Spurious Warnings in Xcode 15

[bdkjones]

How frequently does the bug occur?

Always

Description

This may be related to #8251, but I recently added Realm to a project that I'm compiling with Xcode 15 beta 3 and I get 37 gobbledegook warnings about debug notes:

And I get a warning about duplicating the lc++ library:

(Nothing in this app uses C++ other than Realm.)

Stacktrace & log output

N/A

Can you reproduce the bug?

Always

Reproduction Steps

Include Realm in an app, then build it with Xcode 15 beta 3.

Version

10.40.2

What Atlas Services are you using?

Local Database only

Are you using encryption?

No

Platform OS and version(s)

macOS 13.4.1

Build environment

Xcode version: 15 beta 3
Dependency manager and version: SPM via Xcode

[dianaafanador3]

@bdkjones thanks for letting us know about this.
This issue appears since Xcode 15 beta and it's still happening on Xcode 15 beta 4, and by the looks of it seems like it is an Apple Bug. It seems like the linker is finding multiple occurrence of the same library, in concrete c++, and may be related to the introduction of C++ interoperability, but I'm not completely sure.
We'll keep this issue open so we can track any changes on future releases.

[dianaafanador3]

Some of this warnings have dissapeared on Xcode 15 Beta 5, the only one remaining is
Ignoring duplicate library '-lc++'.

[bdkjones]

@dianaafanador3 The remaining warning about duplicate C++ libraries still exists in Xcode 15 Beta 8.

The consensus is that since Apple added C++ interoperability (and therefore now link the C++ library by default) they forgot to handle all the many libraries that explicitly included the C++ libraries: getsentry/sentry-cocoa#3122 (comment)

I think this spurious warning is going to remain until Apple either gets their act together or Realm explicitly removes the C++ libraries when the build is done with Xcode 15+.

If it's possible for Realm to conditionally link the C++ libraries only for older Xcode releases, that would likely eliminate this last warning.

[vg-identance]

bump (Xcode 15 released and issue still exists)

[bdkjones]

This discussion explains the cause and a way for users to address it via a build flag:

https://indiestack.com/2023/10/xcode-15-duplicate-library-linker-warnings/

The following text should be added to "Other Linker Flags" in your Build Settings. Note: the text is one single entry and the spacing matters. You're passing this option through the compiler, down to the linker:

"-Wl,-no_warn_duplicate_libraries"

[bdkjones]

Closed the issue because the bug is Apple's and Realm can't solve it.