symbol_exports.hpp

// Copyright (c) TrajoptLib contributors
 
#pragma once
 
#ifdef _WIN32
#ifdef _MSC_VER
#pragma warning(disable : 4251)
#endif
 
#ifdef TRAJOPT_EXPORTS
#ifdef __GNUC__
#define TRAJOPT_DLLEXPORT __attribute__((dllexport))
#else
#define TRAJOPT_DLLEXPORT __declspec(dllexport)
#endif
 
#elif defined(TRAJOPT_IMPORTS)
 
#ifdef __GNUC__
#define TRAJOPT_DLLEXPORT __attribute__((dllimport))
#else
#define TRAJOPT_DLLEXPORT __declspec(dllimport)
#endif
 
#else
#define TRAJOPT_DLLEXPORT
#endif
 
#else  // _WIN32
 
#ifdef TRAJOPT_EXPORTS
#define TRAJOPT_DLLEXPORT __attribute__((visibility("default")))
#else
#define TRAJOPT_DLLEXPORT
#endif
 
#endif  // _WIN32
 
// Synopsis
//
// This header provides macros for using FOO_EXPORT macros with explicit
// template instantiation declarations and definitions.
// Generally, the FOO_EXPORT macros are used at declarations,
// and GCC requires them to be used at explicit instantiation declarations,
// but MSVC requires __declspec(dllexport) to be used at the explicit
// instantiation definitions instead.
 
// Usage
//
// In a header file, write:
//
//   extern template class EXPORT_TEMPLATE_DECLARE(FOO_EXPORT) foo<bar>;
//
// In a source file, write:
//
//   template class EXPORT_TEMPLATE_DEFINE(FOO_EXPORT) foo<bar>;
 
// Implementation notes
//
// The implementation of this header uses some subtle macro semantics to
// detect what the provided FOO_EXPORT value was defined as and then
// to dispatch to appropriate macro definitions.  Unfortunately,
// MSVC's C preprocessor is rather non-compliant and requires special
// care to make it work.
//
// Issue 1.
//
//   #define F(x)
//   F()
//
// MSVC emits warning C4003 ("not enough actual parameters for macro
// 'F'), even though it's a valid macro invocation.  This affects the
// macros below that take just an "export" parameter, because export
// may be empty.
//
// As a workaround, we can add a dummy parameter and arguments:
//
//   #define F(x,_)
//   F(,)
//
// Issue 2.
//
//   #define F(x) G##x
//   #define Gj() ok
//   F(j())
//
// The correct replacement for "F(j())" is "ok", but MSVC replaces it
// with "Gj()".  As a workaround, we can pass the result to an
// identity macro to force MSVC to look for replacements again.  (This
// is why EXPORT_TEMPLATE_STYLE_3 exists.)
 
#define EXPORT_TEMPLATE_DECLARE(export) \
  EXPORT_TEMPLATE_INVOKE(DECLARE, EXPORT_TEMPLATE_STYLE(export, ), export)
#define EXPORT_TEMPLATE_DEFINE(export) \
  EXPORT_TEMPLATE_INVOKE(DEFINE, EXPORT_TEMPLATE_STYLE(export, ), export)
 
// INVOKE is an internal helper macro to perform parameter replacements
// and token pasting to chain invoke another macro.  E.g.,
//     EXPORT_TEMPLATE_INVOKE(DECLARE, DEFAULT, FOO_EXPORT)
// will export to call
//     EXPORT_TEMPLATE_DECLARE_DEFAULT(FOO_EXPORT, )
// (but with FOO_EXPORT expanded too).
#define EXPORT_TEMPLATE_INVOKE(which, style, export) \
  EXPORT_TEMPLATE_INVOKE_2(which, style, export)
#define EXPORT_TEMPLATE_INVOKE_2(which, style, export) \
  EXPORT_TEMPLATE_##which##_##style(export, )
 
// Default style is to apply the FOO_EXPORT macro at declaration sites.
#define EXPORT_TEMPLATE_DECLARE_DEFAULT(export, _) export
#define EXPORT_TEMPLATE_DEFINE_DEFAULT(export, _)
 
// The "MSVC hack" style is used when FOO_EXPORT is defined
// as __declspec(dllexport), which MSVC requires to be used at
// definition sites instead.
#define EXPORT_TEMPLATE_DECLARE_MSVC_HACK(export, _)
#define EXPORT_TEMPLATE_DEFINE_MSVC_HACK(export, _) export
 
// EXPORT_TEMPLATE_STYLE is an internal helper macro that identifies which
// export style needs to be used for the provided FOO_EXPORT macro definition.
// "", "__attribute__(...)", and "__declspec(dllimport)" are mapped
// to "DEFAULT"; while "__declspec(dllexport)" is mapped to "MSVC_HACK".
//
// It's implemented with token pasting to transform the __attribute__ and
// __declspec annotations into macro invocations.  E.g., if FOO_EXPORT is
// defined as "__declspec(dllimport)", it undergoes the following sequence of
// macro substitutions:
//     EXPORT_TEMPLATE_STYLE(FOO_EXPORT, )
//     EXPORT_TEMPLATE_STYLE_2(__declspec(dllimport), )
//     EXPORT_TEMPLATE_STYLE_3(EXPORT_TEMPLATE_STYLE_MATCH__declspec(dllimport))
//     EXPORT_TEMPLATE_STYLE_MATCH__declspec(dllimport)
//     EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport
//     DEFAULT
#define EXPORT_TEMPLATE_STYLE(export, _) EXPORT_TEMPLATE_STYLE_2(export, )
#define EXPORT_TEMPLATE_STYLE_2(export, _) \
  EXPORT_TEMPLATE_STYLE_3(                 \
      EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA##export)
#define EXPORT_TEMPLATE_STYLE_3(style) style
 
// Internal helper macros for EXPORT_TEMPLATE_STYLE.
//
// XXX: C++ reserves all identifiers containing "__" for the implementation,
// but "__attribute__" and "__declspec" already contain "__" and the token-paste
// operator can only add characters; not remove them.  To minimize the risk of
// conflict with implementations, we include "foj3FJo5StF0OvIzl7oMxA" (a random
// 128-bit string, encoded in Base64) in the macro name.
#define EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA DEFAULT
#define EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__attribute__(...) \
  DEFAULT
#define EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__declspec(arg) \
  EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_##arg
 
// Internal helper macros for EXPORT_TEMPLATE_STYLE.
#define EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllexport MSVC_HACK
#define EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport DEFAULT