Convert root_cause test to use Clang's built-in diagnostic verifier.

This means we now verify the line numbers of the diagnostics for free,
which would have been a pain with the existing CHECK-DAG system.

- Make the 3c tool accept a -verify option analogous to that of `clang
  -cc1` to verify diagnostics against `// expected-warning` comments.
  Currently, this applies only to the rewriting phase.

- Fix a few mistakes in the expected diagnostics in the root_cause test.

Author: mattmccutchen-cci

clang/include/clang/3C/3C.h

@@ -65,6 +65,11 @@ struct _3COptions {
   bool RemoveItypes;
   bool ForceItypes;
 #endif
+
+  // Currently applies only to the rewriting phase (because it is the only phase
+  // that generates diagnostics, except for the declaration merging diagnostics
+  // that are currently fatal) and uses the default "expected" prefix.
+  bool VerifyDiagnosticOutput;
 };
 
 // The main interface exposed by the 3C to interact with the tool.

clang/lib/3C/3C.cpp

@@ -54,6 +54,7 @@ bool DisableCCTypeChecker;
 bool WarnRootCause;
 bool WarnAllRootCause;
 std::set<std::string> FilePaths;
+bool VerifyDiagnosticOutput;
 
 #ifdef FIVE_C
 bool RemoveItypes;
@@ -95,19 +96,39 @@ class RewriteAction : public ASTFrontendAction {
 
 template <typename T>
 std::unique_ptr<FrontendActionFactory>
-newFrontendActionFactoryA(ProgramInfo &I) {
+newFrontendActionFactoryA(ProgramInfo &I, bool VerifyTheseDiagnostics = false) {
   class ArgFrontendActionFactory : public FrontendActionFactory {
   public:
-    explicit ArgFrontendActionFactory(ProgramInfo &I) : Info(I) {}
+    explicit ArgFrontendActionFactory(ProgramInfo &I,
+                                      bool VerifyTheseDiagnostics)
+        : Info(I), VerifyTheseDiagnostics(VerifyTheseDiagnostics) {}
 
     FrontendAction *create() override { return new T(Info); }
 
+    bool runInvocation(std::shared_ptr<CompilerInvocation> Invocation,
+                       FileManager *Files,
+                       std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+                       DiagnosticConsumer *DiagConsumer) override {
+      if (VerifyTheseDiagnostics) {
+        // Mirroring the logic of clang::ParseDiagnosticArgs in
+        // clang/lib/Frontend/CompilerInvocation.cpp. In particular, note that
+        // VerifyPrefixes is assumed to be sorted, in case we add more in the
+        // future.
+        DiagnosticOptions &DiagOpts = Invocation->getDiagnosticOpts();
+        DiagOpts.VerifyDiagnostics = true;
+        DiagOpts.VerifyPrefixes.push_back("expected");
+      }
+      return FrontendActionFactory::runInvocation(
+          Invocation, Files, PCHContainerOps, DiagConsumer);
+    }
+
   private:
     ProgramInfo &Info;
+    bool VerifyTheseDiagnostics;
   };
 
   return std::unique_ptr<FrontendActionFactory>(
-      new ArgFrontendActionFactory(I));
+      new ArgFrontendActionFactory(I, VerifyTheseDiagnostics));
 }
 
 ArgumentsAdjuster getIgnoreCheckedPointerAdjuster() {
@@ -192,6 +213,7 @@ _3CInterface::_3CInterface(const struct _3COptions &CCopt,
   AllocatorFunctions = CCopt.AllocatorFunctions;
   WarnRootCause = CCopt.WarnRootCause || CCopt.WarnAllRootCause;
   WarnAllRootCause = CCopt.WarnAllRootCause;
+  VerifyDiagnosticOutput = CCopt.VerifyDiagnosticOutput;
 
 #ifdef FIVE_C
   RemoveItypes = CCopt.RemoveItypes;
@@ -368,7 +390,7 @@ bool _3CInterface::writeConvertedFileToDisk(const std::string &FilePath) {
     Tool.appendArgumentsAdjuster(getIgnoreCheckedPointerAdjuster());
     std::unique_ptr<ToolAction> RewriteTool =
         newFrontendActionFactoryA<RewriteAction<RewriteConsumer, ProgramInfo>>(
-            GlobalProgramInfo);
+            GlobalProgramInfo, VerifyDiagnosticOutput);
 
     if (RewriteTool) {
       int ToolExitCode = Tool.run(RewriteTool.get());
@@ -388,7 +410,7 @@ bool _3CInterface::writeAllConvertedFilesToDisk() {
   // Rewrite the input files
   std::unique_ptr<ToolAction> RewriteTool =
       newFrontendActionFactoryA<RewriteAction<RewriteConsumer, ProgramInfo>>(
-          GlobalProgramInfo);
+          GlobalProgramInfo, VerifyDiagnosticOutput);
   if (RewriteTool) {
     int ToolExitCode = Tool.run(RewriteTool.get());
     if (ToolExitCode != 0)

clang/test/3C/root_cause.c

@@ -1,55 +1,43 @@
-// RUN: 3c -extra-arg="-Wno-everything" -alltypes -warn-root-cause %s 2>&1 >%t.unused | FileCheck %s
+// RUN: 3c -extra-arg="-Wno-everything" -verify -alltypes -warn-root-cause %s
 
 // This test is unusual in that it checks for the errors in the code
 
 #include <stddef.h>
 extern _Itype_for_any(T) void *malloc(size_t size) : itype(_Array_ptr<T>) byte_count(size);
 
-void *x;
-// CHECK-DAG: Default void* type
+void *x; // expected-warning {{Default void* type}}
 
 void test0() {
   int *a;
   char *b;
-  a = b;
-  // CHECK-DAG: Cast from int * to char *
+  a = b; // expected-warning {{Cast from char * to int *}}
 
   int *c;
-  (char*) c;
-  // CHECK-DAG: Cast from int * to char *
+  (char*) c; // expected-warning {{Cast from int * to char *}}
 
 
   int *e;
   char *f;
-  f = (char*) e;
-  // CHECK-DAG: Cast from char * to int *
+  f = (char*) e; // expected-warning {{Cast from int * to char *}}
 }
 
 void test1() {
   int a;
   int *b;
-  b = malloc(sizeof(int));
+  b = malloc(sizeof(int)); // expected-warning {{Bad pointer type solution}}
   b[0] = 1;
 
   union u {
-    int *a;
-    // CHECK-DAG: Union or external struct field encountered
-    int *b;
-    // CHECK-DAG: Union or external struct field encountered
+    int *a; // expected-warning {{Union or external struct field encountered}}
+    int *b; // expected-warning {{Union or external struct field encountered}}
   };
 
   void (*c)(void);
-  c++;
-  // CHECK-DAG: Pointer arithmetic performed on a function pointer
+  c++; // expected-warning {{Pointer arithmetic performed on a function pointer}}
 
-  int *d = malloc(1);
-  // CHECK-DAG: Unsafe call to allocator function
+  int *d = malloc(1); // expected-warning {{Unsafe call to allocator function}}
 }
 
-extern int *glob;
-// CHECK-DAG: External global variable glob has no definition
+extern int *glob; // expected-warning {{External global variable glob has no definition}}
 
-void (*f)(void *);
-// CHECK-DAG: Default void* type
-
-// CHECK-DAG: 11 warnings generated.
+void (*f)(void *); // expected-warning {{Default void* type}}

clang/tools/3c/3CStandalone.cpp

@@ -121,6 +121,20 @@ static cl::opt<bool>
                                  "even those unlikely to be interesting."),
                         cl::init(false), cl::cat(_3CCategory));
 
+// https://clang.llvm.org/doxygen/classclang_1_1VerifyDiagnosticConsumer.html#details
+//
+// Analogous to the -verify option of `clang -cc1`, but currently applies only
+// to the rewriting phase (because it is the only phase that generates
+// diagnostics, except for the declaration merging diagnostics that are
+// currently fatal). No checking of diagnostics from the other phases is
+// performed. We cannot simply have the caller pass `-extra-arg=-Xclang
+// -extra-arg=-verify` because that would expect each phase to produce the same
+// set of diagnostics.
+static cl::opt<bool> OptVerifyDiagnosticOutput(
+    "verify",
+    cl::desc("Verify diagnostic output (for automated testing of 3C)."),
+    cl::init(false), cl::cat(_3CCategory), cl::Hidden);
+
 #ifdef FIVE_C
 static cl::opt<bool> OptRemoveItypes(
     "remove-itypes",
@@ -161,6 +175,7 @@ int main(int argc, const char **argv) {
   CcOptions.DisableCCTypeChecker = OptDiableCCTypeChecker;
   CcOptions.WarnRootCause = OptWarnRootCause;
   CcOptions.WarnAllRootCause = OptWarnAllRootCause;
+  CcOptions.VerifyDiagnosticOutput = OptVerifyDiagnosticOutput;
 
 #ifdef FIVE_C
   CcOptions.RemoveItypes = OptRemoveItypes;