External Issue: driver.cpp build failures on Apple Clang (version range TBD)

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17860, "PHHargrove", "driver.cpp build failures on Apple Clang (version range TBD)", "2021-05-29T21:45:01Z"

Since May 28 when commit e7de784 on master was tested, our nightly CI of GASNet + Chapel has been failing to compile driver.cpp with old Apple Xcode 9.2 compilers: Apple LLVM version 9.0.0 (clang-900.0.39.2) . The previous test (successful) of this target was almost one week earlier: May 22 on commit 1f3bfc5 .

Our CI rotation has not attempted Xcode newer than 9.2 since this was first observed. I will update this issue as soon as I have data for something newer (hopefully I get an off-cycle run in later today). IFF this turns out to be an issue only with this ancient compiler, I'll be fine if you want to simply disclaim support for it (I believe Apple already has).

I believe this is, in part, due the use of -Werror in our builds with CHPL_COMM_DEBUG=1 CHPL_DEVELOPER=1

In file included from driver.cpp:51:
In file included from ../next/include/chpl/queries/Context.h:23:
In file included from ../next/include/chpl/queries/Context-detail.h:23:
In file included from ../next/include/chpl/queries/ErrorMessage.h:23:
In file included from ../next/include/chpl/queries/Location.h:23:
In file included from ../next/include/chpl/queries/UniqueString.h:28:
../next/include/chpl/queries/UniqueString-detail.h:119:16: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
      return { nullptr };
               ^~~~~~~
               {      }
../next/include/chpl/queries/UniqueString-detail.h:129:16: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
      return { (const char*) val };
               ^~~~~~~~~~~~~~~~~
               {                }
../next/include/chpl/queries/UniqueString-detail.h:133:14: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
    return { s };
             ^
             {}
3 errors generated.

Full output from our first observation of this issue is available here, but is slightly muddled by make -j4.