问题
I maintain a mixed C and C++ command line program that needs to run on Linux, Windows, and OS X. I recently upgraded to Yosemite and my OS X build is now failing. The error is:
/usr/include/dispatch/object.h:143:15: error: expected identifier or '(' before '^' token
Other folks have run into this bug.
The line of code that fails is a typedef that uses '^' which is a non-standard extension providing support for closures.
The underlying problem seems to be that some Apple standard headers are starting to require Clang specific extensions. Unfortunately our program has a very deep set of dependencies, some of which won't compile under Clang. We've been using the GCC compilers installed via MacPorts. I have a workaround for now: changing the line in the object.h header to be GCC compatible. However, hacking up the include files under /usr/include sounds to me like asking for trouble.
Can any OS X/Clang gurus suggest more sustainable ways of coping with this problem? Does this limit the future usefulness of GCC on OS X?
回答1:
Just for future visitors, the following should get most headers working with a recent GCC version:
In dispatch/object.h change
typedef void (^dispatch_block_t)(void);
to
#ifdef __clang__
typedef void (^dispatch_block_t)(void);
#else
typedef void* dispatch_block_t;
#endif
and in Availability.h change
#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
to
#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && defined(__clang__)
来源：https://stackoverflow.com/questions/27976312/how-to-cope-with-non-gcc-compatible-code-in-os-x-yosemite-core-headers