feat! Breaking API changes of NeCTI's LibCompiler and LibDebugger.

what:

- They've now become CompilerKit and DebuggerKit.
- Expanding XCoff for NeBoot PowerPC backend.

Signed-off-by: Amlal El Mahrouss <amlal@nekernel.org>

1 files changed, 672 insertions, 0 deletions

diff --git a/dev/CompilerKit/src/Linker/DynamicLinker64PEF.cc b/dev/CompilerKit/src/Linker/DynamicLinker64PEF.cc
new file mode 100644
index 0000000..3fde11b
--- /dev/null
+++ b/dev/CompilerKit/src/Linker/DynamicLinker64PEF.cc
@@ -0,0 +1,672 @@
+/* -------------------------------------------
+
+  Copyright (C) 2024-2025 Amlal El Mahrouss, all rights reserved
+
+  @file DynamicLinker64PEF.cc
+  @brief: C++ 64-Bit PEF Linker for NeKernel.org
+
+------------------------------------------- */
+
+/// @author EL Mahrouss Amlal (amlal@nekernel.org)
+/// @brief NeKernel.org 64-bit PEF Linker.
+/// Last Rev: Sat Apr 19 CET 2025
+/// @note Do not look up for anything with .code64/.data64/.zero64!
+/// It will be loaded when the program loader will start the image.
+
+
+#include <CompilerKit/Defines.h>
+#include <CompilerKit/ErrorID.h>
+#include <CompilerKit/CodeGen.h>
+#include <CompilerKit/PEF.h>
+#include <CompilerKit/UUID.h>
+#include <CompilerKit/Version.h>
+#include <CompilerKit/AE.h>
+#include <CompilerKit/utils/CompilerUtils.h>
+
+#define kLinkerVersionStr                                                           \
+  "NeKernel.org 64-Bit Linker (Preferred Executable Format) %s, (c) Amlal El Mahrouss " \
+  "2024-2025 "                                                                      \
+  "all rights reserved.\n"
+
+#define MemoryCopy(DST, SRC, SZ) memcpy(DST, SRC, SZ)
+#define StringCompare(DST, SRC) strcmp(DST, SRC)
+
+#define kPefNoCpu (0U)
+#define kPefNoSubCpu (0U)
+
+#define kLinkerDefaultOrigin kPefBaseOrigin
+#define kLinkerId (0x5046FF)
+#define kLinkerAbiContainer "__PEFContainer:ABI:"
+
+#define kPrintF printf
+#define kLinkerSplash() kConsoleOut << std::printf(kLinkerVersionStr, kDistVersion)
+
+/// @brief PEF stack size symbol.
+#define kLinkerStackSizeSymbol "__PEFSizeOfReserveStack"
+
+#define kConsoleOut        \
+  (std::cout << "\e[0;31m" \
+             << "ld64: "   \
+             << "\e[0;97m")
+
+enum {
+  kABITypeNull    = 0,
+  kABITypeStart   = 0x1010, /* The start of ABI list. */
+  kABITypeNE      = 0x5046, /* PF (NeKernel.org's PEF ABI) */
+  kABITypeInvalid = 0xFFFF,
+};
+
+static CompilerKit::STLString kOutput           = "a" kPefExt;
+static Int32                  kAbi              = kABITypeNE;
+static Int32                  kSubArch          = kPefNoSubCpu;
+static Int32                  kArch             = CompilerKit::kPefArchInvalid;
+static Bool                   kFatBinaryEnable  = false;
+static Bool                   kStartFound       = false;
+static Bool                   kDuplicateSymbols = false;
+
+/* ld64 is to be found, mld is to be found at runtime. */
+static const Char* kLdDefineSymbol = ":UndefinedSymbol:";
+static const Char* kLdDynamicSym   = ":RuntimeSymbol:";
+
+/* object code and list. */
+static std::vector<CompilerKit::STLString>    kObjectList;
+static std::vector<Detail::DynamicLinkerBlob> kObjectBytes;
+
+///	@brief NE 64-bit Linker.
+/// @note This linker is made for PEF executable, thus NE based OSes.
+LIBCOMPILER_MODULE(DynamicLinker64PEF) {
+  bool is_executable = true;
+
+  ::signal(SIGSEGV, Detail::drvi_crash_handler);
+
+  /**
+   * @brief parse flags and trigger options.
+   */
+  for (size_t linker_arg = 1; linker_arg < argc; ++linker_arg) {
+    if (StringCompare(argv[linker_arg], "-help") == 0) {
+      kLinkerSplash();
+
+      kConsoleOut << "-version: Show linker version.\n";
+      kConsoleOut << "-help: Show linker help.\n";
+      kConsoleOut << "-verbose: Enable linker trace.\n";
+      kConsoleOut << "-dylib: Output as a Dynamic PEF.\n";
+      kConsoleOut << "-fat: Output as a FAT PEF.\n";
+      kConsoleOut << "-32k: Output as a 32x0 PEF.\n";
+      kConsoleOut << "-64k: Output as a 64x0 PEF.\n";
+      kConsoleOut << "-amd64: Output as a AMD64 PEF.\n";
+      kConsoleOut << "-rv64: Output as a RISC-V PEF.\n";
+      kConsoleOut << "-power64: Output as a POWER PEF.\n";
+      kConsoleOut << "-arm64: Output as a ARM64 PEF.\n";
+      kConsoleOut << "-output: Select the output file name.\n";
+
+      return LIBCOMPILER_SUCCESS;
+    } else if (StringCompare(argv[linker_arg], "-version") == 0) {
+      kLinkerSplash();
+
+      return LIBCOMPILER_SUCCESS;
+    } else if (StringCompare(argv[linker_arg], "-fat") == 0) {
+      kFatBinaryEnable = true;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-64k") == 0) {
+      kArch = CompilerKit::kPefArch64000;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-amd64") == 0) {
+      kArch = CompilerKit::kPefArchAMD64;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-32k") == 0) {
+      kArch = CompilerKit::kPefArch32000;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-power64") == 0) {
+      kArch = CompilerKit::kPefArchPowerPC;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-riscv64") == 0) {
+      kArch = CompilerKit::kPefArchRISCV;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-arm64") == 0) {
+      kArch = CompilerKit::kPefArchARM64;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-verbose") == 0) {
+      kVerbose = true;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-dylib") == 0) {
+      if (kOutput.empty()) {
+        continue;
+      }
+
+      if (kOutput.find(kPefExt) != CompilerKit::STLString::npos)
+        kOutput.erase(kOutput.find(kPefExt), strlen(kPefExt));
+
+      kOutput += kPefDylibExt;
+
+      is_executable = false;
+
+      continue;
+    } else if (StringCompare(argv[linker_arg], "-output") == 0) {
+      if ((linker_arg + 1) > argc) continue;
+
+      kOutput = argv[linker_arg + 1];
+      ++linker_arg;
+
+      continue;
+    } else {
+      if (argv[linker_arg][0] == '-') {
+        kConsoleOut << "unknown flag: " << argv[linker_arg] << "\n";
+        return EXIT_FAILURE;
+      }
+
+      kObjectList.emplace_back(argv[linker_arg]);
+
+      continue;
+    }
+  }
+
+  if (kOutput.empty()) {
+    kConsoleOut << "no output filename set." << std::endl;
+    return LIBCOMPILER_EXEC_ERROR;
+  } else if (kObjectList.empty()) {
+    kConsoleOut << "no input files." << std::endl;
+    return LIBCOMPILER_EXEC_ERROR;
+  } else {
+    namespace FS = std::filesystem;
+
+    // check for existing files, if they don't throw an error.
+    for (auto& obj : kObjectList) {
+      if (!FS::exists(obj)) {
+        // if filesystem doesn't find file
+        //          -> throw error.
+        kConsoleOut << "no such file: " << obj << std::endl;
+        return LIBCOMPILER_EXEC_ERROR;
+      }
+    }
+  }
+
+  // PEF expects a valid target architecture when outputing a binary.
+  if (kArch == CompilerKit::kPefArchInvalid) {
+    kConsoleOut << "no target architecture set, can't continue." << std::endl;
+    return LIBCOMPILER_EXEC_ERROR;
+  }
+
+  CompilerKit::PEFContainer pef_container{};
+
+  int32_t archs = kArch;
+
+  pef_container.Count    = 0UL;
+  pef_container.Kind     = is_executable ? CompilerKit::kPefKindExec : CompilerKit::kPefKindDylib;
+  pef_container.SubCpu   = kSubArch;
+  pef_container.Linker   = kLinkerId;  // Amlal El Mahrouss Linker
+  pef_container.Abi      = kAbi;       // Multi-Processor UX ABI
+  pef_container.Magic[0] = kPefMagic[kFatBinaryEnable ? 2 : 0];
+  pef_container.Magic[1] = kPefMagic[1];
+  pef_container.Magic[2] = kPefMagic[kFatBinaryEnable ? 0 : 2];
+  pef_container.Magic[3] = kPefMagic[3];
+  pef_container.Version  = kPefVersion;
+
+  // specify the start address, can be 0x10000
+  pef_container.Start    = kLinkerDefaultOrigin;
+  pef_container.HdrSz    = sizeof(CompilerKit::PEFContainer);
+  pef_container.Checksum = 0UL;
+
+  std::ofstream output_fc(kOutput, std::ofstream::binary);
+
+  if (output_fc.bad()) {
+    if (kVerbose) {
+      kConsoleOut << "error: " << strerror(errno) << "\n";
+    }
+
+    return LIBCOMPILER_FILE_NOT_FOUND;
+  }
+
+  //! Read AE to convert as PEF.
+
+  std::vector<CompilerKit::PEFCommandHeader> command_headers;
+  CompilerKit::Utils::AEReadableProtocol     reader_protocol{};
+
+  for (const auto& objectFile : kObjectList) {
+    if (!std::filesystem::exists(objectFile)) continue;
+
+    CompilerKit::AEHeader hdr{};
+
+    reader_protocol._Fp = std::ifstream(objectFile, std::ifstream::binary);
+    reader_protocol._Fp >> hdr;
+
+    if (hdr.fMagic[0] == kAEMag0 && hdr.fMagic[1] == kAEMag1 &&
+        hdr.fSize == sizeof(CompilerKit::AEHeader)) {
+      if (hdr.fArch != kArch) {
+        if (kVerbose) kConsoleOut << "is this a FAT binary? : ";
+
+        if (!kFatBinaryEnable) {
+          if (kVerbose) kConsoleOut << "not a FAT binary.\n";
+
+          kConsoleOut << "object " << objectFile
+                      << " is a different kind of architecture and output isn't "
+                         "treated as a FAT binary."
+                      << std::endl;
+
+          return LIBCOMPILER_FAT_ERROR;
+        } else {
+          if (kVerbose) {
+            kConsoleOut << "Architecture matches what we expect.\n";
+          }
+        }
+      }
+
+      // append arch type to archs varaible.
+      archs |= hdr.fArch;
+      std::size_t cnt = hdr.fCount;
+
+      if (kVerbose) kConsoleOut << "header found, record count: " << cnt << "\n";
+
+      pef_container.Count = cnt;
+
+      char_type* raw_ae_records = new char_type[cnt * sizeof(CompilerKit::AERecordHeader)];
+
+      if (!raw_ae_records) {
+        if (kVerbose) kConsoleOut << "allocation failed for records of count: " << cnt << "\n";
+      }
+
+      std::memset(raw_ae_records, 0, cnt * sizeof(CompilerKit::AERecordHeader));
+
+      auto* ae_records = reader_protocol.Read(raw_ae_records, cnt);
+
+      size_t org = kLinkerDefaultOrigin;
+
+      for (size_t ae_record_index = 0; ae_record_index < cnt; ++ae_record_index) {
+        CompilerKit::PEFCommandHeader command_header{0};
+        std::size_t                   offset_of_obj = ae_records[ae_record_index].fOffset;
+
+        MemoryCopy(command_header.Name, ae_records[ae_record_index].fName, kPefNameLen);
+
+        CompilerKit::STLString cmd_hdr_name(command_header.Name);
+
+        // check this header if it's any valid.
+        if (cmd_hdr_name.find(kPefCode64) == CompilerKit::STLString::npos &&
+            cmd_hdr_name.find(kPefData64) == CompilerKit::STLString::npos &&
+            cmd_hdr_name.find(kPefZero64) == CompilerKit::STLString::npos) {
+          if (cmd_hdr_name.find(kPefStart) == CompilerKit::STLString::npos &&
+              *command_header.Name == 0) {
+            if (cmd_hdr_name.find(kLdDefineSymbol) != CompilerKit::STLString::npos) {
+              goto ld_mark_header;
+            } else {
+              continue;
+            }
+          }
+        }
+
+        if (cmd_hdr_name.find(kPefStart) != CompilerKit::STLString::npos &&
+            cmd_hdr_name.find(kPefCode64) != CompilerKit::STLString::npos) {
+          kStartFound = true;
+        }
+
+      ld_mark_header:
+        command_header.Offset    = offset_of_obj;
+        command_header.Kind      = ae_records[ae_record_index].fKind;
+        command_header.Size      = ae_records[ae_record_index].fSize;
+        command_header.Cpu       = hdr.fArch;
+        command_header.VMAddress = org;  /// TODO:
+        command_header.SubCpu    = hdr.fSubArch;
+
+        org += command_header.Size;
+
+        if (kVerbose) {
+          kConsoleOut << "Record: " << ae_records[ae_record_index].fName << " is marked.\n";
+
+          kConsoleOut << "Offset: " << command_header.Offset << "\n";
+        }
+
+        command_headers.emplace_back(command_header);
+      }
+
+      delete[] raw_ae_records;
+      raw_ae_records = nullptr;
+
+      std::vector<char> bytes;
+      bytes.resize(hdr.fCodeSize);
+
+      reader_protocol._Fp.seekg(std::streamsize(hdr.fStartCode));
+      reader_protocol._Fp.read(bytes.data(), std::streamsize(hdr.fCodeSize));
+
+      kObjectBytes.push_back({.mBlob = bytes, .mOffset = hdr.fStartCode});
+
+      // Blob was written, close fp.
+
+      reader_protocol._Fp.close();
+
+      continue;
+    }
+
+    kConsoleOut << "not an object container: " << objectFile << std::endl;
+
+    // don't continue, it is a fatal error.
+    return LIBCOMPILER_EXEC_ERROR;
+  }
+
+  pef_container.Cpu = archs;
+
+  output_fc << pef_container;
+
+  if (kVerbose) {
+    kConsoleOut << "wrote container to: " << output_fc.tellp() << ".\n";
+  }
+
+  output_fc.seekp(std::streamsize(pef_container.HdrSz));
+
+  std::vector<CompilerKit::STLString> not_found;
+  std::vector<CompilerKit::STLString> symbols;
+
+  // step 2: check for errors (multiple symbols, undefined ones)
+
+  for (auto& command_hdr : command_headers) {
+    // check if this symbol needs to be resolved.
+    if (CompilerKit::STLString(command_hdr.Name).find(kLdDefineSymbol) !=
+            CompilerKit::STLString::npos &&
+        CompilerKit::STLString(command_hdr.Name).find(kLdDynamicSym) ==
+            CompilerKit::STLString::npos) {
+      if (kVerbose) kConsoleOut << "Found undefined symbol: " << command_hdr.Name << "\n";
+
+      if (auto it = std::find(not_found.begin(), not_found.end(),
+                              CompilerKit::STLString(command_hdr.Name));
+          it == not_found.end()) {
+        not_found.emplace_back(command_hdr.Name);
+      }
+    }
+
+    symbols.emplace_back(command_hdr.Name);
+  }
+
+  // Now try to solve these symbols.
+
+  for (size_t not_found_idx = 0; not_found_idx < command_headers.size(); ++not_found_idx) {
+    if (const auto it = std::find(not_found.begin(), not_found.end(),
+                                  CompilerKit::STLString(command_headers[not_found_idx].Name));
+        it != not_found.end()) {
+      CompilerKit::STLString symbol_imp = *it;
+
+      if (symbol_imp.find(kLdDefineSymbol) == CompilerKit::STLString::npos) continue;
+
+      // erase the lookup prefix.
+      symbol_imp.erase(0, symbol_imp.find(kLdDefineSymbol) + strlen(kLdDefineSymbol));
+
+      // demangle everything.
+      while (symbol_imp.find('$') != CompilerKit::STLString::npos)
+        symbol_imp.erase(symbol_imp.find('$'), 1);
+
+      // the reason we do is because, this may not match the symbol, and we need
+      // to look for other matching symbols.
+      for (auto& command_hdr : command_headers) {
+        if (CompilerKit::STLString(command_hdr.Name).find(symbol_imp) !=
+                CompilerKit::STLString::npos &&
+            CompilerKit::STLString(command_hdr.Name).find(kLdDefineSymbol) ==
+                CompilerKit::STLString::npos) {
+          CompilerKit::STLString undefined_symbol = command_hdr.Name;
+          auto result_of_sym = undefined_symbol.substr(undefined_symbol.find(symbol_imp));
+
+          for (int i = 0; result_of_sym[i] != 0; ++i) {
+            if (result_of_sym[i] != symbol_imp[i]) goto ld_continue_search;
+          }
+
+          not_found.erase(it);
+
+          if (kVerbose) kConsoleOut << "Found symbol: " << command_hdr.Name << "\n";
+
+          break;
+        }
+      }
+
+    ld_continue_search:
+      continue;
+    }
+  }
+
+  // step 3: check for errors (recheck if we have those symbols.)
+
+  if (!kStartFound && is_executable) {
+    if (kVerbose)
+      kConsoleOut << "Undefined entrypoint: " << kPefStart
+                  << ", you may have forget to link "
+                     "against the C++ runtime library.\n";
+
+    kConsoleOut << "Undefined entrypoint " << kPefStart << " for executable: " << kOutput << "\n";
+  }
+
+  // step 4: write all PEF commands.
+
+  CompilerKit::PEFCommandHeader date_cmd_hdr{};
+
+  time_t timestamp = time(nullptr);
+
+  CompilerKit::STLString timeStampStr = "Container:BuildEpoch:";
+  timeStampStr += std::to_string(timestamp);
+
+  strncpy(date_cmd_hdr.Name, timeStampStr.c_str(), timeStampStr.size());
+
+  date_cmd_hdr.Flags  = 0;
+  date_cmd_hdr.Kind   = CompilerKit::kPefZero;
+  date_cmd_hdr.Offset = output_fc.tellp();
+  date_cmd_hdr.Size   = timeStampStr.size();
+
+  command_headers.push_back(date_cmd_hdr);
+
+  CompilerKit::PEFCommandHeader abi_cmd_hdr{};
+
+  CompilerKit::STLString abi = kLinkerAbiContainer;
+
+  switch (kArch) {
+    case CompilerKit::kPefArchAMD64: {
+      abi += "MSFT";
+      break;
+    }
+    case CompilerKit::kPefArchPowerPC: {
+      abi += "SYSV";
+      break;
+    }
+    case CompilerKit::kPefArch32000:
+    case CompilerKit::kPefArch64000: {
+      abi += "_NEP";
+      break;
+    }
+    default: {
+      abi += "_IDK";
+      break;
+    }
+  }
+
+  MemoryCopy(abi_cmd_hdr.Name, abi.c_str(), abi.size());
+
+  abi_cmd_hdr.Size   = abi.size();
+  abi_cmd_hdr.Offset = output_fc.tellp();
+  abi_cmd_hdr.Flags  = 0;
+  abi_cmd_hdr.Kind   = CompilerKit::kPefLinkerID;
+
+  command_headers.push_back(abi_cmd_hdr);
+
+  CompilerKit::PEFCommandHeader stack_cmd_hdr{0};
+
+  stack_cmd_hdr.Cpu    = kArch;
+  stack_cmd_hdr.Flags  = 0;
+  stack_cmd_hdr.Size   = sizeof(uintptr_t);
+  stack_cmd_hdr.Offset = 0;
+
+  MemoryCopy(stack_cmd_hdr.Name, kLinkerStackSizeSymbol, strlen(kLinkerStackSizeSymbol));
+
+  command_headers.push_back(stack_cmd_hdr);
+
+  CompilerKit::PEFCommandHeader uuid_cmd_hdr{};
+
+  std::random_device rd;
+
+  auto seedData = std::array<int, std::mt19937::state_size>{};
+  std::generate(std::begin(seedData), std::end(seedData), std::ref(rd));
+  std::seed_seq seq(std::begin(seedData), std::end(seedData));
+  std::mt19937  generator(seq);
+
+  auto        gen     = uuids::uuid_random_generator{generator};
+  uuids::uuid id      = gen();
+  auto        uuidStr = uuids::to_string(id);
+
+  MemoryCopy(uuid_cmd_hdr.Name, "Container:GUID:4:", strlen("Container:GUID:4:"));
+  MemoryCopy(uuid_cmd_hdr.Name + strlen("Container:GUID:4:"), uuidStr.c_str(), uuidStr.size());
+
+  uuid_cmd_hdr.Size   = strlen(uuid_cmd_hdr.Name);
+  uuid_cmd_hdr.Offset = output_fc.tellp();
+  uuid_cmd_hdr.Flags  = CompilerKit::kPefLinkerID;
+  uuid_cmd_hdr.Kind   = CompilerKit::kPefZero;
+
+  command_headers.push_back(uuid_cmd_hdr);
+
+  // prepare a symbol vector.
+  std::vector<CompilerKit::STLString> undef_symbols;
+  std::vector<CompilerKit::STLString> dupl_symbols;
+  std::vector<CompilerKit::STLString> resolve_symbols;
+
+  constexpr Int32 kPaddingOffset = 16;
+
+  size_t previous_offset =
+      (command_headers.size() * sizeof(CompilerKit::PEFCommandHeader)) + kPaddingOffset;
+
+  CompilerKit::PEFCommandHeader end_exec_hdr;
+
+  end_exec_hdr.Offset = output_fc.tellp();
+  end_exec_hdr.Flags  = CompilerKit::kPefLinkerID;
+  end_exec_hdr.Kind   = CompilerKit::kPefZero;
+
+  MemoryCopy(end_exec_hdr.Name, "Container:Exec:END", strlen("Container:Exec:END"));
+
+  end_exec_hdr.Size = strlen(end_exec_hdr.Name);
+
+  command_headers.push_back(end_exec_hdr);
+
+  // Finally write down the command headers.
+  // And check for any duplications
+  for (size_t commandHeaderIndex = 0UL; commandHeaderIndex < command_headers.size();
+       ++commandHeaderIndex) {
+    if (CompilerKit::STLString(command_headers[commandHeaderIndex].Name).find(kLdDefineSymbol) !=
+            CompilerKit::STLString::npos &&
+        CompilerKit::STLString(command_headers[commandHeaderIndex].Name).find(kLdDynamicSym) ==
+            CompilerKit::STLString::npos) {
+      // ignore :UndefinedSymbol: headers, they do not contain code.
+      continue;
+    }
+
+    CompilerKit::STLString symbol_name = command_headers[commandHeaderIndex].Name;
+
+    if (!symbol_name.empty()) {
+      undef_symbols.emplace_back(symbol_name);
+    }
+
+    command_headers[commandHeaderIndex].Offset += previous_offset;
+    previous_offset += command_headers[commandHeaderIndex].Size;
+
+    CompilerKit::STLString name = command_headers[commandHeaderIndex].Name;
+
+    /// so this is valid when we get to the entrypoint.
+    /// it is always a code64 container. And should equal to kPefStart as well.
+    /// this chunk of code updates the pef_container.Start with the updated offset.
+    if (name.find(kPefStart) != CompilerKit::STLString::npos &&
+        name.find(kPefCode64) != CompilerKit::STLString::npos) {
+      pef_container.Start = command_headers[commandHeaderIndex].Offset;
+      auto tellCurPos     = output_fc.tellp();
+
+      output_fc.seekp(0);
+      output_fc << pef_container;
+
+      output_fc.seekp(tellCurPos);
+    }
+
+    if (kVerbose) {
+      kConsoleOut << "Command name: " << name << "\n";
+      kConsoleOut << "VMAddress of command content: " << command_headers[commandHeaderIndex].Offset
+                  << "\n";
+    }
+
+    output_fc << command_headers[commandHeaderIndex];
+
+    for (size_t sub_command_header_index = 0UL; sub_command_header_index < command_headers.size();
+         ++sub_command_header_index) {
+      if (sub_command_header_index == commandHeaderIndex) continue;
+
+      if (CompilerKit::STLString(command_headers[sub_command_header_index].Name)
+                  .find(kLdDefineSymbol) != CompilerKit::STLString::npos &&
+          CompilerKit::STLString(command_headers[sub_command_header_index].Name)
+                  .find(kLdDynamicSym) == CompilerKit::STLString::npos) {
+        if (kVerbose) {
+          kConsoleOut << "Ignoring :UndefinedSymbol: headers...\n";
+        }
+
+        // ignore :UndefinedSymbol: headers, they do not contain code.
+        continue;
+      }
+
+      auto& command_hdr = command_headers[sub_command_header_index];
+
+      if (command_hdr.Name == CompilerKit::STLString(command_headers[commandHeaderIndex].Name)) {
+        if (std::find(dupl_symbols.cbegin(), dupl_symbols.cend(), command_hdr.Name) ==
+            dupl_symbols.cend()) {
+          dupl_symbols.emplace_back(command_hdr.Name);
+        }
+
+        if (kVerbose) kConsoleOut << "Found duplicate symbols of: " << command_hdr.Name << "\n";
+
+        kDuplicateSymbols = true;
+      }
+    }
+  }
+
+  if (!dupl_symbols.empty()) {
+    for (auto& symbol : dupl_symbols) {
+      kConsoleOut << "Multiple symbols of: " << symbol << " detected, cannot continue.\n";
+    }
+
+    return LIBCOMPILER_EXEC_ERROR;
+  }
+
+  // step 2.5: write program bytes.
+
+  for (auto& struct_of_blob : kObjectBytes) {
+    output_fc.write(struct_of_blob.mBlob.data(), struct_of_blob.mBlob.size());
+  }
+
+  if (kVerbose) {
+    kConsoleOut << "Wrote contents of: " << kOutput << "\n";
+  }
+
+  // step 3: check if we have those symbols
+
+  std::vector<CompilerKit::STLString> unreferenced_symbols;
+
+  for (auto& command_hdr : command_headers) {
+    if (auto it =
+            std::find(not_found.begin(), not_found.end(), CompilerKit::STLString(command_hdr.Name));
+        it != not_found.end()) {
+      unreferenced_symbols.emplace_back(command_hdr.Name);
+    }
+  }
+
+  if (!unreferenced_symbols.empty()) {
+    for (auto& unreferenced_symbol : unreferenced_symbols) {
+      kConsoleOut << "Undefined symbol " << unreferenced_symbol << "\n";
+    }
+
+    return LIBCOMPILER_EXEC_ERROR;
+  }
+
+  if ((!kStartFound || kDuplicateSymbols) &&
+      (std::filesystem::exists(kOutput) || !unreferenced_symbols.empty())) {
+    if (kVerbose) {
+      kConsoleOut << "File: " << kOutput << ", is corrupt, removing file...\n";
+    }
+
+    return LIBCOMPILER_EXEC_ERROR;
+  }
+
+  return LIBCOMPILER_SUCCESS;
+}
+
+// Last rev 13-1-24