mfbt/Types.h
author Dão Gottwald <dao@mozilla.com>
Wed, 20 Feb 2019 07:20:52 +0000
changeset 516104 b9fe883c6c1eb27d2e16aceba083b8081ec6f944
parent 514505 5f4630838d46dd81dadb13220a4af0da9e23a619
permissions -rw-r--r--
Bug 1504766 - Let explicit Dark and Light themes ignore the Windows 10 setting for accent color in title bars. r=ntim,Gijs a=lizzard Differential Revision: https://phabricator.services.mozilla.com/D19764

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* mfbt foundational types and macros. */

#ifndef mozilla_Types_h
#  define mozilla_Types_h

/*
 * This header must be valid C and C++, includable by code embedding either
 * SpiderMonkey or Gecko.
 */

/* Expose all <stdint.h> types and size_t. */
#  include <stddef.h>
#  include <stdint.h>

/* Implement compiler and linker macros needed for APIs. */

/*
 * MOZ_EXPORT is used to declare and define a symbol or type which is externally
 * visible to users of the current library.  It encapsulates various decorations
 * needed to properly export the method's symbol.
 *
 *   api.h:
 *     extern MOZ_EXPORT int MeaningOfLife(void);
 *     extern MOZ_EXPORT int LuggageCombination;
 *
 *   api.c:
 *     int MeaningOfLife(void) { return 42; }
 *     int LuggageCombination = 12345;
 *
 * If you are merely sharing a method across files, just use plain |extern|.
 * These macros are designed for use by library interfaces -- not for normal
 * methods or data used cross-file.
 */
#  if defined(WIN32)
#    define MOZ_EXPORT __declspec(dllexport)
#  else /* Unix */
#    ifdef HAVE_VISIBILITY_ATTRIBUTE
#      define MOZ_EXPORT __attribute__((visibility("default")))
#    elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
#      define MOZ_EXPORT __global
#    else
#      define MOZ_EXPORT /* nothing */
#    endif
#  endif

/*
 * Whereas implementers use MOZ_EXPORT to declare and define library symbols,
 * users use MOZ_IMPORT_API and MOZ_IMPORT_DATA to access them.  Most often the
 * implementer of the library will expose an API macro which expands to either
 * the export or import version of the macro, depending upon the compilation
 * mode.
 */
#  ifdef _WIN32
#    if defined(__MWERKS__)
#      define MOZ_IMPORT_API /* nothing */
#    else
#      define MOZ_IMPORT_API __declspec(dllimport)
#    endif
#  else
#    define MOZ_IMPORT_API MOZ_EXPORT
#  endif

#  if defined(_WIN32) && !defined(__MWERKS__)
#    define MOZ_IMPORT_DATA __declspec(dllimport)
#  else
#    define MOZ_IMPORT_DATA MOZ_EXPORT
#  endif

/*
 * Consistent with the above comment, the MFBT_API and MFBT_DATA macros expose
 * export mfbt declarations when building mfbt, and they expose import mfbt
 * declarations when using mfbt.
 */
#  if defined(IMPL_MFBT) ||                              \
      (defined(JS_STANDALONE) && !defined(MOZ_MEMORY) && \
       (defined(EXPORT_JS_API) || defined(STATIC_EXPORTABLE_JS_API)))
#    define MFBT_API MOZ_EXPORT
#    define MFBT_DATA MOZ_EXPORT
#  else
#    if defined(JS_STANDALONE) && !defined(MOZ_MEMORY) && defined(STATIC_JS_API)
#      define MFBT_API
#      define MFBT_DATA
#    else
/*
 * On linux mozglue is linked in the program and we link libxul.so with
 * -z,defs. Normally that causes the linker to reject undefined references in
 * libxul.so, but as a loophole it allows undefined references to weak
 * symbols. We add the weak attribute to the import version of the MFBT API
 * macros to exploit this.
 */
#      if defined(MOZ_GLUE_IN_PROGRAM)
#        define MFBT_API __attribute__((weak)) MOZ_IMPORT_API
#        define MFBT_DATA __attribute__((weak)) MOZ_IMPORT_DATA
#      else
#        define MFBT_API MOZ_IMPORT_API
#        define MFBT_DATA MOZ_IMPORT_DATA
#      endif
#    endif
#  endif

/*
 * C symbols in C++ code must be declared immediately within |extern "C"|
 * blocks.  However, in C code, they need not be declared specially.  This
 * difference is abstracted behind the MOZ_BEGIN_EXTERN_C and MOZ_END_EXTERN_C
 * macros, so that the user need not know whether he is being used in C or C++
 * code.
 *
 *   MOZ_BEGIN_EXTERN_C
 *
 *   extern MOZ_EXPORT int MostRandomNumber(void);
 *   ...other declarations...
 *
 *   MOZ_END_EXTERN_C
 *
 * This said, it is preferable to just use |extern "C"| in C++ header files for
 * its greater clarity.
 */
#  ifdef __cplusplus
#    define MOZ_BEGIN_EXTERN_C extern "C" {
#    define MOZ_END_EXTERN_C }
#  else
#    define MOZ_BEGIN_EXTERN_C
#    define MOZ_END_EXTERN_C
#  endif

/*
 * GCC's typeof is available when decltype is not.
 */
#  if defined(__GNUC__) && defined(__cplusplus) && \
      !defined(__GXX_EXPERIMENTAL_CXX0X__) && __cplusplus < 201103L
#    define decltype __typeof__
#  endif

#endif /* mozilla_Types_h */