[GHC] #16083: tests relying on <iostream> in Objective C++ are broken on Mojave builder (was: objcpp-hi test appears to be broken on Mojave builder)

[GHC]

#16083: tests relying on <iostream> in Objective C++ are broken on Mojave builder
---------------------------------+--------------------------------------
        Reporter:  bgamari       |                Owner:  (none)
            Type:  bug           |               Status:  new
        Priority:  normal        |            Milestone:
       Component:  Compiler      |              Version:  8.6.3
      Resolution:                |             Keywords:
Operating System:  MacOS X       |         Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):
       Wiki Page:                |
---------------------------------+--------------------------------------

Old description:

> It appears that something has changed in the Darwin toolchain such that
> `<iostream>` is no longer found by default:
> {{{
> cd "driver/recomp001/recomp001.run" && $MAKE -s --no-print-directory
> recomp001
> Compile failed (exit code 1) errors were:
> warning: include path for stdlibc++ headers not found; pass '-std=libc++'
> on the command line to use the libc++ standard library instead
> [-Wstdlibcxx-not-found]
>
> objcpp-hi.mm:2:9: error:  fatal error: 'iostream' file not found
> #import <iostream>
>         ^~~~~~~~~~
> 1 warning and 1 error generated.
> `gcc' failed in phase `C Compiler'. (Exit code: 1)
>
> *** unexpected failure for objcpp-hi(normal)
> }}}
>
> Marking as broken.

New description:

 It appears that something has changed in the Darwin toolchain such that
 `<iostream>` is no longer found by default:
 {{{
 cd "driver/recomp001/recomp001.run" && $MAKE -s --no-print-directory
 recomp001
 Compile failed (exit code 1) errors were:
 warning: include path for stdlibc++ headers not found; pass '-std=libc++'
 on the command line to use the libc++ standard library instead
 [-Wstdlibcxx-not-found]

 objcpp-hi.mm:2:9: error:  fatal error: 'iostream' file not found
 #import <iostream>
         ^~~~~~~~~~
 1 warning and 1 error generated.
 `gcc' failed in phase `C Compiler'. (Exit code: 1)

 *** unexpected failure for objcpp-hi(normal)

 Compile failed (exit code 1) errors were:
 warning: include path for stdlibc++ headers not found; pass '-std=libc++'
 on the command line to use the libc++ standard library instead
 [-Wstdlibcxx-not-found]

 /var/folders/pb/c3dc08v12yzc536lnrnngvd40000gq/T/ghc56064_0/ghc_2.cpp:1:10:
 error:
      fatal error: 'iostream' file not found
 #include <iostream>
          ^~~~~~~~~~
 1 warning and 1 error generated.
 `gcc' failed in phase `C Compiler'. (Exit code: 1)

 *** unexpected failure for T13366(normal)
 }}}

 Marking as broken.

--

Comment (by bgamari):

 `T13366` is also affected.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16083#comment:1>
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