[driver] Make --version show if assertions, etc. are enabled (#87585)

It's useful to have some significant build options visible in the
version when investigating problems with a specific compiler artifact.
This makes it easy to see if assertions, expensive checks, sanitizers,
etc. are enabled when checking a compiler version.

Example config line output:
Build configuration: +unoptimized, +assertions, +asan, +ubsan

clang/lib/Driver/Driver.cpp

@@ -2003,6 +2003,12 @@ void Driver::PrintVersion(const Compilation &C, raw_ostream &OS) const {
   // Print out the install directory.
   OS << "InstalledDir: " << Dir << '\n';
 
+  // Print the build config if it's non-default.
+  // Intended to help LLVM developers understand the configs of compilers
+  // they're investigating.
+  if (!llvm::cl::getCompilerBuildConfig().empty())
+    llvm::cl::printBuildConfig(OS);
+
   // If configuration files were used, print their paths.
   for (auto ConfigFile : ConfigFiles)
     OS << "Configuration file: " << ConfigFile << '\n';

clang/test/Driver/version-build-config.test

@@ -0,0 +1,6 @@
+# REQUIRES: asserts
+# RUN: %clang --version 2>&1 | FileCheck %s
+
+# CHECK: clang version
+# When assertions are enabled, we should have a build configuration line that reflects that
+# CHECK: Build config: {{.*}}+assertions

llvm/CMakeLists.txt

@@ -799,6 +799,9 @@ option (LLVM_BUILD_EXTERNAL_COMPILER_RT
 option (LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
   "Show target and host info when tools are invoked with --version." ON)
 
+option(LLVM_VERSION_PRINTER_SHOW_BUILD_CONFIG
+  "Show the optional build config flags when tools are invoked with --version." ON)
+
 # You can configure which libraries from LLVM you want to include in the
 # shared library by setting LLVM_DYLIB_COMPONENTS to a semi-colon delimited
 # list of LLVM components. All component names handled by llvm-config are valid.

llvm/include/llvm/Config/config.h.cmake

@@ -290,6 +290,9 @@
 /* Whether tools show host and target info when invoked with --version */
 #cmakedefine01 LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
 
+/* Whether tools show optional build config flags when invoked with --version */
+#cmakedefine01 LLVM_VERSION_PRINTER_SHOW_BUILD_CONFIG
+
 /* Define if libxml2 is supported on this platform. */
 #cmakedefine LLVM_ENABLE_LIBXML2 ${LLVM_ENABLE_LIBXML2}
 

llvm/include/llvm/Support/CommandLine.h

@@ -2002,6 +2002,16 @@ void PrintVersionMessage();
 /// \param Categorized if true print options in categories
 void PrintHelpMessage(bool Hidden = false, bool Categorized = false);
 
+/// An array of optional enabled settings in the LLVM build configuration,
+/// which may be of interest to compiler developers. For example, includes
+/// "+assertions" if assertions are enabled. Used by printBuildConfig.
+ArrayRef<StringRef> getCompilerBuildConfig();
+
+/// Prints the compiler build configuration.
+/// Designed for compiler developers, not compiler end-users.
+/// Intended to be used in --version output when enabled.
+void printBuildConfig(raw_ostream &OS);
+
 //===----------------------------------------------------------------------===//
 // Public interface for accessing registered options.
 //

llvm/lib/Support/CommandLine.cpp

@@ -2734,6 +2734,52 @@ void cl::PrintHelpMessage(bool Hidden, bool Categorized) {
     CommonOptions->CategorizedHiddenPrinter.printHelp();
 }
 
+ArrayRef<StringRef> cl::getCompilerBuildConfig() {
+  static const StringRef Config[] = {
+      // Placeholder to ensure the array always has elements, since it's an
+      // error to have a zero-sized array. Slice this off before returning.
+      "",
+  // Actual compiler build config feature list:
+#if LLVM_IS_DEBUG_BUILD
+      "+unoptimized",
+#endif
+#ifndef NDEBUG
+      "+assertions",
+#endif
+#ifdef EXPENSIVE_CHECKS
+      "+expensive-checks",
+#endif
+#if __has_feature(address_sanitizer)
+      "+asan",
+#endif
+#if __has_feature(dataflow_sanitizer)
+      "+dfsan",
+#endif
+#if __has_feature(hwaddress_sanitizer)
+      "+hwasan",
+#endif
+#if __has_feature(memory_sanitizer)
+      "+msan",
+#endif
+#if __has_feature(thread_sanitizer)
+      "+tsan",
+#endif
+#if __has_feature(undefined_behavior_sanitizer)
+      "+ubsan",
+#endif
+  };
+  return ArrayRef(Config).drop_front(1);
+}
+
+// Utility function for printing the build config.
+void cl::printBuildConfig(raw_ostream &OS) {
+#if LLVM_VERSION_PRINTER_SHOW_BUILD_CONFIG
+  OS << "Build config: ";
+  llvm::interleaveComma(cl::getCompilerBuildConfig(), OS);
+  OS << '\n';
+#endif
+}
+
 /// Utility function for printing version number.
 void cl::PrintVersionMessage() {
   CommonOptions->VersionPrinterInstance.print(CommonOptions->ExtraVersionPrinters);