Merge pull request #20698 from mppf/remove-homebrew-workaround

Remove workaround for Homebrew libc++ issue

This PR removes a workaround for issue #19217 (which is the same issue as
Homebrew/homebrew-core#96915 and
llvm/llvm-project#54438 ).

The problem is solved in the current Homebrew LLVM 14 and LLVM 15
formulae now that libc++ is installed into a different directory than the
LLVM libraries. (This problem would still be present for the LLVM 12 and
13 formulae). Since the workaround is removed, this PR adjusts
printchplenv to raise an error if using Mac OS X with system LLVM 11, 12,
or 13. Such LLVMs will not be selected as a quickstart configuration.
Also, it updates prereqs.rst to indicate that LLVM 14 or newer is
required on Mac OS X.

Reviewed by @daviditen - thanks!

- [x] testing on Mac OS X 10.15 "Catalina"
- [x] testing on Mac OS X 11 "Big Sur"
- [x] testing on Mac OS X 12 "Monterey" (x86)
- [x] testing on Mac OS X 12 "Monterey" (M1)

doc/rst/usingchapel/prereqs.rst

@@ -36,9 +36,10 @@ for using Chapel:
 
   * CMake is available and ``cmake`` runs version 3.13.4 or later.
 
-  * The LLVM backend is now the default and it is easiest to use it with
-    a system-wide installation of LLVM. LLVM and clang versions 11, 12,
-    13 and 14 are currently supported. If a system-wide installation of
+  * The LLVM backend is now the default and it is easiest to use it with a
+    system-wide installation of LLVM and clang. On Mac OS X, only LLVM 14 is
+    supported. On other platforms, LLVM and clang versions 11, 12, 13 and 14
+    are currently supported. If a system-wide installation of
     LLVM and clang with one of those versions is not available, you can
     use the bundled LLVM or disable LLVM support (see
     :ref:`readme-chplenv.CHPL_LLVM`).

util/chplenv/chpl_llvm.py

@@ -172,6 +172,29 @@ def check_llvm_packages(llvm_config):
         s = "Could not find the clang library {0}".format(clang_cpp_lib)
         s += "\nPerhaps you need to install the libclang-cpp-dev package"
 
+    host_platform = chpl_platform.get('host')
+    if host_platform == "darwin":
+        # on Mac OS X with Homebrew, require LLVM 14 or newer
+        # because these LLVM versions fix a problem with
+        # mixing libc++ versions
+        llvm_version, ignored_err = check_llvm_config(llvm_config)
+        llvm_version = llvm_version.strip()
+        bad_vers = ('11', '12', '13')
+        if llvm_version in bad_vers:
+            # compute the set subtraction:
+            #    llvm_versions() - bad_vers
+            # for use in the error message
+            ok_vers = [ ]
+            vers = llvm_versions()
+            for v in vers:
+                if not v in bad_vers:
+                    ok_vers.append(v)
+
+            s = ("LLVM version {0} is not supported on Mac OS X. "
+                 "Please use one of these versions: {1}"
+                 .format(llvm_version, ', '.join(ok_vers)))
+
+
     return (s == '', s)
 
 
@@ -588,32 +611,6 @@ def get_system_llvm_built_sdkroot():
                             return path
     return None
 
-# Returns True if the workaround for issue #19217 should be applied
-# and False otherwise.
-# That workaround adds the Mac OS X system libc++ before the linker
-# search paths so that the system libc++ is used rather than a
-# libc++ that came with the system install of LLVM (e.g. from Homebrew).
-# Whether or not to try the workaround can be controlled by the variable
-#  CHPL_HOST_USE_SYSTEM_LIBCXX
-@memoize
-def use_system_libcxx_workaround():
-    host_platform = chpl_platform.get('host')
-    if host_platform == "darwin":
-        # If the variable for this is set to something other that '0' or 'no'
-        # then do the workaround.
-        # This variable exists to support building the Homebrew formula
-        # from source because during that build, `brew` is not available.
-        override_var = overrides.get('CHPL_HOST_USE_SYSTEM_LIBCXX', '')
-        if override_var != '':
-            return (override_var != "0" and override_var != "no")
-
-        # otherwise, do the workaround if we detect homebrew
-        homebrew_prefix = chpl_platform.get_homebrew_prefix()
-
-        if homebrew_prefix:
-            return True
-
-    return False
 
 # On some systems, we need to give clang some arguments for it to
 # find the correct system headers.
@@ -782,15 +779,6 @@ def get_host_compile_args():
         return (bundled, system)
 
     if llvm_support_val == 'system':
-        # On Mac OS X with Homebrew, apply a workaround for issue #19217.
-        # This avoids finding headers in the libc++ installed by llvm@12 e.g.
-        if use_system_libcxx_workaround():
-            sdkroot = get_system_llvm_built_sdkroot()
-            if sdkroot:
-                system.append("-isysroot")
-                system.append(sdkroot)
-                system.append("-I" + os.path.join(sdkroot, "usr", "include"))
-
         # Ubuntu 16.04 needed -fno-rtti for LLVM 3.7
         # tested on that system after installing
         #   llvm-3.7-dev llvm-3.7 clang-3.7 libclang-3.7-dev libedit-dev
@@ -861,16 +849,6 @@ def get_host_link_args():
         llvm_components = ['support']
 
     if llvm_support_val == 'system':
-        # On Mac OS X with Homebrew, apply a workaround for issue #19217.
-        # This avoids linking with the libc++ installed by llvm@12 e.g.
-        if use_system_libcxx_workaround():
-            sdkroot = get_system_llvm_built_sdkroot()
-            if sdkroot:
-                # Note: -isysroot only affects includes
-                # and -Wl,-syslibroot seems to have no effect
-                system.append("-L" + os.path.join(sdkroot, "usr", "lib"))
-
-
         # For LLVM version 11 and older, there was a problem where
         # 'llvm-config' did not work properly on Mac OS X, so work around
         # that by using static linking.