CODEWITHSUNDEEP
c++macoslibc++darwin
Engineerist
Engineerist

Reputation: 367

Mac OSX libc++ is missing std::uncaught_exceptions symbol

I noticed that std::uncaught_exceptions symbol is missing from the stock libc++ on my Mac:

$ clang++ -v; otool -L /usr/lib/libc++.dylib
Apple LLVM version 7.3.0 (clang-703.0.31)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
/usr/lib/libc++.dylib:
    /usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 120.1.0)
    /usr/lib/libc++abi.dylib (compatibility version 1.0.0, current version 125.0.0)
...
$ nm /usr/lib/libc++.dylib | c++filt | grep uncaught
0000000000007782 T std::uncaught_exception()
                 U ___cxa_uncaught_exception

However, the header declares the prototype:

$ pwd
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1
$ grep uncaught_exceptions exception
int  uncaught_exceptions() noexcept;  // C++17
_LIBCPP_FUNC_VIS int uncaught_exceptions() _NOEXCEPT;

Is this a bad build or something? From the libc++ source I see that the symbol should end up in libc++ but it's not there and I get a missing symbol when linking.

Edit: here is a minimal failing program:

$ cat t.cpp; clang++ -std=c++1z t.cpp
#include <exception>

int main () {
    return std::uncaught_exceptions ();
}
Undefined symbols for architecture x86_64:
  "std::uncaught_exceptions()", referenced from:
      _main in t-a4015f.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Upvotes: 1

Views: 1481

Answers (1)

Howard Hinnant
Howard Hinnant

Reputation: 219205

It has been a while (couple years) since Apple thought it important enough to update libc++.dylib. I hear rumors it might be updated in the OS after El Capitan.

What's wrong with Swift?! ;-)

Upvotes: 2

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