Fixes issue #21 "to create an automatic symbolic map for enum values."

[Clang] Add support for -symbolic-map to automatically generate symbolic name tables for enumerators

Summary

This patch introduces a new Clang option -symbolic-map that enables automatic generation of global string name tables for C/C++ enumerators. When this flag is enabled, Clang emits a global variable for each named, defined enum (including enum class and enum struct), mapping enumerator values to their symbolic string names.

Example

Given the enum:

enum Day {
    Monday,
    Tuesday,
    Wednesday
};

Clang will emit the following global variable into the object file:

const char *__nameof_Day[] = {
    "Monday",
    "Tuesday",
    "Wednesday"
};

The symbol __nameof_Day will be available in the object file and can be inspected via nm or objdump.

Implementation

CodeGenModule.cpp

• Added a new method EmitEnumSymbolicMap(const EnumDecl *ED) to emit a global constant array of string literals for the enumerator names.
• Skips unnamed, empty, or forward-declared enums.
• Uses GetAddrOfConstantCString to obtain LLVM constant string pointers.
• The array is emitted with WeakODR linkage and pointer-aligned.

CodeGenModule.h

• Declared the new function:

  void EmitEnumSymbolicMap(const EnumDecl *ED);

Options.td

• Introduced a new frontend flag:

  def symbolic_map : Flag<["-"], "symbolic-map">,
    Group<f_Group>,
    Visibility<[ClangOption, CC1Option]>,
    HelpText<"Automatically generate a map of symbolic names for enumerators">,
    MarshallingInfoFlag<LangOpts<"SymbolicMap">>;
  

LangOptions.def

• Added a new language option:

  LANGOPT(SymbolicMap, 1, 0, "Automatically generate a map of symbolic names for enumerators")

Logic Summary

The symbolic map is generated only if:

• The enum is named and not anonymous.
• It is a definition (not a forward declaration).
• It contains at least one enumerator.

Scoped and unscoped enums are both supported.

Symbol Emission

For the following enum:

enum class Color { Red, Green, Blue };

The object file will contain a global variable named:

__nameof_Color

Output: