[SystemZ][z/OS] Add missing strnlen function for z/OS to fix build failures (#75339)

This patch adds strnlen to the zOSSupport.h file to fix build failures in multiple files.

Author: abhina-sree

Diff for: clang/lib/Lex/HeaderMap.cpp

@@ -11,16 +11,17 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Lex/HeaderMap.h"
-#include "clang/Lex/HeaderMapTypes.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/FileManager.h"
+#include "clang/Lex/HeaderMapTypes.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/DataTypes.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SwapByteOrder.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include <cstring>
 #include <memory>
 #include <optional>

Diff for: llvm/include/llvm/Support/SystemZ/zOSSupport.h

@@ -35,5 +35,13 @@ inline pid_t wait4(pid_t pid, int *wstatus, int options,
   return Result;
 }
 
+// z/OS Unix System Services does not have strnlen() support, so the strnlen()
+// function is implemented here.
+inline std::size_t strnlen(const char *S, std::size_t MaxLen) {
+  const char *PtrToNullChar =
+      static_cast<const char *>(std::memchr(S, '\0', MaxLen));
+  return PtrToNullChar ? PtrToNullChar - S : MaxLen;
+}
+
 #endif
 #endif

Diff for: llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.cpp

@@ -10,6 +10,7 @@
 #include "llvm/Support/Alignment.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 
 using namespace llvm;
 using namespace llvm::objcopy::macho;

Diff for: llvm/lib/ObjCopy/MachO/MachOObject.cpp

@@ -8,6 +8,7 @@
 
 #include "MachOObject.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include <unordered_set>
 
 using namespace llvm;

Diff for: llvm/lib/ObjCopy/MachO/MachOReader.cpp

@@ -11,6 +11,7 @@
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Support/Errc.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include <memory>
 
 using namespace llvm;

Diff for: llvm/lib/ObjectYAML/MachOEmitter.cpp

@@ -19,6 +19,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include "llvm/Support/YAMLTraits.h"
 #include "llvm/Support/raw_ostream.h"
 

Diff for: llvm/lib/ObjectYAML/MachOYAML.cpp

@@ -14,6 +14,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include "llvm/Support/YAMLTraits.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/Host.h"

Diff for: llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp

@@ -25,6 +25,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/Signals.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 
 #ifdef __linux__
 #ifdef HAVE_LIBPFM

Diff for: llvm/tools/llvm-exegesis/lib/Error.cpp

@@ -9,6 +9,7 @@
 #include "Error.h"
 
 #ifdef LLVM_ON_UNIX
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include <string.h>
 #endif // LLVM_ON_UNIX
 

Diff for: llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -57,6 +57,7 @@
 #include "llvm/Support/RISCVAttributeParser.h"
 #include "llvm/Support/RISCVAttributes.h"
 #include "llvm/Support/ScopedPrinter.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cinttypes>

Diff for: llvm/tools/llvm-readobj/ObjDumper.cpp

@@ -18,6 +18,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ScopedPrinter.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 #include "llvm/Support/raw_ostream.h"
 #include <map>
 

Diff for: llvm/tools/obj2yaml/macho2yaml.cpp

@@ -15,6 +15,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/SystemZ/zOSSupport.h"
 
 #include <string.h> // for memcpy