[clang-tidy] Do not crash when an empty directory is used in the comp… (llvm#156873)

…ilation database

Currently a hard crash encourages people to report a bug upstream, but
this is not really a bug. Instead, print an error and use a reasonable
default (the current working directory).

Fixes llvm#57264

Co-authored-by: Carlos Gálvez <[email protected]>

Author: carlosgalvezp

clang-tools-extra/docs/ReleaseNotes.rst

@@ -126,6 +126,10 @@ Improvements to clang-tidy
 - Improved :program:`clang-tidy` option `-quiet` by suppressing diagnostic
   count messages.
 
+- Improved :program:`clang-tidy` by not crashing when an empty `directory`
+  field is used in a compilation database; the current working directory
+  will be used instead, and an error message will be printed.
+
 New checks
 ^^^^^^^^^^
 

clang-tools-extra/test/clang-tidy/infrastructure/Inputs/invalid-database/compile_commands.json

@@ -0,0 +1,5 @@
+[{
+    "directory":"/invalid/",
+    "file":"/tmp/",
+    "arguments": []
+}]

clang-tools-extra/test/clang-tidy/infrastructure/empty-database.cpp

@@ -1,5 +1,5 @@
 // UNSUPPORTED: system-windows
 
-// RUN: not --crash clang-tidy -p %S/Inputs/empty-database %s 2>&1 | FileCheck %s
+// RUN: clang-tidy -p %S/Inputs/empty-database %s 2>&1 | FileCheck %s
 
-// CHECK: LLVM ERROR: Cannot chdir into ""!
+// CHECK: 'directory' field of compilation database is empty; using the current working directory instead.

clang-tools-extra/test/clang-tidy/infrastructure/invalid-database.cpp

@@ -0,0 +1,5 @@
+// UNSUPPORTED: system-windows
+
+// RUN: not --crash clang-tidy -p %S/Inputs/invalid-database %s 2>&1 | FileCheck %s
+
+// CHECK: LLVM ERROR: Cannot chdir into "/invalid/"!

clang/lib/Tooling/Tooling.cpp

@@ -574,22 +574,30 @@ int ClangTool::run(ToolAction *Action) {
       continue;
     }
     for (CompileCommand &CompileCommand : CompileCommandsForFile) {
+      // If the 'directory' field of the compilation database is empty, display
+      // an error and use the working directory instead.
+      StringRef Directory = CompileCommand.Directory;
+      if (Directory.empty()) {
+        llvm::errs() << "'directory' field of compilation database is empty; "
+                        "using the current working directory instead.\n";
+        Directory = InitialWorkingDir;
+      }
+
       // FIXME: chdir is thread hostile; on the other hand, creating the same
       // behavior as chdir is complex: chdir resolves the path once, thus
       // guaranteeing that all subsequent relative path operations work
       // on the same path the original chdir resulted in. This makes a
       // difference for example on network filesystems, where symlinks might be
       // switched during runtime of the tool. Fixing this depends on having a
       // file system abstraction that allows openat() style interactions.
-      if (OverlayFileSystem->setCurrentWorkingDirectory(
-              CompileCommand.Directory))
-        llvm::report_fatal_error("Cannot chdir into \"" +
-                                 Twine(CompileCommand.Directory) + "\"!");
+      if (OverlayFileSystem->setCurrentWorkingDirectory(Directory))
+        llvm::report_fatal_error("Cannot chdir into \"" + Twine(Directory) +
+                                 "\"!");
 
       // Now fill the in-memory VFS with the relative file mappings so it will
       // have the correct relative paths. We never remove mappings but that
       // should be fine.
-      if (SeenWorkingDirectories.insert(CompileCommand.Directory).second)
+      if (SeenWorkingDirectories.insert(Directory).second)
         for (const auto &MappedFile : MappedFileContents)
           if (!llvm::sys::path::is_absolute(MappedFile.first))
             InMemoryFileSystem->addFile(