When linking mostly-static Linux binaries, link libstdc++.a explicitly.

This allows libstdc++ to be statically linked, which is normally only
possible when invoking GCC as `g++` with the `-static-libstdc++` flag.

Fixes #2840

See envoyproxy/envoy#415 for additional
background and context.

cc @htuch (for Envoy) and @calpeyser @hlopko (who I talked to earlier about this)

I'm only doing this in the Linux toolchain because MacOS doesn't do static linking of system libs anyway, and I don't know enough about Windows or FreeBSD to test on those platforms.

Closes #4031.

PiperOrigin-RevId: 178762357

src/test/shell/bazel/BUILD

@@ -374,6 +374,13 @@ sh_test(
     data = [":test-deps"],
 )
 
+sh_test(
+    name = "cc_static_binary_test",
+    size = "medium",
+    srcs = ["cc_static_binary_test.sh"],
+    data = [":test-deps"],
+)
+
 sh_test(
     name = "bazel_sandboxing_test",
     size = "large",

src/test/shell/bazel/cc_static_binary_test.sh

@@ -0,0 +1,89 @@
+#!/bin/bash
+#
+# Copyright 2017 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Tests for Bazel's static linking of C++ binaries.
+
+CURRENT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${CURRENT_DIR}/../integration_test_setup.sh" \
+  || { echo "integration_test_setup.sh not found!" >&2; exit 1; }
+
+if ! is_linux; then
+  echo "Tests for cc_binary static linking currently only run in Linux (this platform is ${PLATFORM})" >&2
+  exit 0
+fi
+
+function set_up() {
+  mkdir -p cpp/static
+  cat > cpp/static/main.cc <<EOF
+#include <iostream>
+int main() {
+  std::cout << "hello world!\n";
+  return 0;
+}
+EOF
+}
+
+function test_linux_somewhat_static_cc_binary() {
+  cat > cpp/static/BUILD <<EOF
+cc_binary(
+  name = "somewhat-static",
+  srcs = ["main.cc"],
+  linkstatic = 1,
+)
+EOF
+  assert_build //cpp/static:somewhat-static
+}
+
+function test_linux_mostly_static_cc_binary() {
+  cat > cpp/static/BUILD <<EOF
+cc_binary(
+  name = "mostly-static",
+  srcs = ["main.cc"],
+  linkstatic = 1,
+  linkopts = [
+    "-static-libstdc++",
+    "-static-libgcc",
+  ],
+)
+EOF
+  assert_build //cpp/static:mostly-static
+  LDD_STDOUT=$(ldd bazel-bin/cpp/static/mostly-static)
+  if [[ "${LDD_STDOUT}" =~ "libstdc++" ]]; then
+    log_fatal "A mostly-static binary shouldn't dynamically link libstdc++"
+  fi
+}
+
+function test_linux_fully_static_cc_binary() {
+  cat > cpp/static/BUILD <<EOF
+cc_binary(
+  name = "fully-static",
+  srcs = ["main.cc"],
+  linkstatic = 1,
+  linkopts = [
+    "-static",
+    "-static-libstdc++",
+    "-static-libgcc",
+  ],
+)
+EOF
+  assert_build //cpp/static:fully-static
+  LDD_STDOUT=$(ldd bazel-bin/cpp/static/fully-static || true)
+  if [[ ! "${LDD_STDOUT}" =~ "not a dynamic executable" ]]; then
+    log_fatal "Expected a fully-static binary"
+  fi
+}
+
+run_suite "static cc_binary"

src/test/shell/testenv.sh

@@ -30,6 +30,10 @@ function is_darwin() {
   [[ "${PLATFORM}" =~ darwin ]]
 }
 
+function is_linux() {
+  [[ "${PLATFORM}" =~ linux ]]
+}
+
 function _log_base() {
   prefix=$1
   shift

tools/cpp/CROSSTOOL.tpl

@@ -129,6 +129,7 @@ toolchain {
 %{opt_content}
   }
   linking_mode_flags { mode: DYNAMIC }
+%{link_content}
 
 %{coverage}
 

tools/cpp/unix_cc_configure.bzl

@@ -46,6 +46,29 @@ def _build_crosstool(d, prefix="  "):
   return "\n".join(lines)
 
 
+def _build_link_content():
+  # `-static-libstdc++` is only supported when invoking GCC as `g++`, and
+  # `-lstdc++` forces dynamic linking of libstdc++. To get desired
+  # mostly-static behavior, invoke the link by explicitly naming a static
+  # library archive.
+  #
+  # https://github.com/bazelbuild/bazel/issues/2840
+  return """
+  linking_mode_flags {
+    mode: DYNAMIC
+    linker_flag: "-lstdc++"
+  }
+  linking_mode_flags {
+    mode: FULLY_STATIC
+    linker_flag: "-lstdc++"
+  }
+  linking_mode_flags {
+    mode: MOSTLY_STATIC
+    linker_flag: "-l:libstdc++.a"
+  }
+  """
+
+
 def _build_tool_path(d):
   """Build the list of %-escaped tool_path for the CROSSTOOL file."""
   lines = []
@@ -174,7 +197,6 @@ def _crosstool_content(repository_ctx, cc, cpu_value, darwin):
           "-std=c++0x",
       ] + _escaped_cplus_include_paths(repository_ctx),
       "linker_flag": [
-          "-lstdc++",
           "-lm",  # Some systems expect -lm in addition to -lstdc++
           # Anticipated future default.
       ] + (
@@ -385,6 +407,7 @@ def configure_unix_toolchain(repository_ctx, cpu_value):
                     _build_tool_path(tool_paths),
       "%{opt_content}": _build_crosstool(opt_content, "    "),
       "%{dbg_content}": _build_crosstool(dbg_content, "    "),
+      "%{link_content}": _build_link_content(),
       "%{cxx_builtin_include_directory}": "",
       "%{coverage}": _coverage_feature(darwin),
       "%{msvc_env_tmp}": "",

tools/cpp/windows_cc_configure.bzl

@@ -313,6 +313,7 @@ def configure_windows_toolchain(repository_ctx):
         "%{content}": _get_escaped_windows_msys_crosstool_content(repository_ctx),
         "%{opt_content}": "",
         "%{dbg_content}": "",
+        "%{link_content}": "",
         "%{cxx_builtin_include_directory}": "",
         "%{coverage}": "",
     })