Merge commit 'd411a950d867' from apple/stable/20200714 into swift/release/5.4

Author: Teemperor

lldb/source/Plugins/ExpressionParser/Clang/CppModuleConfiguration.cpp

@@ -55,9 +55,38 @@ bool CppModuleConfiguration::analyzeFile(const FileSpec &f) {
   return true;
 }
 
+/// Utility function for just appending two paths.
+static std::string MakePath(llvm::StringRef lhs, llvm::StringRef rhs) {
+  llvm::SmallString<256> result(lhs);
+  llvm::sys::path::append(result, rhs);
+  return std::string(result);
+}
+
 bool CppModuleConfiguration::hasValidConfig() {
-  // We all these include directories to have a valid usable configuration.
-  return m_c_inc.Valid() && m_std_inc.Valid();
+  // We need to have a C and C++ include dir for a valid configuration.
+  if (!m_c_inc.Valid() || !m_std_inc.Valid())
+    return false;
+
+  // Do some basic sanity checks on the directories that we don't activate
+  // the module when it's clear that it's not usable.
+  const std::vector<std::string> files_to_check = {
+      // * Check that the C library contains at least one random C standard
+      //   library header.
+      MakePath(m_c_inc.Get(), "stdio.h"),
+      // * Without a libc++ modulemap file we can't have a 'std' module that
+      //   could be imported.
+      MakePath(m_std_inc.Get(), "module.modulemap"),
+      // * Check for a random libc++ header (vector in this case) that has to
+      //   exist in a working libc++ setup.
+      MakePath(m_std_inc.Get(), "vector"),
+  };
+
+  for (llvm::StringRef file_to_check : files_to_check) {
+    if (!FileSystem::Instance().Exists(file_to_check))
+      return false;
+  }
+
+  return true;
 }
 
 CppModuleConfiguration::CppModuleConfiguration(
@@ -76,7 +105,8 @@ CppModuleConfiguration::CppModuleConfiguration(
     m_resource_inc = std::string(resource_dir.str());
 
     // This order matches the way Clang orders these directories.
-    m_include_dirs = {m_std_inc.Get(), m_resource_inc, m_c_inc.Get()};
+    m_include_dirs = {m_std_inc.Get().str(), m_resource_inc,
+                      m_c_inc.Get().str()};
     m_imported_modules = {"std"};
   }
 }

lldb/source/Plugins/ExpressionParser/Clang/CppModuleConfiguration.h

@@ -32,7 +32,7 @@ class CppModuleConfiguration {
     /// the path was already set.
     LLVM_NODISCARD bool TrySet(llvm::StringRef path);
     /// Return the path if there is one.
-    std::string Get() const {
+    llvm::StringRef Get() const {
       assert(m_valid && "Called Get() on an invalid SetOncePath?");
       return m_path;
     }
@@ -57,9 +57,6 @@ class CppModuleConfiguration {
 
 public:
   /// Creates a configuration by analyzing the given list of used source files.
-  ///
-  /// Currently only looks at the used paths and doesn't actually access the
-  /// files on the disk.
   explicit CppModuleConfiguration(const FileSpecList &support_files);
   /// Creates an empty and invalid configuration.
   CppModuleConfiguration() {}

lldb/test/API/commands/expression/import-std-module/empty-module/root/usr/include/c++/v1/algorithm

@@ -2,7 +2,7 @@
 // library module so the actual contents of the module are missing.
 #ifdef ENABLE_STD_CONTENT
 
-#include "libc_header.h"
+#include "stdio.h"
 
 namespace std {
   inline namespace __1 {

lldb/test/API/commands/expression/import-std-module/empty-module/root/usr/include/c++/v1/vector

@@ -1,4 +1,4 @@
-#include "libc_header.h"
+#include "stdio.h"
 
 namespace std {
   inline namespace __1 {

lldb/test/API/commands/expression/import-std-module/empty-module/root/usr/include/libc_header.h renamed to lldb/test/API/commands/expression/import-std-module/empty-module/root/usr/include/stdio.h

@@ -0,0 +1,10 @@
+# We don't have any standard include directories, so we can't
+# parse the test_common.h header we usually inject as it includes
+# system headers.
+NO_TEST_COMMON_H := 1
+
+# Take the libc++ from the build directory (which will be later deleted).
+CXXFLAGS_EXTRAS = -I $(BUILDDIR)/root/usr/include/c++/v1/ -I $(BUILDDIR)/root/usr/include/ -nostdinc -nostdinc++
+CXX_SOURCES := main.cpp
+
+include Makefile.rules

lldb/test/API/commands/expression/import-std-module/forward_decl_from_module/root/usr/include/c++/v1/vector

@@ -0,0 +1,60 @@
+"""
+Check that missing module source files are correctly handled by LLDB.
+"""
+
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+import os
+import shutil
+
+
+class TestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    # We only emulate a fake libc++ in this test and don't use the real libc++,
+    # but we still add the libc++ category so that this test is only run in
+    # test configurations where libc++ is actually supposed to be tested.
+    @add_test_categories(["libc++"])
+    @skipIf(compiler=no_match("clang"))
+    def test(self):
+        # The path to our temporary target root that contains the temporary
+        # module sources.
+        target_sysroot = self.getBuildArtifact("root")
+
+        # Copy the sources to the root.
+        shutil.copytree(self.getSourcePath("root"), target_sysroot)
+        # Build the binary with the copied sources.
+        self.build()
+        # Delete the copied sources so that they are now unavailable.
+        shutil.rmtree(target_sysroot)
+
+        # Set the sysroot where our dummy libc++ used to exist. Just to make
+        # sure we don't find some existing headers on the system that could
+        # XPASS this test.
+        self.runCmd("platform select --sysroot '" + target_sysroot + "' host")
+
+        lldbutil.run_to_source_breakpoint(self,
+                                          "// Set break point at this line.",
+                                          lldb.SBFileSpec("main.cpp"))
+
+        # Import the std C++ module and run an expression.
+        # As we deleted the sources, LLDB should refuse the load the module
+        # and just print the normal error we get from the expression.
+        self.runCmd("settings set target.import-std-module true")
+        self.expect("expr v.unknown_identifier", error=True,
+                    substrs=["no member named 'unknown_identifier'"])
+        # Check that there is no confusing error about failing to build the
+        # module.
+        self.expect("expr v.unknown_identifier", error=True, matching=False,
+                    substrs=["could not build module 'std'"])
+
+        # Test the fallback mode. It should also just print the normal
+        # error but not mention a failed module build.
+        self.runCmd("settings set target.import-std-module fallback")
+
+        self.expect("expr v.unknown_identifier", error=True,
+                     substrs=["no member named 'unknown_identifier'"])
+        self.expect("expr v.unknown_identifier", error=True, matching=False,
+                    substrs=["could not build module 'std'"])

lldb/test/API/commands/expression/import-std-module/forward_decl_from_module/root/usr/include/libc_header.h renamed to lldb/test/API/commands/expression/import-std-module/forward_decl_from_module/root/usr/include/stdio.h

@@ -0,0 +1,8 @@
+#include <vector>
+
+int main(int argc, char **argv) {
+  // Makes sure we have the mock libc headers in the debug information.
+  libc_struct s;
+  std::vector<int> v;
+  return 0; // Set break point at this line.
+}