如何在 GCC 中编译 Objective C++？

Question

我在 Ubuntu 16.04 中安装了 GNUStep 和 gobjc。我可以像这样编译 Objective-C 代码：

gcc codefile.m `gnustep-config --objc-flags` -lobjc -lgnustep-base -o codefile

但我想在 GCC 中编译 Objective-C++ 代码。我该怎么做？

Answer 1

Documentation of objc/objc++ dialects in GCC of your version of gcc / gobjc 不列出 select 方言变体的特定选项。

只需使用标准文件扩展名“.mm”或“.M”（此外，您可以将 gcc 替换为 g++ 以自动将 C++ 库添加到链接阶段；两种变体都未经测试）：

gcc codefile.mm `gnustep-config --objc-flags` -lobjc -lgnustep-base -o codefile
g++ codefile.mm `gnustep-config --objc-flags` -lobjc -lgnustep-base -o codefile

而 ObjC++ 是 "simply source code that mixes Objective-C classes and C++ classes"

Gcc 会根据文件扩展名 select 模式，有大量 table 的文件扩展名和相应的语言模式 Objective-C for .m and Objective-C++ .mm/.M: https://github.com/gcc-mirror/gcc/blob/gcc-4_7_4-release/gcc/gcc.c#L913

static const struct compiler default_compilers[] =
{
  /* Add lists of suffixes of known languages here.  If those languages
     were not present when we built the driver, we will hit these copies
     and be given a more meaningful error than "file not used since
     linking is not done".  */
  {".m",  "#Objective-C", 0, 0, 0}, {".mi",  "#Objective-C", 0, 0, 0},
  {".mm", "#Objective-C++", 0, 0, 0}, {".M", "#Objective-C++", 0, 0, 0},
  {".mii", "#Objective-C++", 0, 0, 0},
 . . .
  /* Next come the entries for C.  */
  {".c", "@c", 0, 0, 1},

还有 g++ 的 -x 选项，允许参数 "objective-c++" 手动 select 语言方言（gcc -x objective-c++ ... 或 g++ -x objective-c++ ): https://github.com/gcc-mirror/gcc/blob/1cb6c2eb3b8361d850be8e8270c597270a1a7967/gcc/cp/g%2B%2Bspec.c#L167

case OPT_x:
 . . . 
      && (strcmp (arg, "c++") == 0
      || strcmp (arg, "c++-cpp-output") == 0
      || strcmp (arg, "objective-c++") == 0

记录在 https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html

 -x language
Specify explicitly the language for the following input files (rather than letting the compiler choose a default based on the file name suffix). This option applies to all following input files until the next -x option. Possible values for language are:
      c  . . .  c++ . . .
      objective-c  objective-c-header  objective-c-cpp-output
      objective-c++ objective-c++-header objective-c++-cpp-output

如何在 GCC 中编译 Objective C++？

How to compile Objective C++ in GCC?

linux

gcc

g++

objective-c++