work around SR-11680

[mayoff]

The Swift bug report: https://bugs.swift.org/browse/SR-11680

Swift nightly toolchains are available here: https://swift.org/download/

The Swift nightly toolchains cannot build OpenCombine. Here's why:

1. The COpenCombineHelpers target defines a non-static function
   (opencombine_stop_in_debugger) in a header file. This function is
   emitted in the target's IR, but not in the target's TBD.

2. Swift nightly toolchains have assertions enabled, so they use the
   -validate-tbd-against-ir=missing build setting. This build setting
   makes the compiler fail if the TBD doesn't match the IR.

This commit turns off the build setting for the OpenCombine target.

[MaxDesiatov]

The linked SR-11680 has different environment specified, namely Xcode 11.0, swift-5.1-RELEASE. Does that mean that using nightlies is not required to reproduce it?

[broadwaylamb]

Hi @mayoff, thanks for pointing out this issue!

However, we can't use the unsafeFlags in a public target because of this:

As some build flags can be exploited for unsupported or malicious behavior, a product can’t be used as a dependency in another package if one of its targets uses unsafe flags.

So, basically, clients won't be able to depend on OpenCombine.

What I would suggest to do is simply define opencombine_stop_in_debugger out of line in COpenCombineHelpers.cpp instead of the header file.

[codecov]

Codecov Report

Merging #145 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #145      +/-   ##
==========================================
+ Coverage   98.24%   98.29%   +0.05%     
==========================================
  Files          84       82       -2     
  Lines        4730     4639      -91     
==========================================
- Hits         4647     4560      -87     
+ Misses         83       79       -4

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[OpenCombineBot]

LGTM

Generated by 🚫 Danger Swift against c44eda4

[mayoff]

@MaxDesiatov I don't know if the RELEASE builds at https://swift.org/download/ are built with assertions. You could (I assume) trigger the same error by manually setting-validate-tbd-against-ir=missing with any toolchain.

@broadwaylamb Oh, good point. I'll revise the patch to non-inline the function.

[broadwaylamb]

Nice!

[mayoff]

I have rewritten the patch so that it no longer uses .unsafeFlags.