENABLE_PLUGINS to an option and move it to
   llvm/CMakeLists.txt with an appropriate default -- which matches
   the original default behavior.

2) Move the plugins directory from clang/test/Analysis
   clang/lib/Analysis.  It's not enough to add an exclude to the
   lit.local.cfg file because add_lit_testsuites recurses the tree and
   automatically adds the appropriate `check-` targets, which don't
   make sense for the plugins because they aren't tests and don't
   have `RUN` statements.

   Here's a list of the `clang-check-anlysis*` targets with this
   change:

```
  $ ninja -t targets all| sed -n "s/.*\/\(check[^:]*\):.*/\1/p" | sort -u | grep clang-analysis
  check-clang-analysis
  check-clang-analysis-checkers
  check-clang-analysis-copypaste
  check-clang-analysis-diagnostics
  check-clang-analysis-engine
  check-clang-analysis-exploration_order
  check-clang-analysis-html_diagnostics
  check-clang-analysis-html_diagnostics-relevant_lines
  check-clang-analysis-inlining
  check-clang-analysis-objc
  check-clang-analysis-unified-sources
  check-clang-analysis-z3
```

3) Simplify the logic and only include the subdirectories under
   clang/lib/Analysis/plugins if LLVM_ENABLE_PLUGINS is set.

Reviewed By: NoQ

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D62445

llvm-svn: 362328

1 files changed, 54 insertions, 0 deletions

diff --git a/clang/lib/Analysis/plugins/SampleAnalyzer/MainCallChecker.cpp b/clang/lib/Analysis/plugins/SampleAnalyzer/MainCallChecker.cpp
new file mode 100644
index 00000000000..8bd4085108e
--- /dev/null
+++ b/clang/lib/Analysis/plugins/SampleAnalyzer/MainCallChecker.cpp
@@ -0,0 +1,54 @@
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "clang/StaticAnalyzer/Frontend/CheckerRegistry.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class MainCallChecker : public Checker<check::PreStmt<CallExpr>> {
+  mutable std::unique_ptr<BugType> BT;
+
+public:
+  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
+};
+} // end anonymous namespace
+
+void MainCallChecker::checkPreStmt(const CallExpr *CE,
+                                   CheckerContext &C) const {
+  const Expr *Callee = CE->getCallee();
+  const FunctionDecl *FD = C.getSVal(Callee).getAsFunctionDecl();
+
+  if (!FD)
+    return;
+
+  // Get the name of the callee.
+  IdentifierInfo *II = FD->getIdentifier();
+  if (!II) // if no identifier, not a simple C function
+    return;
+
+  if (II->isStr("main")) {
+    ExplodedNode *N = C.generateErrorNode();
+    if (!N)
+      return;
+
+    if (!BT)
+      BT.reset(new BugType(this, "call to main", "example analyzer plugin"));
+
+    std::unique_ptr<BugReport> report =
+        llvm::make_unique<BugReport>(*BT, BT->getName(), N);
+    report->addRange(Callee->getSourceRange());
+    C.emitReport(std::move(report));
+  }
+}
+
+// Register plugin!
+extern "C" void clang_registerCheckers(CheckerRegistry &registry) {
+  registry.addChecker<MainCallChecker>(
+      "example.MainCallChecker", "Disallows calls to functions called main",
+      "");
+}
+
+extern "C" const char clang_analyzerAPIVersionString[] =
+    CLANG_ANALYZER_API_VERSION_STRING;