[libc][bazel] Prevent LIBC_NAMESPACE leakeage (#70455)

Right now `LIBC_NAMESPACE` definition is added to all rules that depend on any libc function. This have far-reaching effects which prevents llvm-libc development when the installed libc is itself llvm-libc.

This PR removes the `:libc_root` target entirely and consistently uses the provided libc BUILD actions for compilation and testing. This makes sure that we don't leak `LIBC_NAMESPACE` to our clients.

Author: gchatelet

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

@@ -4,43 +4,56 @@
 
 """LLVM libc starlark rules for building individual functions."""
 
+load("@bazel_skylib//lib:paths.bzl", "paths")
 load("@bazel_skylib//lib:selects.bzl", "selects")
+load(":libc_namespace.bzl", "LIBC_NAMESPACE")
 load(":platforms.bzl", "PLATFORM_CPU_ARM64", "PLATFORM_CPU_X86_64")
 
-LIBC_ROOT_TARGET = ":libc_root"
-INTERNAL_SUFFIX = ".__internal__"
+def libc_internal_target(name):
+    return name + ".__internal__"
 
-def _libc_library(name, copts = None, **kwargs):
+def libc_common_copts():
+    root_label = Label(":libc")
+    libc_include_path = paths.join(root_label.workspace_root, root_label.package)
+    return [
+        "-I" + libc_include_path,
+        "-DLIBC_NAMESPACE=" + LIBC_NAMESPACE,
+    ]
+
+def _libc_library(name, hidden, copts = [], deps = [], **kwargs):
     """Internal macro to serve as a base for all other libc library rules.
 
     Args:
       name: Target name.
       copts: The special compiler options for the target.
+      deps: The list of target dependencies if any.
+      hidden: Whether the symbols should be explicitly hidden or not.
       **kwargs: All other attributes relevant for the cc_library rule.
     """
-    copts = copts or []
 
     # We want all libc sources to be compiled with "hidden" visibility.
     # The public symbols will be given "default" visibility explicitly.
     # See src/__support/common.h for more information.
-    copts = copts + ["-fvisibility=hidden"]
+    if hidden:
+        copts = copts + ["-fvisibility=hidden"]
     native.cc_library(
         name = name,
-        copts = copts,
+        copts = copts + libc_common_copts(),
+        deps = deps,
         linkstatic = 1,
         **kwargs
     )
 
-# A convenience var which should be used to list all libc support libraries.
+# A convenience function which should be used to list all libc support libraries.
 # Any library which does not define a public function should be listed with
 # libc_support_library.
-libc_support_library = _libc_library
+def libc_support_library(name, **kwargs):
+    _libc_library(name = name, hidden = False, **kwargs)
 
 def libc_function(
         name,
         srcs,
         weak = False,
-        deps = None,
         copts = None,
         local_defines = None,
         **kwargs):
@@ -64,37 +77,33 @@ def libc_function(
                      its deps.
       **kwargs: Other attributes relevant for a cc_library. For example, deps.
     """
-    deps = deps or []
 
     # We use the explicit equals pattern here because append and += mutate the
     # original list, where this creates a new list and stores it in deps.
-    deps = deps + [LIBC_ROOT_TARGET]
     copts = copts or []
     copts = copts + ["-O3", "-fno-builtin", "-fno-lax-vector-conversions"]
 
     # We compile the code twice, the first target is suffixed with ".__internal__" and contains the
-    # C++ functions in the "__llvm_libc" namespace. This allows us to test the function in the
+    # C++ functions in the "LIBC_NAMESPACE" namespace. This allows us to test the function in the
     # presence of another libc.
-    native.cc_library(
-        name = name + INTERNAL_SUFFIX,
+    libc_support_library(
+        name = libc_internal_target(name),
         srcs = srcs,
-        deps = deps,
         copts = copts,
-        linkstatic = 1,
         **kwargs
     )
 
-    # This second target is the llvm libc C function.
-
+    # This second target is the llvm libc C function with either a default or hidden visibility.
+    # All other functions are hidden.
     func_attrs = ["__attribute__((visibility(\"default\")))"]
     if weak:
         func_attrs = func_attrs + ["__attribute__((weak))"]
     local_defines = local_defines or ["LIBC_COPT_PUBLIC_PACKAGING"]
     local_defines = local_defines + ["LLVM_LIBC_FUNCTION_ATTR='%s'" % " ".join(func_attrs)]
     _libc_library(
         name = name,
+        hidden = True,
         srcs = srcs,
-        deps = deps,
         copts = copts,
         local_defines = local_defines,
         **kwargs

utils/bazel/llvm-project-overlay/libc/libc_build_rules.bzl

@@ -4,11 +4,13 @@
 
 # LLVM libc unittest library.
 
+load("//libc:libc_build_rules.bzl", "libc_support_library")
+
 package(default_visibility = ["//visibility:public"])
 
 licenses(["notice"])
 
-cc_library(
+libc_support_library(
     name = "test_logger",
     srcs = ["TestLogger.cpp"],
     hdrs = ["TestLogger.h"],
@@ -17,11 +19,10 @@ cc_library(
         "//libc:__support_cpp_string_view",
         "//libc:__support_osutil_io",
         "//libc:__support_uint128",
-        "//libc:libc_root",
     ],
 )
 
-cc_library(
+libc_support_library(
     name = "LibcUnitTest",
     srcs = [
         "BazelFilePath.cpp",
@@ -52,12 +53,11 @@ cc_library(
         "//libc:__support_stringutil",
         "//libc:__support_uint128",
         "//libc:errno",
-        "//libc:libc_root",
         "//llvm:Support",
     ],
 )
 
-cc_library(
+libc_support_library(
     name = "fp_test_helpers",
     srcs = [
         "FPExceptMatcher.cpp",
@@ -79,11 +79,10 @@ cc_library(
         "//libc:__support_fputil_fp_bits",
         "//libc:__support_fputil_fpbits_str",
         "//libc:__support_fputil_rounding_mode",
-        "//libc:libc_root",
     ],
 )
 
-cc_library(
+libc_support_library(
     name = "memory_matcher",
     srcs = [
         "MemoryMatcher.cpp",
@@ -100,7 +99,7 @@ cc_library(
     ],
 )
 
-cc_library(
+libc_support_library(
     name = "printf_matcher",
     srcs = [
         "PrintfMatcher.cpp",
@@ -116,7 +115,7 @@ cc_library(
     ],
 )
 
-cc_library(
+libc_support_library(
     name = "string_utils",
     hdrs = [
         "StringUtils.h",

utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel

@@ -6,33 +6,34 @@
 
 libc functions are created though the libc_build_rules.bzl:libc_function.
 They come in two flavors:
- - the internal one that is scoped into the `__llvm_libc` namespace.
+ - the internal one that is scoped into the `LIBC_NAMESPACE` namespace.
  - the libc one that is the regular C function.
 
 When performing tests we make sure to always use the internal version.
 """
 
-load("//libc:libc_build_rules.bzl", "INTERNAL_SUFFIX")
+load("//libc:libc_build_rules.bzl", "libc_common_copts", "libc_internal_target")
 
-def libc_test(name, srcs, libc_function_deps, deps = [], **kwargs):
+def libc_test(name, srcs, libc_function_deps = [], copts = [], deps = [], **kwargs):
     """Add target for a libc test.
 
     Args:
       name: Test target name
       srcs: List of sources for the test.
       libc_function_deps: List of libc_function targets used by this test.
+      copts: The list of options to add to the C++ compilation command.
       deps: The list of other libraries to be linked in to the test target.
-      **kwargs: Attributes relevant for a cc_test. For example, name, srcs.
+      **kwargs: Attributes relevant for a libc_test. For example, name, srcs.
     """
     all_function_deps = libc_function_deps + ["//libc:errno"]
     native.cc_test(
         name = name,
         srcs = srcs,
-        deps = [d + INTERNAL_SUFFIX for d in all_function_deps] + [
-            "//libc:libc_root",
+        deps = [libc_internal_target(d) for d in all_function_deps] + [
             "//libc/test/UnitTest:LibcUnitTest",
         ] + deps,
         features = ["-link_llvmlibc"],  # Do not link libllvmlibc.a
+        copts = copts + libc_common_copts(),
         linkstatic = 1,
         **kwargs
     )

utils/bazel/llvm-project-overlay/libc/test/libc_test_rules.bzl

@@ -4,119 +4,83 @@
 
 # Tests for LLVM libc CPP functions.
 
+load("//libc/test:libc_test_rules.bzl", "libc_test")
+
 package(default_visibility = ["//visibility:public"])
 
 licenses(["notice"])
 
-cc_test(
+libc_test(
     name = "atomic_test",
     srcs = ["atomic_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_atomic",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_atomic"],
 )
 
-cc_test(
+libc_test(
     name = "bitset_test",
     srcs = ["bitset_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_bitset",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_bitset"],
 )
 
-cc_test(
+libc_test(
     name = "cstddef_test",
     srcs = ["cstddef_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_cstddef",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_cstddef"],
 )
 
-cc_test(
+libc_test(
     name = "integer_sequence_test",
     srcs = ["integer_sequence_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_utility",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_utility"],
 )
 
-cc_test(
+libc_test(
     name = "limits_test",
     srcs = ["limits_test.cpp"],
     deps = [
         "//libc:__support_cpp_limits",
         "//libc:__support_uint",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
     ],
 )
 
-cc_test(
+libc_test(
     name = "optional_test",
     srcs = ["optional_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_optional",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_optional"],
 )
 
-cc_test(
+libc_test(
     name = "span_test",
     srcs = ["span_test.cpp"],
     deps = [
         "//libc:__support_cpp_array",
         "//libc:__support_cpp_span",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
     ],
 )
 
-cc_test(
+libc_test(
     name = "stringstream_test",
     srcs = ["stringstream_test.cpp"],
     deps = [
         "//libc:__support_cpp_span",
         "//libc:__support_cpp_stringstream",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
     ],
 )
 
-cc_test(
+libc_test(
     name = "string_test",
     srcs = ["string_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_string",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_string"],
 )
 
-cc_test(
+libc_test(
     name = "stringview_test",
     srcs = ["stringview_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_string_view",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_string_view"],
 )
 
-cc_test(
+libc_test(
     name = "type_traits_test",
     srcs = ["type_traits_test.cpp"],
-    deps = [
-        "//libc:__support_cpp_type_traits",
-        "//libc:libc_root",
-        "//libc/test/UnitTest:LibcUnitTest",
-    ],
+    deps = ["//libc:__support_cpp_type_traits"],
 )