From bba729af3ef803c35c082417f89a1ac89462e22b Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Fri, 14 Jan 2022 08:34:11 +0100
Subject: [PATCH] [clang-check] Adjust argument adjusters for clang-check to
 strip options blocking the static analyzer

Output generation options (like `-save-temps`) will make the analyzer not executed even `--analyze` option is provided in the driver arguments.
Besides, the original approach of adding `--analyze` option will not work when (more than one) `-fsyntax-only` options are provided in the driver arguments.

This patch fixes these two problems by using the syntax-only adjuster to remove output generation options and manually filter out redundant `-fsyntax-only` options.

In the new implementation, the adjusters added by `ClangTool` will not be removed but used as dependencies for clang-check adjusters for analyzer options.

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D116329
---
 .../clang-check-analyze-save-temps.cpp        | 19 +++++++
 clang/tools/clang-check/ClangCheck.cpp        | 50 +++++++++++--------
 2 files changed, 49 insertions(+), 20 deletions(-)
 create mode 100644 clang/test/Tooling/clang-check-analyze-save-temps.cpp

diff --git a/clang/test/Tooling/clang-check-analyze-save-temps.cpp b/clang/test/Tooling/clang-check-analyze-save-temps.cpp
new file mode 100644
index 000000000000..768f2580c2db
--- /dev/null
+++ b/clang/test/Tooling/clang-check-analyze-save-temps.cpp
@@ -0,0 +1,19 @@
+// Check whether output generation options (like -save-temps) will not affect
+// the execution of the analyzer.
+
+// RUN: clang-check -analyze %s -- -save-temps -c -Xclang -verify
+
+// Check whether redundant -fsyntax-only options will affect the execution of
+// the analyzer.
+
+// RUN: clang-check -analyze %s -- \
+// RUN:   -fsyntax-only -c -fsyntax-only -Xclang -verify 2>&1 | \
+// RUN:   FileCheck %s --allow-empty
+
+// CHECK-NOT: argument unused during compilation: '--analyze'
+
+void a(int *x) {
+  if (x) {
+  }
+  *x = 47; // expected-warning {{Dereference of null pointer}}
+}
diff --git a/clang/tools/clang-check/ClangCheck.cpp b/clang/tools/clang-check/ClangCheck.cpp
index 4d6ded029e2f..df9a87a54760 100644
--- a/clang/tools/clang-check/ClangCheck.cpp
+++ b/clang/tools/clang-check/ClangCheck.cpp
@@ -208,27 +208,37 @@ int main(int argc, const char **argv) {
   ClangTool Tool(OptionsParser.getCompilations(),
                  OptionsParser.getSourcePathList());
 
-  // Clear adjusters because -fsyntax-only is inserted by the default chain.
-  Tool.clearArgumentsAdjusters();
+  if (Analyze) {
+    // Set output path if is provided by user.
+    //
+    // As the original -o options have been removed by default via the
+    // strip-output adjuster, we only need to add the analyzer -o options here
+    // when it is provided by users.
+    if (!AnalyzerOutput.empty())
+      Tool.appendArgumentsAdjuster(
+          getInsertArgumentAdjuster(CommandLineArguments{"-o", AnalyzerOutput},
+                                    ArgumentInsertPosition::END));
 
-  // Reset output path if is provided by user.
-  Tool.appendArgumentsAdjuster(
-      Analyze ? [&](const CommandLineArguments &Args, StringRef File) {
-                  auto Ret = getClangStripOutputAdjuster()(Args, File);
-                  if (!AnalyzerOutput.empty()) {
-                    Ret.emplace_back("-o");
-                    Ret.emplace_back(AnalyzerOutput);
-                  }
-                  return Ret;
-                }
-              : getClangStripOutputAdjuster());
-
-  Tool.appendArgumentsAdjuster(getClangStripDependencyFileAdjuster());
-
-  // Running the analyzer requires --analyze. Other modes can work with the
-  // -fsyntax-only option.
-  Tool.appendArgumentsAdjuster(getInsertArgumentAdjuster(
-      Analyze ? "--analyze" : "-fsyntax-only", ArgumentInsertPosition::BEGIN));
+    // Running the analyzer requires --analyze. Other modes can work with the
+    // -fsyntax-only option.
+    //
+    // The syntax-only adjuster is installed by default.
+    // Good: It also strips options that trigger extra output, like -save-temps.
+    // Bad:  We don't want the -fsyntax-only when executing the static analyzer.
+    //
+    // To enable the static analyzer, we first strip all -fsyntax-only options
+    // and then add an --analyze option to the front.
+    Tool.appendArgumentsAdjuster(
+        [&](const CommandLineArguments &Args, StringRef /*unused*/) {
+          CommandLineArguments AdjustedArgs;
+          for (const std::string &Arg : Args)
+            if (Arg != "-fsyntax-only")
+              AdjustedArgs.emplace_back(Arg);
+          return AdjustedArgs;
+        });
+    Tool.appendArgumentsAdjuster(
+        getInsertArgumentAdjuster("--analyze", ArgumentInsertPosition::BEGIN));
+  }
 
   ClangCheckActionFactory CheckFactory;
   std::unique_ptr<FrontendActionFactory> FrontendFactory;