Merge topic 'aix-xcoff-edit'

e017ba046c AIX: Enable XCOFF editing to replace RPATH on installation
56fc4a325f cmXCOFF: Add helper to parse and edit the XCOFF binary format
ddaaee907d CMakeDetermineCompilerId: Recognize XCOFF executable format
69e1d95a8a Tests: Add sample XCOFF binaries
f79d991dfd Tests: Convert CMake.ELF to RunCMake.file-RPATH ELF case
d8f3e68ca9 Ninja Multi-Config: Enable relink diagnostic message
cdcfe3eb99 Rename CMAKE_USE_MACH_PARSER to CMake_USE_MACH_PARSER
b6071c93f5 Rename CMAKE_USE_ELF_PARSER to CMake_USE_ELF_PARSER

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !5769

11 files changed, 588 insertions, 37 deletions

diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index b3d8369..6adc9cf 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -19,7 +19,7 @@ else()
   CHECK_INCLUDE_FILE("elf.h" HAVE_ELF_H)
 endif()
 if(HAVE_ELF_H)
-  set(CMAKE_USE_ELF_PARSER 1)
+  set(CMake_USE_ELF_PARSER 1)
 elseif(HAIKU)
   # On Haiku, we need to include elf32.h from the private headers
   set(CMake_HAIKU_INCLUDE_DIRS
@@ -32,13 +32,13 @@ elseif(HAIKU)
   unset(CMAKE_REQUIRED_INCLUDES)
 
   if(HAVE_ELF32_H)
-    set(CMAKE_USE_ELF_PARSER 1)
+    set(CMake_USE_ELF_PARSER 1)
   else()
     unset(CMake_HAIKU_INCLUDE_DIRS)
-    set(CMAKE_USE_ELF_PARSER)
+    set(CMake_USE_ELF_PARSER)
   endif()
 else()
-  set(CMAKE_USE_ELF_PARSER)
+  set(CMake_USE_ELF_PARSER)
 endif()
 
 if(NOT CMake_DEFAULT_RECURSION_LIMIT)
@@ -54,7 +54,11 @@ if(NOT CMake_DEFAULT_RECURSION_LIMIT)
 endif()
 
 if(APPLE)
-  set(CMAKE_USE_MACH_PARSER 1)
+  set(CMake_USE_MACH_PARSER 1)
+endif()
+
+if(CMAKE_SYSTEM_NAME STREQUAL "AIX")
+  set(CMake_USE_XCOFF_PARSER 1)
 endif()
 
 set(EXECUTABLE_OUTPUT_PATH ${CMake_BIN_DIR})
@@ -108,15 +112,20 @@ include_directories(
   )
 
 # Check if we can build the ELF parser.
-if(CMAKE_USE_ELF_PARSER)
+if(CMake_USE_ELF_PARSER)
   set(ELF_SRCS cmELF.h cmELF.cxx)
 endif()
 
 # Check if we can build the Mach-O parser.
-if(CMAKE_USE_MACH_PARSER)
+if(CMake_USE_MACH_PARSER)
   set(MACH_SRCS cmMachO.h cmMachO.cxx)
 endif()
 
+# Check if we can build the XCOFF parser.
+if(CMake_USE_XCOFF_PARSER)
+  set(XCOFF_SRCS cmXCOFF.h cmXCOFF.cxx)
+endif()
+
 #
 # Sources for CMakeLib
 #
@@ -465,6 +474,7 @@ set(SRCS
   cmWorkerPool.h
   cmWorkingDirectory.cxx
   cmWorkingDirectory.h
+  ${XCOFF_SRCS}
   cmXMLParser.cxx
   cmXMLParser.h
   cmXMLSafe.cxx
diff --git a/Source/cmConfigure.cmake.h.in b/Source/cmConfigure.cmake.h.in
index cf32b05..aeca6b4 100644
--- a/Source/cmConfigure.cmake.h.in
+++ b/Source/cmConfigure.cmake.h.in
@@ -16,8 +16,9 @@
 
 #cmakedefine HAVE_ENVIRON_NOT_REQUIRE_PROTOTYPE
 #cmakedefine HAVE_UNSETENV
-#cmakedefine CMAKE_USE_ELF_PARSER
-#cmakedefine CMAKE_USE_MACH_PARSER
+#cmakedefine CMake_USE_ELF_PARSER
+#cmakedefine CMake_USE_MACH_PARSER
+#cmakedefine CMake_USE_XCOFF_PARSER
 #define CMake_DEFAULT_RECURSION_LIMIT @CMake_DEFAULT_RECURSION_LIMIT@
 #define CMAKE_BIN_DIR "/@CMAKE_BIN_DIR@"
 #define CMAKE_DATA_DIR "/@CMAKE_DATA_DIR@"
diff --git a/Source/cmELF.h b/Source/cmELF.h
index 99eb4f4..c479e2b 100644
--- a/Source/cmELF.h
+++ b/Source/cmELF.h
@@ -10,8 +10,8 @@
 #include <utility>
 #include <vector>
 
-#if !defined(CMAKE_USE_ELF_PARSER)
-#  error "This file may be included only if CMAKE_USE_ELF_PARSER is enabled."
+#if !defined(CMake_USE_ELF_PARSER)
+#  error "This file may be included only if CMake_USE_ELF_PARSER is enabled."
 #endif
 
 class cmELFInternal;
diff --git a/Source/cmFileCommand.cxx b/Source/cmFileCommand.cxx
index 031e0d7..f674833 100644
--- a/Source/cmFileCommand.cxx
+++ b/Source/cmFileCommand.cxx
@@ -64,7 +64,7 @@
 #  include "cmFileLockResult.h"
 #endif
 
-#if defined(CMAKE_USE_ELF_PARSER)
+#if defined(CMake_USE_ELF_PARSER)
 #  include "cmELF.h"
 #endif
 
@@ -1198,7 +1198,7 @@ bool HandleReadElfCommand(std::vector<std::string> const& args,
     return false;
   }
 
-#if defined(CMAKE_USE_ELF_PARSER)
+#if defined(CMake_USE_ELF_PARSER)
   cmELF elf(fileNameArg.c_str());
 
   if (!arguments.RPath.empty()) {
diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index aaefe9c..9235faa 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -2003,17 +2003,16 @@ bool cmGeneratorTarget::NeedRelinkBeforeInstall(
   // this target must be relinked.
   bool have_rpath =
     this->HaveBuildTreeRPATH(config) || this->HaveInstallTreeRPATH(config);
-  bool is_ninja =
-    this->LocalGenerator->GetGlobalGenerator()->GetName() == "Ninja";
+  bool is_ninja = this->LocalGenerator->GetGlobalGenerator()->IsNinja();
 
   if (have_rpath && is_ninja) {
     std::ostringstream w;
     /* clang-format off */
     w <<
-      "The install of the " << this->GetName() << " target requires "
-      "changing an RPATH from the build tree, but this is not supported "
-      "with the Ninja generator unless on an ELF-based platform.  The "
-      "CMAKE_BUILD_WITH_INSTALL_RPATH variable may be set to avoid this "
+      "The install of the " << this->GetName() << " target requires changing "
+      "an RPATH from the build tree, but this is not supported with the Ninja "
+      "generator unless on an ELF-based or XCOFF-based platform.  "
+      "The CMAKE_BUILD_WITH_INSTALL_RPATH variable may be set to avoid this "
       "relinking step."
       ;
     /* clang-format on */
@@ -2059,20 +2058,29 @@ bool cmGeneratorTarget::IsChrpathUsed(const std::string& config) const
     return true;
   }
 
-#if defined(CMAKE_USE_ELF_PARSER)
-  // Enable if the rpath flag uses a separator and the target uses ELF
-  // binaries.
+#if defined(CMake_USE_ELF_PARSER) || defined(CMake_USE_XCOFF_PARSER)
+  // Enable if the rpath flag uses a separator and the target uses
+  // binaries we know how to edit.
   std::string ll = this->GetLinkerLanguage(config);
   if (!ll.empty()) {
     std::string sepVar =
       cmStrCat("CMAKE_SHARED_LIBRARY_RUNTIME_", ll, "_FLAG_SEP");
     cmProp sep = this->Makefile->GetDefinition(sepVar);
     if (cmNonempty(sep)) {
-      // TODO: Add ELF check to ABI detection and get rid of
+      // TODO: Add binary format check to ABI detection and get rid of
       // CMAKE_EXECUTABLE_FORMAT.
       if (cmProp fmt =
             this->Makefile->GetDefinition("CMAKE_EXECUTABLE_FORMAT")) {
-        return (*fmt == "ELF");
+#  if defined(CMake_USE_ELF_PARSER)
+        if (*fmt == "ELF") {
+          return true;
+        }
+#  endif
+#  if defined(CMake_USE_XCOFF_PARSER)
+        if (*fmt == "XCOFF") {
+          return true;
+        }
+#  endif
       }
     }
   }
diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index 86fb228..590de26 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -438,6 +438,8 @@ public:
 
   virtual bool IsVisualStudio() const { return false; }
 
+  virtual bool IsNinja() const { return false; }
+
   /** Return true if we know the exact location of object files.
       If false, store the reason in the given string.
       This is meaningful only after EnableLanguage has been called.  */
diff --git a/Source/cmGlobalNinjaGenerator.h b/Source/cmGlobalNinjaGenerator.h
index 78fcb49..0c919ef 100644
--- a/Source/cmGlobalNinjaGenerator.h
+++ b/Source/cmGlobalNinjaGenerator.h
@@ -170,6 +170,8 @@ public:
 
   static std::string GetActualName() { return "Ninja"; }
 
+  bool IsNinja() const override { return true; }
+
   /** Get encoding used by generator for ninja files */
   codecvt::Encoding GetMakefileEncoding() const override;
 
diff --git a/Source/cmMachO.h b/Source/cmMachO.h
index be92c95..faa024b 100644
--- a/Source/cmMachO.h
+++ b/Source/cmMachO.h
@@ -7,8 +7,8 @@
 #include <iosfwd>
 #include <string>
 
-#if !defined(CMAKE_USE_MACH_PARSER)
-#  error "This file may be included only if CMAKE_USE_MACH_PARSER is enabled."
+#if !defined(CMake_USE_MACH_PARSER)
+#  error "This file may be included only if CMake_USE_MACH_PARSER is enabled."
 #endif
 
 class cmMachOInternal;
diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx
index 18c266f..0807590 100644
--- a/Source/cmSystemTools.cxx
+++ b/Source/cmSystemTools.cxx
@@ -45,14 +45,18 @@
 #  include "cmCryptoHash.h"
 #endif
 
-#if defined(CMAKE_USE_ELF_PARSER)
+#if defined(CMake_USE_ELF_PARSER)
 #  include "cmELF.h"
 #endif
 
-#if defined(CMAKE_USE_MACH_PARSER)
+#if defined(CMake_USE_MACH_PARSER)
 #  include "cmMachO.h"
 #endif
 
+#if defined(CMake_USE_XCOFF_PARSER)
+#  include "cmXCOFF.h"
+#endif
+
 #include <algorithm>
 #include <cassert>
 #include <cctype>
@@ -2317,7 +2321,7 @@ bool cmSystemTools::GuessLibrarySOName(std::string const& fullPath,
 {
 // For ELF shared libraries use a real parser to get the correct
 // soname.
-#if defined(CMAKE_USE_ELF_PARSER)
+#if defined(CMake_USE_ELF_PARSER)
   cmELF elf(fullPath.c_str());
   if (elf) {
     return elf.GetSOName(soname);
@@ -2347,7 +2351,7 @@ bool cmSystemTools::GuessLibrarySOName(std::string const& fullPath,
 bool cmSystemTools::GuessLibraryInstallName(std::string const& fullPath,
                                             std::string& soname)
 {
-#if defined(CMAKE_USE_MACH_PARSER)
+#if defined(CMake_USE_MACH_PARSER)
   cmMachO macho(fullPath.c_str());
   if (macho) {
     return macho.GetInstallName(soname);
@@ -2360,9 +2364,9 @@ bool cmSystemTools::GuessLibraryInstallName(std::string const& fullPath,
   return false;
 }
 
-#if defined(CMAKE_USE_ELF_PARSER)
-std::string::size_type cmSystemToolsFindRPath(std::string const& have,
-                                              std::string const& want)
+#if defined(CMake_USE_ELF_PARSER) || defined(CMake_USE_XCOFF_PARSER)
+std::string::size_type cmSystemToolsFindRPath(cm::string_view const& have,
+                                              cm::string_view const& want)
 {
   std::string::size_type pos = 0;
   while (pos < have.size()) {
@@ -2394,7 +2398,7 @@ std::string::size_type cmSystemToolsFindRPath(std::string const& have,
 }
 #endif
 
-#if defined(CMAKE_USE_ELF_PARSER)
+#if defined(CMake_USE_ELF_PARSER)
 struct cmSystemToolsRPathInfo
 {
   unsigned long Position;
@@ -2404,7 +2408,8 @@ struct cmSystemToolsRPathInfo
 };
 #endif
 
-#if defined(CMAKE_USE_ELF_PARSER)
+// FIXME: Dispatch if multiple formats are supported.
+#if defined(CMake_USE_ELF_PARSER)
 bool cmSystemTools::ChangeRPath(std::string const& file,
                                 std::string const& oldRPath,
                                 std::string const& newRPath,
@@ -2576,6 +2581,75 @@ bool cmSystemTools::ChangeRPath(std::string const& file,
   }
   return true;
 }
+#elif defined(CMake_USE_XCOFF_PARSER)
+bool cmSystemTools::ChangeRPath(std::string const& file,
+                                std::string const& oldRPath,
+                                std::string const& newRPath,
+                                bool removeEnvironmentRPath, std::string* emsg,
+                                bool* changed)
+{
+  if (changed) {
+    *changed = false;
+  }
+
+  bool chg = false;
+  cmXCOFF xcoff(file.c_str(), cmXCOFF::Mode::ReadWrite);
+  if (cm::optional<cm::string_view> maybeLibPath = xcoff.GetLibPath()) {
+    cm::string_view libPath = *maybeLibPath;
+    // Make sure the current rpath contains the old rpath.
+    std::string::size_type pos = cmSystemToolsFindRPath(libPath, oldRPath);
+    if (pos == std::string::npos) {
+      // If it contains the new rpath instead then it is okay.
+      if (cmSystemToolsFindRPath(libPath, newRPath) != std::string::npos) {
+        return true;
+      }
+      if (emsg) {
+        std::ostringstream e;
+        /* clang-format off */
+        e << "The current RPATH is:\n"
+          << "  " << libPath << "\n"
+          << "which does not contain:\n"
+          << "  " << oldRPath << "\n"
+          << "as was expected.";
+        /* clang-format on */
+        *emsg = e.str();
+      }
+      return false;
+    }
+
+    // The prefix is either empty or ends in a ':'.
+    cm::string_view prefix = libPath.substr(0, pos);
+    if (newRPath.empty() && !prefix.empty()) {
+      prefix.remove_suffix(1);
+    }
+
+    // The suffix is either empty or starts in a ':'.
+    cm::string_view suffix = libPath.substr(pos + oldRPath.length());
+
+    // Construct the new value which preserves the part of the path
+    // not being changed.
+    std::string newLibPath;
+    if (!removeEnvironmentRPath) {
+      newLibPath = std::string(prefix);
+    }
+    newLibPath += newRPath;
+    newLibPath += suffix;
+
+    chg = xcoff.SetLibPath(newLibPath);
+  }
+  if (!xcoff) {
+    if (emsg) {
+      *emsg = xcoff.GetErrorMessage();
+    }
+    return false;
+  }
+
+  // Everything was updated successfully.
+  if (changed) {
+    *changed = chg;
+  }
+  return true;
+}
 #else
 bool cmSystemTools::ChangeRPath(std::string const& /*file*/,
                                 std::string const& /*oldRPath*/,
@@ -2720,7 +2794,8 @@ int cmSystemTools::strverscmp(std::string const& lhs, std::string const& rhs)
   return cm_strverscmp(lhs.c_str(), rhs.c_str());
 }
 
-#if defined(CMAKE_USE_ELF_PARSER)
+// FIXME: Dispatch if multiple formats are supported.
+#if defined(CMake_USE_ELF_PARSER)
 bool cmSystemTools::RemoveRPath(std::string const& file, std::string* emsg,
                                 bool* removed)
 {
@@ -2861,6 +2936,28 @@ bool cmSystemTools::RemoveRPath(std::string const& file, std::string* emsg,
   }
   return true;
 }
+#elif defined(CMake_USE_XCOFF_PARSER)
+bool cmSystemTools::RemoveRPath(std::string const& file, std::string* emsg,
+                                bool* removed)
+{
+  if (removed) {
+    *removed = false;
+  }
+
+  cmXCOFF xcoff(file.c_str(), cmXCOFF::Mode::ReadWrite);
+  bool rm = xcoff.RemoveLibPath();
+  if (!xcoff) {
+    if (emsg) {
+      *emsg = xcoff.GetErrorMessage();
+    }
+    return false;
+  }
+
+  if (removed) {
+    *removed = rm;
+  }
+  return true;
+}
 #else
 bool cmSystemTools::RemoveRPath(std::string const& /*file*/,
                                 std::string* /*emsg*/, bool* /*removed*/)
@@ -2869,10 +2966,11 @@ bool cmSystemTools::RemoveRPath(std::string const& /*file*/,
 }
 #endif
 
+// FIXME: Dispatch if multiple formats are supported.
 bool cmSystemTools::CheckRPath(std::string const& file,
                                std::string const& newRPath)
 {
-#if defined(CMAKE_USE_ELF_PARSER)
+#if defined(CMake_USE_ELF_PARSER)
   // Parse the ELF binary.
   cmELF elf(file.c_str());
 
@@ -2894,6 +2992,15 @@ bool cmSystemTools::CheckRPath(std::string const& file,
     }
   }
   return false;
+#elif defined(CMake_USE_XCOFF_PARSER)
+  // Parse the XCOFF binary.
+  cmXCOFF xcoff(file.c_str());
+  if (cm::optional<cm::string_view> libPath = xcoff.GetLibPath()) {
+    if (cmSystemToolsFindRPath(*libPath, newRPath) != std::string::npos) {
+      return true;
+    }
+  }
+  return false;
 #else
   (void)file;
   (void)newRPath;
diff --git a/Source/cmXCOFF.cxx b/Source/cmXCOFF.cxx
new file mode 100644
index 0000000..890636e
--- /dev/null
+++ b/Source/cmXCOFF.cxx
@@ -0,0 +1,356 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmXCOFF.h"
+
+#include <algorithm>
+#include <cstddef>
+
+#include <cm/memory>
+
+#include "cmsys/FStream.hxx"
+
+#include "cmStringAlgorithms.h"
+
+// Include the XCOFF format information system header.
+#ifdef _AIX
+#  define __XCOFF32__
+#  define __XCOFF64__
+#  include <xcoff.h>
+#else
+#  error "This source may be compiled only on AIX."
+#endif
+
+class cmXCOFFInternal
+{
+public:
+  // Construct and take ownership of the file stream object.
+  cmXCOFFInternal(cmXCOFF* external, std::unique_ptr<std::iostream> fin,
+                  cmXCOFF::Mode mode)
+    : External(external)
+    , Stream(std::move(fin))
+    , Mode(mode)
+  {
+  }
+
+  // Destruct and delete the file stream object.
+  virtual ~cmXCOFFInternal() = default;
+
+  cmXCOFF::Mode GetMode() const { return this->Mode; }
+
+  virtual cm::optional<cm::string_view> GetLibPath() = 0;
+
+  virtual bool SetLibPath(cm::string_view libPath) = 0;
+  virtual bool RemoveLibPath() = 0;
+
+protected:
+  // Data common to all ELF class implementations.
+
+  // The external cmXCOFF object.
+  cmXCOFF* External;
+
+  // The stream from which to read.
+  std::unique_ptr<std::iostream> Stream;
+
+  cmXCOFF::Mode Mode;
+
+  // Helper methods for subclasses.
+  void SetErrorMessage(const char* msg) { this->External->ErrorMessage = msg; }
+};
+
+namespace {
+
+struct XCOFF32
+{
+  typedef struct filehdr filehdr;
+  typedef struct aouthdr aouthdr;
+  typedef struct scnhdr scnhdr;
+  typedef struct ldhdr ldhdr;
+  static const std::size_t aouthdr_size = _AOUTHSZ_EXEC;
+};
+const unsigned char xcoff32_magic[] = { 0x01, 0xDF };
+
+struct XCOFF64
+{
+  typedef struct filehdr_64 filehdr;
+  typedef struct aouthdr_64 aouthdr;
+  typedef struct scnhdr_64 scnhdr;
+  typedef struct ldhdr_64 ldhdr;
+  static const std::size_t aouthdr_size = _AOUTHSZ_EXEC_64;
+};
+const unsigned char xcoff64_magic[] = { 0x01, 0xF7 };
+
+template <typename XCOFF>
+class Impl : public cmXCOFFInternal
+{
+  static_assert(sizeof(typename XCOFF::aouthdr) == XCOFF::aouthdr_size,
+                "aouthdr structure size matches _AOUTHSZ_EXEC macro");
+
+  typename XCOFF::filehdr FileHeader;
+  typename XCOFF::aouthdr AuxHeader;
+  typename XCOFF::scnhdr LoaderSectionHeader;
+  typename XCOFF::ldhdr LoaderHeader;
+
+  std::streamoff LoaderImportFileTablePos = 0;
+  std::vector<char> LoaderImportFileTable;
+
+  bool Read(typename XCOFF::filehdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool Read(typename XCOFF::aouthdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool Read(typename XCOFF::scnhdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool Read(typename XCOFF::ldhdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool WriteLoaderImportFileTableLength(decltype(XCOFF::ldhdr::l_istlen) x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->write(reinterpret_cast<char const*>(&x), sizeof(x)));
+  }
+
+public:
+  Impl(cmXCOFF* external, std::unique_ptr<std::iostream> fin,
+       cmXCOFF::Mode mode);
+
+  cm::optional<cm::string_view> GetLibPath() override;
+  bool SetLibPath(cm::string_view libPath) override;
+  bool RemoveLibPath() override;
+};
+
+template <typename XCOFF>
+Impl<XCOFF>::Impl(cmXCOFF* external, std::unique_ptr<std::iostream> fin,
+                  cmXCOFF::Mode mode)
+  : cmXCOFFInternal(external, std::move(fin), mode)
+{
+  if (!this->Read(this->FileHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF file header.");
+    return;
+  }
+  if (this->FileHeader.f_opthdr != XCOFF::aouthdr_size) {
+    this->SetErrorMessage("XCOFF auxiliary header missing.");
+    return;
+  }
+  if (!this->Read(this->AuxHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF auxiliary header.");
+    return;
+  }
+  if (this->AuxHeader.o_snloader == 0) {
+    this->SetErrorMessage("XCOFF loader section missing.");
+    return;
+  }
+  if (!this->Stream->seekg((this->AuxHeader.o_snloader - 1) *
+                             sizeof(typename XCOFF::scnhdr),
+                           std::ios::cur)) {
+    this->SetErrorMessage("Failed to seek to XCOFF loader section header.");
+    return;
+  }
+  if (!this->Read(this->LoaderSectionHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF loader section header.");
+    return;
+  }
+  if ((this->LoaderSectionHeader.s_flags & STYP_LOADER) == 0) {
+    this->SetErrorMessage("XCOFF loader section header missing STYP_LOADER.");
+    return;
+  }
+  if (!this->Stream->seekg(this->LoaderSectionHeader.s_scnptr,
+                           std::ios::beg)) {
+    this->SetErrorMessage("Failed to seek to XCOFF loader header.");
+    return;
+  }
+  if (!this->Read(this->LoaderHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF loader header.");
+    return;
+  }
+  this->LoaderImportFileTablePos =
+    this->LoaderSectionHeader.s_scnptr + this->LoaderHeader.l_impoff;
+  if (!this->Stream->seekg(this->LoaderImportFileTablePos)) {
+    this->SetErrorMessage(
+      "Failed to seek to XCOFF loader import file id table.");
+    return;
+  }
+  this->LoaderImportFileTable.resize(this->LoaderHeader.l_istlen);
+  if (!this->Stream->read(this->LoaderImportFileTable.data(),
+                          this->LoaderImportFileTable.size())) {
+    this->SetErrorMessage("Failed to read XCOFF loader import file id table.");
+    return;
+  }
+}
+
+template <typename XCOFF>
+cm::optional<cm::string_view> Impl<XCOFF>::GetLibPath()
+{
+  cm::optional<cm::string_view> result;
+  auto end = std::find(this->LoaderImportFileTable.begin(),
+                       this->LoaderImportFileTable.end(), '\0');
+  if (end != this->LoaderImportFileTable.end()) {
+    result = cm::string_view(this->LoaderImportFileTable.data(),
+                             end - this->LoaderImportFileTable.begin());
+  }
+  return result;
+}
+
+template <typename XCOFF>
+bool Impl<XCOFF>::SetLibPath(cm::string_view libPath)
+{
+  // The new LIBPATH must end in the standard AIX LIBPATH.
+#define CM_AIX_LIBPATH "/usr/lib:/lib"
+  std::string libPathBuf;
+  if (libPath != CM_AIX_LIBPATH &&
+      !cmHasLiteralSuffix(libPath, ":" CM_AIX_LIBPATH)) {
+    libPathBuf = std::string(libPath);
+    if (!libPathBuf.empty() && libPathBuf.back() != ':') {
+      libPathBuf.push_back(':');
+    }
+    libPathBuf += CM_AIX_LIBPATH;
+    libPath = libPathBuf;
+  }
+#undef CM_AIX_LIBPATH
+
+  auto oldEnd = std::find(this->LoaderImportFileTable.begin(),
+                          this->LoaderImportFileTable.end(), '\0');
+  if (oldEnd == this->LoaderImportFileTable.end()) {
+    this->SetErrorMessage("XCOFF loader import file id table is invalid.");
+    return false;
+  }
+  if ((this->LoaderImportFileTable.begin() + libPath.size()) > oldEnd) {
+    this->SetErrorMessage("XCOFF loader import file id table is too small.");
+    return false;
+  }
+
+  {
+    std::vector<char> ift;
+    ift.reserve(this->LoaderImportFileTable.size());
+    // Start with the new LIBPATH.
+    ift.insert(ift.end(), libPath.begin(), libPath.end());
+    // Add the rest of the original table.
+    ift.insert(ift.end(), oldEnd, this->LoaderImportFileTable.end());
+    // If the new table is shorter, zero out the leftover space.
+    ift.resize(this->LoaderImportFileTable.size(), 0);
+    this->LoaderHeader.l_istlen =
+      static_cast<decltype(XCOFF::ldhdr::l_istlen)>(ift.size());
+    this->LoaderImportFileTable = std::move(ift);
+  }
+
+  if (!this->Stream->seekp(this->LoaderSectionHeader.s_scnptr +
+                             offsetof(typename XCOFF::ldhdr, l_istlen),
+                           std::ios::beg)) {
+    this->SetErrorMessage(
+      "Failed to seek to XCOFF loader header import file id table length.");
+    return false;
+  }
+  if (!this->WriteLoaderImportFileTableLength(this->LoaderHeader.l_istlen)) {
+    this->SetErrorMessage(
+      "Failed to write XCOFF loader header import file id table length.");
+    return false;
+  }
+  if (!this->Stream->seekp(this->LoaderImportFileTablePos, std::ios::beg)) {
+    this->SetErrorMessage(
+      "Failed to seek to XCOFF loader import file id table.");
+    return false;
+  }
+  if (!this->Stream->write(this->LoaderImportFileTable.data(),
+                           this->LoaderImportFileTable.size())) {
+    this->SetErrorMessage(
+      "Failed to write XCOFF loader import file id table.");
+    return false;
+  }
+
+  return true;
+}
+
+template <typename XCOFF>
+bool Impl<XCOFF>::RemoveLibPath()
+{
+  return this->SetLibPath({});
+}
+}
+
+//============================================================================
+// External class implementation.
+
+cmXCOFF::cmXCOFF(const char* fname, Mode mode)
+{
+  // Try to open the file.
+  std::ios::openmode fmode = std::ios::in | std::ios::binary;
+  if (mode == Mode::ReadWrite) {
+    fmode |= std::ios::out;
+  }
+  auto f = cm::make_unique<cmsys::fstream>(fname, fmode);
+
+  // Quit now if the file could not be opened.
+  if (!f || !*f) {
+    this->ErrorMessage = "Error opening input file.";
+    return;
+  }
+
+  // Read the XCOFF magic number.
+  unsigned char magic[2];
+  if (!f->read(reinterpret_cast<char*>(magic), sizeof(magic))) {
+    this->ErrorMessage = "Error reading XCOFF magic number.";
+    return;
+  }
+  if (!f->seekg(0)) {
+    this->ErrorMessage = "Error seeking to beginning of file.";
+    return;
+  }
+
+  // Check the XCOFF type.
+  if (magic[0] == xcoff32_magic[0] && magic[1] == xcoff32_magic[1]) {
+    this->Internal = cm::make_unique<Impl<XCOFF32>>(this, std::move(f), mode);
+  } else if (magic[0] == xcoff64_magic[0] && magic[1] == xcoff64_magic[1]) {
+    this->Internal = cm::make_unique<Impl<XCOFF64>>(this, std::move(f), mode);
+  } else {
+    this->ErrorMessage = "File is not a XCOFF32 or XCOFF64 binary.";
+  }
+}
+
+cmXCOFF::~cmXCOFF() = default;
+
+cmXCOFF::cmXCOFF(cmXCOFF&&) = default;
+cmXCOFF& cmXCOFF::operator=(cmXCOFF&&) = default;
+
+bool cmXCOFF::Valid() const
+{
+  return this->Internal && this->ErrorMessage.empty();
+}
+
+cm::optional<cm::string_view> cmXCOFF::GetLibPath() const
+{
+  cm::optional<cm::string_view> result;
+  if (this->Valid()) {
+    result = this->Internal->GetLibPath();
+  }
+  return result;
+}
+
+bool cmXCOFF::SetLibPath(cm::string_view libPath)
+{
+  return this->Valid() && this->Internal->GetMode() == Mode::ReadWrite &&
+    this->Internal->SetLibPath(libPath);
+}
+
+bool cmXCOFF::RemoveLibPath()
+{
+  return this->Valid() && this->Internal->GetMode() == Mode::ReadWrite &&
+    this->Internal->RemoveLibPath();
+}
diff --git a/Source/cmXCOFF.h b/Source/cmXCOFF.h
new file mode 100644
index 0000000..16cda9d
--- /dev/null
+++ b/Source/cmXCOFF.h
@@ -0,0 +1,65 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#pragma once
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include <iosfwd>
+#include <memory>
+#include <string>
+
+#include <cm/optional>
+#include <cm/string_view>
+
+#if !defined(CMake_USE_XCOFF_PARSER)
+#  error "This file may be included only if CMake_USE_XCOFF_PARSER is enabled."
+#endif
+
+class cmXCOFFInternal;
+
+/** \class cmXCOFF
+ * \brief XCOFF parser.
+ */
+class cmXCOFF
+{
+public:
+  enum class Mode
+  {
+    ReadOnly,
+    ReadWrite
+  };
+
+  /** Construct with the name of the XCOFF input file to parse.  */
+  cmXCOFF(const char* fname, Mode = Mode::ReadOnly);
+
+  /** Destruct.   */
+  ~cmXCOFF();
+
+  cmXCOFF(cmXCOFF&&);
+  cmXCOFF(cmXCOFF const&) = delete;
+  cmXCOFF& operator=(cmXCOFF&&);
+  cmXCOFF& operator=(cmXCOFF const&) = delete;
+
+  /** Get the error message if any.  */
+  std::string const& GetErrorMessage() const { return this->ErrorMessage; }
+
+  /** Boolean conversion.  True if the XCOFF file is valid.  */
+  explicit operator bool() const { return this->Valid(); }
+
+  /** Get the LIBPATH (RPATH) parsed from the file, if any.  */
+  cm::optional<cm::string_view> GetLibPath() const;
+
+  /** Set the LIBPATH (RPATH).
+      Works only if cmXCOFF was constructed with Mode::ReadWrite.  */
+  bool SetLibPath(cm::string_view libPath);
+
+  /** Remove the LIBPATH (RPATH).
+      Works only if cmXCOFF was constructed with Mode::ReadWrite.  */
+  bool RemoveLibPath();
+
+private:
+  friend class cmXCOFFInternal;
+  bool Valid() const;
+  std::unique_ptr<cmXCOFFInternal> Internal;
+  std::string ErrorMessage;
+};