[XCOFF] Clean-up enum use in BinaryFormat/XCOFF.h; NFC

[hubert.reinterpretcast]

Summary

This patch splits mostly unrelated size constants into separate constexpr variables, sets explicit underlying types for the enumerations to match the fields they are used for, and improves various comments.

This patch also replaces <cname> headers with <name.h> headers to match the usage of the declared names as global namespace members in the file.

[jasonliu]

LGTM.

[sfertile]

LGTM.

[jasonliu]

llvm/include/llvm/BinaryFormat/XCOFF.h

25

nit: remove blank line?

[hubert.reinterpretcast]

llvm/include/llvm/BinaryFormat/XCOFF.h

25

The blank line is intentional on my part. This comment describes more than just the immediate block of declarations.

[jasonliu]

llvm/include/llvm/BinaryFormat/XCOFF.h

25

Okay.

llvm/include/llvm/BinaryFormat/XCOFF.h

 //===-- llvm/BinaryFormat/XCOFF.h - The XCOFF file format -------*- C++/-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines manifest constants for the XCOFF object file format.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_BINARYFORMAT_XCOFF_H
 #define LLVM_BINARYFORMAT_XCOFF_H
 
-#include <cstdint>
+#include <stddef.h>
+#include <stdint.h>
 
 namespace llvm {
 class StringRef;
 
 namespace XCOFF {
 
 // Constants used in the XCOFF definition.
-enum {
-  FileNamePadSize = 6,
-  NameSize = 8,
-  SymbolTableEntrySize = 18,
-  RelocationSerializationSize32 = 10
-};
 
-enum ReservedSectionNum { N_DEBUG = -2, N_ABS = -1, N_UNDEF = 0 };
+constexpr size_t FileNamePadSize = 6;
+constexpr size_t NameSize = 8;
+constexpr size_t SymbolTableEntrySize = 18;
+constexpr size_t RelocationSerializationSize32 = 10;
+
+enum ReservedSectionNum : int16_t { N_DEBUG = -2, N_ABS = -1, N_UNDEF = 0 };
 
 // x_smclas field of x_csect from system header: /usr/include/syms.h
 /// Storage Mapping Class definitions.
 enum StorageMappingClass : uint8_t {
   //     READ ONLY CLASSES
   XMC_PR = 0,      ///< Program Code
   XMC_RO = 1,      ///< Read Only Constant
   XMC_DB = 2,      ///< Debug Dictionary Table
enum StorageMappingClass : uint8_t {
   XMC_BS = 9,   ///< BSS class (uninitialized static internal)
   XMC_UC = 11,  ///< Un-named Fortran Common
 
   XMC_TL = 20, ///< Initialized thread-local variable
   XMC_UL = 21, ///< Uninitialized thread-local variable
   XMC_TE = 22  ///< Symbol mapped at the end of TOC
 };
 
-// Flags for defining the section type. Used for the s_flags field of
-// the section header structure. Defined in the system header `scnhdr.h`.
-enum SectionTypeFlags {
+// Flags for defining the section type. Masks for use with the (signed, 32-bit)
+// s_flags field of the section header structure, selecting for values in the
+// lower 16 bits. Defined in the system header `scnhdr.h`.
+enum SectionTypeFlags : int32_t {
   STYP_PAD = 0x0008,
   STYP_DWARF = 0x0010,
   STYP_TEXT = 0x0020,
   STYP_DATA = 0x0040,
   STYP_BSS = 0x0080,
   STYP_EXCEPT = 0x0100,
   STYP_INFO = 0x0200,
   STYP_TDATA = 0x0400,
enum StorageClass : uint8_t {
   C_ALIAS = 105,  // Duplicate tag
   C_HIDDEN = 106, // Special storage class for external
   C_EFCN = 255,   // Physical end of function
 
   // Storage classes - reserved
   C_TCSYM = 134 // Reserved
 };
 
-enum SymbolType {
+// Flags for defining the symbol type. Values to be encoded into the lower 3
+// bits of the (unsigned, 8-bit) x_smtyp field of csect auxiliary symbol table
+// entries. Defined in the system header `syms.h`.
+enum SymbolType : uint8_t {
   XTY_ER = 0, ///< External reference.
   XTY_SD = 1, ///< Csect definition for initialized storage.
   XTY_LD = 2, ///< Label definition.
               ///< Defines an entry point to an initialized csect.
   XTY_CM = 3  ///< Common csect definition. For uninitialized storage.
 };
 
 // Relocation types, defined in `/usr/include/reloc.h`.