macOS 10.13: `missing cmath members` while building llvm

[cglong]

Issue

When building from source using Homebrew on macOS 10.13, I receive a bunch of errors like the following:

In file included from /tmp/rust-20210815-3759-45jmpa/rustc-1.53.0-src/src/llvm-project/llvm/lib/Support/APFloat.cpp:14:
In file included from /tmp/rust-20210815-3759-45jmpa/rustc-1.53.0-src/src/llvm-project/llvm/include/llvm/ADT/APFloat.h:19:
In file included from /tmp/rust-20210815-3759-45jmpa/rustc-1.53.0-src/src/llvm-project/llvm/include/llvm/ADT/APInt.h:19:
In file included from /tmp/rust-20210815-3759-45jmpa/rustc-1.53.0-src/src/llvm-project/llvm/include/llvm/Support/MathExtras.h:20:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cmath:316:9: error: no member named 'isinf' in the global namespace
using ::isinf;
      ~~^

The full error stack is available here: 02.make.log

Version it worked on

It most recently worked on: 1.51.0

Version with regression

1.53.0 (1.52.0 failed as well, but I haven't verified for sure that it's the same issue)

---

Apologies there's not more detail here, I'm pretty new to Rust 🙂 I'll be happy to help investigate this further however possible!

[jyn514]

This looks like the C++ toolchain on your host is broken - can you compile a normal C++ program that has #include <cmath>?

Either way this is unlikely to be a Rust bug, this happens while building LLVM.

[cglong]

Thank you @jyn514! I'll try a simple program for this. FWIW though, someone on Stack Overflow faced this same issue so I think this isn't local to my system. Quoting their investigation since it has more details:

The easiest solution seems to be to uninstall the Command Line Tools, which works on Catalina, but I was hitting this on High Sierra, where I resorted to editing /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cmath

to comment out #include <math.h> and replace it with:

#include</Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/math.h>

I had to do this to get homebrew's Rust (rustc-1.53.0) to compile on High Sierra. Probably a better approach would be to tell cmake:

set(CMAKE_OSX_SYSROOT /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk)

since it's not usually a great idea to mess with the system-supplied headers.

[cglong]

I just verified that this program builds and runs successfully:

#include <cmath>

int main() {
    return 0;
}

[jyn514]

That stackoverflow answer looks right, I would try some of the things suggested there: https://stackoverflow.com/a/58670035.

Again, this is unlikely to be a Rust bug, so if nothing there works, consider reporting this upstream to LLVM.

[cglong]

Got it, I'll try these steps! I'll reopen this if the LLVM team believes this might actually be a Rust bug 🙂 Thank you for the fast reply @jyn514!

[jiezhoucs]

I just verified that this program builds and runs successfully:

#include <cmath>

int main() {
    return 0;
}

I just tried on the latest MacOS (11.5.2) and including <cmath> in a plain hello world cpp program triggers those no member named xxx errors.

[cglong]

I've created an upstream bug about this!

[jyn514]

the conclusion of this story is: if you really must set your own system include paths using -isystem, that is fine, but you must also set the C++ include paths correctly, and in the right order, not only the plain C include paths.

I'll check the Rust build system to see if I can find out where these flags are being set

@cglong try looking around src/bootstrap/native.rs

[cglong]

Thank you @jyn514! Really appreciate you reading through the LLVM ticket and letting me know where to start 😊