[libcxx-commits] [libcxx] [libc++] Fixes lit portability issues. (PR #72435)

[Louis Dionne via libcxx-commits]

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@@ -29,7 +29,13 @@ def appendToSubstitution(substitutions, key, value):
     return [(k, v + " " + value) if k == key else (k, v) for (k, v) in substitutions]
 
 
-std = getSubstitution("%{cxx_std}", config)
+# External users of the LLVM test suite might not have set the substitutions.
+std = ""
+try:
+    std = getSubstitution("%{cxx_std}", config)
+except:
+    pass
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ldionne wrote:

This substitution definitely should be provided by whoever runs the test suite -- it's defined in `params.py`. Is there something I misunderstand here?

The rest of the changes look fine, but this one seems like guarding against something we don't support and should never happen.

https://github.com/llvm/llvm-project/pull/72435