While trying to use the C libclang bindings to parse some sources, I have found that preprocessor directives do not show up in the AST.
Following recommendations from this previous question, and calling clang_parseTranslationUnit with the CXTranslationUnit_DetailedPreprocessingRecord flag does not resolve the issue.

I have been able to reproduce the issue with the following demo code (not cleaning up objects is intentional), which is a simple driver that sources its compile arguments from a compile_commands.json database located in the same directory as the tool for the file passed in as argv[1].

#include <clang-c/Index.h>
#include <iostream>
#include <vector>

int main(int argc, char **argv) {
  CXIndex index = clang_createIndex(0, 0);
  CXCompilationDatabase db = clang_CompilationDatabase_fromDirectory(".", nullptr);
  CXCompileCommands cmds = clang_CompilationDatabase_getCompileCommands(db, argv[1]);
  CXCompileCommand cmd = clang_CompileCommands_getCommand(cmds, 0);

  std::vector<const char *> args;
  for (int i = 0; i < clang_CompileCommand_getNumArgs(cmd); ++i) {
    args.push_back(clang_CompileCommand_getArg(cmd, i));
  }

  CXTranslationUnit tu;
  clang_parseTranslationUnit2FullArgv(index, nullptr, args.data(), args.size(),
                                      nullptr, 0, CXTranslationUnit_DetailedPreprocessingRecord, &tu);
  clang_visitChildren(clang_getTranslationUnitCursor(tu), visitor, nullptr);
}

The visitor function is a function that prints out some basic information about any preprocessor directives it encounters.

CXChildVisitResult visitor(CXCursor cursor, CXCursor parent,
                           CXClientData client_data) {
  if (clang_Location_isFromMainFile(clang_getCursorLocation(cursor)) == 0)
    return CXChildVisit_Continue;

  CXCursorKind kind = clang_getCursorKind(cursor);
  if (kind >= CXCursor_FirstPreprocessing &&
      kind <= CXCursor_LastPreprocessing) {
    CXTranslationUnit tu = clang_Cursor_getTranslationUnit(cursor);
    CXFile file = clang_getFile(tu, nullptr);

    unsigned line, column;
    clang_getExpansionLocation(
        clang_getRangeStart(clang_getCursorExtent(cursor)), &file, &line,
        &column, nullptr);
    std::cout << clang_getCString(clang_getFileName(file)) << ":" << line << ":"
              << column << " ["
              << clang_getCString(clang_getCursorKindSpelling(kind)) << "]n";
  }
  return CXChildVisit_Recurse;
}

The issue is that the preprocessor directives do not show up in the AST, despite there not being other errors.
I have tried appending -Xclang -detailed-preprocessing-record to the compile arguments, as suggested in the linked question, which does not resolve the issue.
Any help would be appreciated.