在OSX上预编译的头文件和编译通用对象

Question

我们在项目中使用GCC预编译头文件,并按如下方式构建它们:

gcc $(CFLAGS) precompiledcommonlib.h

现在我正在OSX 10.6上构建项目,并尝试同时使用为所有体系结构构建的漂亮功能,如下所示:

gcc $(CFLAGS) -c -arch i386 -arch x86_64 commonlib.c  

但是,似乎这对预编译的头文件不起作用:

gcc $(CFLAGS) -arch i386 -arch x86_64 precompiledcommonlib.h
Undefined symbols for architecture i386:
  "_main", referenced from:
      start in crt1.10.6.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status
Undefined symbols for architecture x86_64:
  "_main", referenced from:
      start in crt1.10.6.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
lipo: can't open input file: /var/folders/z1/z1A0sPkqGDyPrZWo9ysVK++++TI/-Tmp-//cc3W2gwd.out (No such file or directory)

编辑:正如Mark根据XCode指出的那样,必须为每个架构单独构建预编译头,所以我的问题是,如果有任何方法让gcc在构建通用对象时使用正确的预编译头.

我确实意识到我可以像XCode一样完全分离构建每个架构,但我更愿意利用同时构建它们的可能性,而不必使用不同的构建配置.

Answer 1

我刚刚遇到了同样的问题，并跟进了 @lucas 提供的链接，所以我想我会提供我在这里找到的内容。

首先要注意的是，如果您将 gcc 代码从 Linux 移植到 MacOS，Apple 提供的 gcc 版本无法正确检测 .hpp 文件扩展名。

mac:openstudio lefticus$ g++ test.hpp
ld: warning: ignoring file test.hpp, file was built for unsupported file format which is not the architecture being linked (x86_64)
Undefined symbols for architecture x86_64:
  "_main", referenced from:
      start in crt1.10.6.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

正如另一个答案中提到的，最好指定-x参数以确保 gcc 知道您正在编译的文件类型。

g++ -x c++-header test.hpp

这将创建预期的test.hpp.gch.

您可以在命令行上指定任何体系结构，并且 gch 会正确构建

g++ -x c++-header test.hpp -arch i386

或者

g++ -x c++-header test.hpp -arch x86_64

如果您提供多个架构，您会收到发帖人提到的错误。

mac:openstudio lefticus$ g++ -xc++-header test.hpp -arch i386 -arch x86_64
Undefined symbols for architecture i386:
  "_main", referenced from:
      start in crt1.10.6.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status
Undefined symbols for architecture x86_64:
  "_main", referenced from:
      start in crt1.10.6.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
lipo: can't open input file: /var/folders/DM/DMTpbjzHHX08IEqGgEAORE+++TI/-Tmp-//ccDeWigf.out (No such file or directory)

关键是单独编译您需要的架构，然后-Xarch_在编译期间使用参数加载适当的架构：

g++ -x c++-header -arch x86_64 x86_64/test.hpp
g++ -x c++-header -arch i386 i386/test.hpp

g++ -arch i386 -arch x86_64 test.cpp -Xarch_i386 -Ii386 -Xarch_x86_64 -Ix86_64