Add the cxx_* targets for libc++

The following targets will be added to deal with the libc++ standard
library:

 - libcxx_static
 - libcxx_shared
 - libcxx_copy_shared
 - libcxx_abi_static
 - libcxx_abi_shared
 - libcxx_copy_abi_shared

The 'libcxx' prefix can be configured in the 'WORKSPACE' file using the
'libcxx_prefix' optional parameter of the 'llvm_configure' repository
rule.

To protect adding of the targets as dependencies, a number of macroses
are put into the 'llvm_config.bzl' generated file: the `if_cxx_linked`
function that evaluated its first argument when the local LLVM
installation is linked against libc++ and 'llvm_cxx_copts' array that
contains the `-stdlib=libc++` compiler option in this case.

Signed-off-by: Pavel Samolysov <samolisov@gmail.com>

README.md

@@ -52,16 +52,17 @@ llvm_configure(
     name = "local_llvm",
     llvm_prefix = "llvm_",
     clang_prefix = "clang_",
+    libcxx_prefix = "libcxx_",
     add_headers_to_deps = False,
 )
 ```
 
-Where `name` is whatever you want, default values for `llvm_prefix` and `clang_prefix`
-may be omitted. By default, the header libraries will be automatically included as dependency
-to the generated targets (the LLVM header library to LLVM's, Clang's and other project's
-targets, the Clang header library to Clang's targets, etc.) If you would like to manually
-put the header libraries to dependencies, set up the `add_headers_to_deps` attribute of the
-reporitory rule to `False`.
+Where `name` is whatever you want, default values for `llvm_prefix`, `clang_prefix` and
+`libcxx_prefix` may be omitted. By default, the header libraries will be automatically
+included as dependency to the generated targets (the LLVM header library to LLVM's, Clang's
+and other project's targets, the Clang header library to Clang's targets, etc.) If you would
+like to manually put the header libraries to dependencies, set up the `add_headers_to_deps`
+attribute of the reporitory rule to `False`.
 
 There are three ways to use the library: the first, primarily, is shown
 above: the LLVM libraries are fetched from a local installation so the `LLVM_INSTALL_PREFIX`
@@ -77,6 +78,7 @@ llvm_configure(
     name = "local_llvm",
     llvm_prefix = "llvm_",
     clang_prefix = "clang_",
+    libcxx_prefix = "libcxx_",
     sha256 = "ec5d7fd082137ce5b72c7b4dde9a83c07a7e298773351ab6a0693a8200d0fa0c",
     strip_prefix = "clang+llvm-8.0.1-x86_64-linux-sles11.3",
     urls = [
@@ -98,6 +100,7 @@ llvm_configure(
     name = "local_llvm",
     llvm_prefix = "llvm_",
     clang_prefix = "clang_",
+    libcxx_prefix = "libcxx_",
     build_file = "//:llvm.autogenerated.BUILD",
     config_file = "//:llvm_config.bzl",
     sha256 = "345dcab760b0e13f1df1b57efa0651dbaae300187bc1556379b562b85bec9e11",
@@ -145,7 +148,10 @@ cc_binary(
     deps = [
         "@local_llvm//:llvm_headers",
         "@local_llvm//:llvm_bit_reader",
-    ],
+    ] + if_cxx_linked([
+        "@local_llvm//:libcxx_shared",
+        "@local_llvm//:libcxx_abi_shared",
+    ]),
     visibility = ["//visibility:private"],
 )
 ```
@@ -251,3 +257,45 @@ a rule and it will appear in
 a `bazel-bin/external/<name of llvm_configure repository rule>`
 directory. Then the library can be copied into the `bazel-bin` (see the
 genrule in the BUILD file) and be used for running your applications.
+
+### Linking against the libc++ standard library
+
+Archives hosted on the http://releases.llvm.org/download.html official website,
+usually are built against the 'libc++' standard library. A number of Starlark
+macroses and pre-defined arrays are developed to deal with the 'libc++' standard
+library and can be loaded from the generated `llvm_config.bzl` file. The `if_cxx_linked`
+function is used to safely add the `libcxx_static/libcxx_shared` and
+`libcxx_abi_static/libcxx_abi_shared` targets as dependencies. The first argument
+of the function will be taken into account when the local LLVM installation
+is linked against 'libc++', otherwise the second one (optional) will be used.
+
+The `-stdlib=libc++` compiler option can be added as the `llvm_cxx_copts` array.
+If 'libc++' is not used, the array will just be empty, so that the array
+should not be wrapped in the `if_cxx_linked` function.
+
+There is an example how to use the `libcxx_*` targets and options:
+
+```bzl
+llvm_copts = select({
+    ":linux_x86_64": llvm_nix_copts + llvm_cxx_copts,
+    ":macos_x86_64": llvm_nix_copts + llvm_cxx_copts,
+    ":windows_x86_64": llvm_win_copts,
+    "//conditions:default": [],
+})
+
+cc_binary(
+    name = 'llvm_bb_counter',
+    srcs = [
+        "llvm/llvm_bb_counter.cc",
+    ],
+    copts = llvm_copts,
+    deps = [
+        "@local_llvm//:llvm_headers",
+        "@local_llvm//:llvm_bit_reader",
+    ] + if_cxx_linked([
+        "@local_llvm//:libcxx_static",      # if you prefer shared libraries,
+        "@local_llvm//:libcxx_abi_static",  # use libcxx_shared and libcxx_abi_shared
+    ]),
+    visibility = ["//visibility:private"],
+)
+```

examples/BUILD

@@ -32,6 +32,8 @@ config_setting(
 load("@local_llvm//:llvm_config.bzl",
     "llvm_nix_copts",
     "llvm_win_copts",
+    "llvm_cxx_copts",
+    "if_cxx_linked",
     "if_has_aarch64",
     "if_has_amdgpu",
     "if_has_arm",
@@ -48,21 +50,26 @@ load("@local_llvm//:llvm_config.bzl",
     "if_has_x86",
     "if_has_x_core")
 
+llvm_copts = select({
+    ":linux_x86_64": llvm_nix_copts + llvm_cxx_copts,
+    ":macos_x86_64": llvm_nix_copts + llvm_cxx_copts,
+    ":windows_x86_64": llvm_win_copts,
+    "//conditions:default": [],
+})
+
 cc_binary(
     name = 'llvm_bb_counter',
     srcs = [
         "llvm/llvm_bb_counter.cc",
     ],
-    copts = select({
-        ":linux_x86_64": llvm_nix_copts,
-        ":macos_x86_64": llvm_nix_copts,
-        ":windows_x86_64": llvm_win_copts,
-        "//conditions:default": [],
-    }),
+    copts = llvm_copts,
     deps = [
         "@local_llvm//:headers",
         "@local_llvm//:bit_reader",
-    ],
+    ] + if_cxx_linked([
+        "@local_llvm//:cxx_static",
+        "@local_llvm//:cxx_abi_static",
+    ]),
     visibility = ["//visibility:private"],
 )
 
@@ -71,12 +78,7 @@ cc_library(
     srcs = [
         "llvm/function_argument_usage_pass.cc",
     ],
-    copts = select({
-        ":linux_x86_64": llvm_nix_copts,
-        ":macos_x86_64": llvm_nix_copts,
-        ":windows_x86_64": llvm_win_copts,
-        "//conditions:default": [],
-    }),
+    copts = llvm_copts,
     deps = [
         "@local_llvm//:headers",
         "@local_llvm//:core",
@@ -93,7 +95,10 @@ cc_binary(
     ],
     deps = [
         ":llvm_exp_passes",
-    ],
+    ] + if_cxx_linked([
+        "@local_llvm//:cxx_shared",
+        "@local_llvm//:cxx_abi_shared",
+    ]),
     visibility = ["//visibility:private"],
 )
 
@@ -102,12 +107,7 @@ cc_binary(
     srcs = [
         "llvm/llvm_print_supported_targets.cc",
     ],
-    copts = select({
-        ":linux_x86_64": llvm_nix_copts,
-        ":macos_x86_64": llvm_nix_copts,
-        ":windows_x86_64": llvm_win_copts,
-        "//conditions:default": [],
-    }),
+    copts = llvm_copts,
     defines = if_has_aarch64(["LLVM_SUPPORTS_TARGET_AARCH64"])
         + if_has_amdgpu(["LLVM_SUPPORTS_TARGET_AMDGPU"])
         + if_has_arm(["LLVM_SUPPORTS_TARGET_ARM"])
@@ -194,20 +194,18 @@ cc_binary(
         "@local_llvm//:x_core_asm_printer",
         "@local_llvm//:x_core_code_gen",
         "@local_llvm//:x_core_disassembler",
-    ])
+    ]) + if_cxx_linked([
+        "@local_llvm//:cxx_shared",
+        "@local_llvm//:cxx_abi_shared",
+    ]),
 )
 
 cc_binary(
     name = 'clang_list_methods',
     srcs = [
         "clang/clang_list_methods.cc",
     ],
-    copts = select({
-        ":linux_x86_64": llvm_nix_copts,
-        ":macos_x86_64": llvm_nix_copts,
-        ":windows_x86_64": llvm_win_copts,
-        "//conditions:default": [],
-    }),
+    copts = llvm_copts,
     data = select({
         ":linux_x86_64": [
             "copy_local_llvm_shared_lin",
@@ -226,7 +224,10 @@ cc_binary(
         "@local_llvm//:config_headers",
         "@local_llvm//:headers",
         "@local_llvm//:support",
-    ],
+    ] + if_cxx_linked([
+        "@local_llvm//:cxx_shared",
+        "@local_llvm//:cxx_abi_shared",
+    ]),
     linkopts = select({
         ":linux_x86_64": [
             "-Wl,-R -Wl,."

examples/WORKSPACE

@@ -15,6 +15,7 @@ llvm_configure(
     name = "local_llvm",
     llvm_prefix = "",            # default value: llvm_
     clang_prefix = "cl_",        # default value: clang_
+    libcxx_prefix = "cxx_",      # default value: libcxx_
     add_headers_to_deps = False, # default value: True
 
     # Either the LLVM_INSTALL_PREFIX environment variable must point to

llvm/BUILD.tpl

@@ -186,3 +186,10 @@ exports_files(["LICENSE.TXT"])
 %{LLVM_CONFIG_GENRULE}
 %{LLVM_CONFIG_LIB}
 %{DEP_LIBS}
+
+%{LIBCXX_STATIC_LIB}
+%{LIBCXX_SHARED_LIB}
+%{LIBCXX_SHARED_COPY_GENRULE}
+%{LIBCXX_ABI_STATIC_LIB}
+%{LIBCXX_ABI_SHARED_LIB}
+%{LIBCXX_ABI_SHARED_COPY_GENRULE}

llvm/llvm_config.bzl.tpl

@@ -9,6 +9,16 @@ llvm_win_copts is a convenient set of platform-dependent compiler options
 to enable the building process of LLVM-dependent targets for Windows platform.
 It can disable RTTI and enable the right level of C++.
 
+llvm_cxx_copts is a convenient set of "libc++" specific compiler options.
+May be used to enable "libc++" as a standard library for the build.
+
+llvm_cxx_linked is a flag that displays if LLVM is linked against the "libc++"
+standard library.
+
+if_cxx_linked is a conditional to check if the LLVM installation
+is built against the "libc++" standard library. If so, the first argument
+will be returned, otherwise the second one.
+
 llvm_targets is a list of supported targets ("AArch64", "ARM", "X86", etc.)
 
 if_has_<TARGET> is a conditional to check if we are building with the target
@@ -27,6 +37,15 @@ llvm_targets = [
 %{LLVM_TARGETS}
 ]
 
+llvm_cxx_linked = %{LLVM_CXX_LINKED}
+
+llvm_cxx_copts = [
+    %{LLVM_CXX_COPT}
+]
+
+def if_cxx_linked(if_true, if_false = []):
+    return if_true if llvm_cxx_linked else if_false
+
 def if_has_aarch64(if_true, if_false = []):
     return if_true if "AArch64" in llvm_targets else if_false
 

llvm/llvm_configure.bzl

@@ -368,10 +368,9 @@ def _llvm_get_rule_name(
         'prefix_dict'.
     """
     concat_format = "%s%s"
-    if name.startswith("llvm_"):
-        return concat_format % (prefix_dict["llvm"], name[len("llvm_"):])
-    if name.startswith("clang_"):
-        return concat_format % (prefix_dict["clang"], name[len("clang_"):])
+    for old_prefix, new_prefix in prefix_dict.items():
+        if name.startswith(old_prefix):
+            return concat_format % (new_prefix, name[len(old_prefix) + 1:])
     return name
 
 def _llvm_get_rule_names(
@@ -787,6 +786,29 @@ def _llvm_local_enabled(repository_ctx):
         ]))
     return enabled
 
+def _llvm_is_linked_against_cxx(repository_ctx, directory = "lib"):
+    """Returns whether the LLVM installation is linked against the libc++
+       standard library.
+
+    Args:
+        repository_ctx: the repository_ctx object.
+        directory: where to search the libc++ files, 'lib' by default.
+    Returns:
+        True if any of the libc++ binaries presents in the
+        local LLVM installation, False otherwise.
+    """
+    library_files_params = [
+        _static_library_file_params(repository_ctx),
+        _import_library_file_params(repository_ctx)
+    ]
+
+    for library_prefix, library_ext in library_files_params:
+        libcxx_file = "%s/%s%s.%s" % (directory, library_prefix, "c++", library_ext)
+        if repository_ctx.path(libcxx_file).exists:
+            return True
+
+    return False
+
 def _llvm_get_install_path(repository_ctx):
     """Returns a path to a local LLVM installation passed in
        the '_LLVM_INSTALL_PREFIX' environment variable.
@@ -842,6 +864,7 @@ def _llvm_installed_impl(repository_ctx):
     prefix_dictionary = {
         "llvm": repository_ctx.attr.llvm_prefix,
         "clang": repository_ctx.attr.clang_prefix,
+        "libcxx": repository_ctx.attr.libcxx_prefix,
     }
     # if there are duplicated prefixes, fail.
     _llvm_check_duplicated_prefixes(prefix_dictionary)
@@ -1907,6 +1930,23 @@ def _llvm_installed_impl(repository_ctx):
         "%{LLVM_CONFIG_LIB}":
             _llvm_get_config_library_rule(ctx, prx, "llvm_config_headers",
                 "llvm_config_files", "generated/include"),
+
+        "%{LIBCXX_STATIC_LIB}":
+            _llvm_get_library_rule(ctx, prx, "libcxx_static", "c++"),
+        "%{LIBCXX_SHARED_LIB}":
+            _llvm_get_shared_library_rule(ctx, prx, "libcxx_shared", "c++"),
+        "%{LIBCXX_SHARED_COPY_GENRULE}":
+            _llvm_get_shared_lib_genrule(ctx, prx, "libcxx_copy_shared",
+                llvm_path, "c++"),
+        "%{LIBCXX_ABI_STATIC_LIB}":
+            _llvm_get_library_rule(ctx, prx, "libcxx_abi_static", "c++abi"),
+        "%{LIBCXX_ABI_SHARED_LIB}":
+            _llvm_get_shared_library_rule(ctx, prx, "libcxx_abi_shared",
+                "c++abi"),
+        "%{LIBCXX_ABI_SHARED_COPY_GENRULE}":
+            _llvm_get_shared_lib_genrule(ctx, prx, "libcxx_copy_abi_shared",
+                llvm_path, "c++abi"),
+
         "%{DEP_LIBS}":
             "\n".join([_llvm_get_shared_library_rule(ctx, prx, dep_name, dep_name,
                             ignore_prefix = True, directory = dep_name)
@@ -1919,6 +1959,9 @@ def _llvm_installed_impl(repository_ctx):
     _tpl(repository_ctx, "llvm_config.bzl", {
         "%{LLVM_TARGETS}": _llvm_get_formatted_target_list(repository_ctx,
             supported_targets),
+        "%{LLVM_CXX_LINKED}": str(_llvm_is_linked_against_cxx(repository_ctx)),
+        "%{LLVM_CXX_COPT}": "\"-stdlib=libc++\"" if _llvm_is_linked_against_cxx(
+            repository_ctx) else "",
     })
 
 llvm_configure = repository_rule(
@@ -1931,6 +1974,7 @@ llvm_configure = repository_rule(
         "strip_prefix": attr.string(default = ""),
         "llvm_prefix": attr.string(default = "llvm_"),
         "clang_prefix": attr.string(default = "clang_"),
+        "libcxx_prefix": attr.string(default = "libcxx_"),
         "add_headers_to_deps": attr.bool(default = True),
     },
     environ = [