[analyzer] Prevent misuses of -analyze-function

Sometimes when I pass the mentioned option I forget about passing the
parameter list for c++ sources.
It would be also useful newcomers to learn about this.

This patch introduces some logic checking common misuses involving
`-analyze-function`.

Reviewed-By: martong

Differential Revision: https://reviews.llvm.org/D118690

Author: Balazs Benics

clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp

@@ -501,6 +501,28 @@ static bool fileContainsString(StringRef Substring, ASTContext &C) {
   return Buffer.contains(Substring);
 }
 
+static void reportAnalyzerFunctionMisuse(const AnalyzerOptions &Opts,
+                                         const ASTContext &Ctx) {
+  llvm::errs() << "Every top-level function was skipped.\n";
+
+  if (!Opts.AnalyzerDisplayProgress)
+    llvm::errs() << "Pass the -analyzer-display-progress for tracking which "
+                    "functions are analyzed.\n";
+
+  bool HasBrackets =
+      Opts.AnalyzeSpecificFunction.find("(") != std::string::npos;
+
+  if (Ctx.getLangOpts().CPlusPlus && !HasBrackets) {
+    llvm::errs()
+        << "For analyzing C++ code you need to pass the function parameter "
+           "list: -analyze-function=\"foobar(int, _Bool)\"\n";
+  } else if (!Ctx.getLangOpts().CPlusPlus && HasBrackets) {
+    llvm::errs() << "For analyzing C code you shouldn't pass the function "
+                    "parameter list, only the name of the function: "
+                    "-analyze-function=foobar\n";
+  }
+}
+
 void AnalysisConsumer::runAnalysisOnTranslationUnit(ASTContext &C) {
   BugReporter BR(*Mgr);
   TranslationUnitDecl *TU = C.getTranslationUnitDecl();
@@ -537,6 +559,14 @@ void AnalysisConsumer::runAnalysisOnTranslationUnit(ASTContext &C) {
 
   BR.FlushReports();
   RecVisitorBR = nullptr;
+
+  // If the user wanted to analyze a specific function and the number of basic
+  // blocks analyzed is zero, than the user might not specified the function
+  // name correctly.
+  // FIXME: The user might have analyzed the requested function in Syntax mode,
+  // but we are unaware of that.
+  if (!Opts->AnalyzeSpecificFunction.empty() && NumFunctionsAnalyzed == 0)
+    reportAnalyzerFunctionMisuse(*Opts, *Ctx);
 }
 
 void AnalysisConsumer::reportAnalyzerProgress(StringRef S) {

clang/test/Analysis/analyze-function-guide.cpp

@@ -0,0 +1,74 @@
+int fizzbuzz(int x, bool y) {
+  return x + y;
+}
+
+// C++ but not uses parentheses in the '-analyze-function' option.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core \
+// RUN:   -analyze-function='missing_fn' -x c++ \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-CXX
+//
+// CHECK-CXX:      Every top-level function was skipped.
+// CHECK-CXX-NEXT: Pass the -analyzer-display-progress for tracking which functions are analyzed.
+// CHECK-CXX-NEXT: For analyzing C++ code you need to pass the function parameter list: -analyze-function="foobar(int, _Bool)"
+
+// C but uses parentheses in the '-analyze-function' option.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core \
+// RUN:   -analyze-function='missing_fn()' -x c -Dbool=_Bool \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-C
+//
+// CHECK-C:      Every top-level function was skipped.
+// CHECK-C-NEXT: Pass the -analyzer-display-progress for tracking which functions are analyzed.
+// CHECK-C-NEXT: For analyzing C code you shouldn't pass the function parameter list, only the name of the function: -analyze-function=foobar
+
+// The user passed the '-analyzer-display-progress' option, we don't need to advocate it.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core \
+// RUN:   -analyze-function=missing_fn \
+// RUN:   -analyzer-display-progress -x c -Dbool=_Bool \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-DONT-ADVOCATE-DISPLAY-PROGRESS
+//
+// CHECK-DONT-ADVOCATE-DISPLAY-PROGRESS:     Every top-level function was skipped.
+// CHECK-DONT-ADVOCATE-DISPLAY-PROGRESS-NOT: Pass the -analyzer-display-progress
+
+// The user passed the '-analyze-function' option but that doesn't mach to any declaration.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core \
+// RUN:   -analyze-function='missing_fn()' -x c++ \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-ADVOCATE-DISPLAY-PROGRESS
+//
+// CHECK-ADVOCATE-DISPLAY-PROGRESS:      Every top-level function was skipped.
+// CHECK-ADVOCATE-DISPLAY-PROGRESS-NEXT: Pass the -analyzer-display-progress for tracking which functions are analyzed.
+// CHECK-ADVOCATE-DISPLAY-PROGRESS-NOT:  For analyzing
+
+// The user passed the '-analyze-function' option and that matches on a
+// declaration in C++ mode.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core \
+// RUN:   -analyze-function='fizzbuzz(int, _Bool)' -x c++ \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-EMPTY --allow-empty
+//
+// Expected empty standard output.
+// CHECK-EMPTY-NOT: Every top-level function was skipped.
+
+// The user passed the '-analyze-function' option and that matches on a
+// declaration in C mode.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core \
+// RUN:   -analyze-function='fizzbuzz' -x c -Dbool=_Bool \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-EMPTY2 --allow-empty
+//
+// Expected empty standard output.
+// CHECK-EMPTY2-NOT: Every top-level function was skipped.
+
+// Same as the previous but syntax mode only.
+// FIXME: This should have empty standard output.
+//
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-config ipa=none \
+// RUN:   -analyze-function='fizzbuzz(int, _Bool)' -x c++ \
+// RUN:   2>&1 %s | FileCheck %s -check-prefix=CHECK-EMPTY3 --allow-empty
+//
+// FIXME: This should have empty standard output.
+// CHECK-EMPTY3:      Every top-level function was skipped.
+// CHECK-EMPTY3-NEXT: Pass the -analyzer-display-progress for tracking which functions are analyzed.