support selectively disabling NS_BLOCK_ASSERTIONS for opt builds (#341)

maintains the default behavior of passing `-DNS_BLOCK_ASSERTIONS=1` for
opt builds. for builds where this is undesirable, set
`--features=-ns_block_assertions` to unconditionally not-set this flag,
without having to unset the entire `default_compile_flags` feature.

crosstool/cc_toolchain_config.bzl

@@ -2077,7 +2077,6 @@ please file an issue at https://github.com/bazelbuild/apple_support/issues/new
  "-g0",
  "-O2",
  "-DNDEBUG",
- "-DNS_BLOCK_ASSERTIONS=1",
  ],
  ),
  ],
@@ -2116,6 +2115,31 @@ please file an issue at https://github.com/bazelbuild/apple_support/issues/new
  ],
  )
 
+ ns_block_assertions_feature = feature(
+ name = "ns_block_assertions",
+ enabled = True,
+ flag_sets = [
+ flag_set(
+ actions = [
+ ACTION_NAMES.assemble,
+ ACTION_NAMES.preprocess_assemble,
+ ACTION_NAMES.linkstamp_compile,
+ ACTION_NAMES.c_compile,
+ ACTION_NAMES.cpp_compile,
+ ACTION_NAMES.cpp_header_parsing,
+ ACTION_NAMES.cpp_module_compile,
+ ACTION_NAMES.cpp_module_codegen,
+ ACTION_NAMES.lto_backend,
+ ACTION_NAMES.clif_match,
+ ACTION_NAMES.objc_compile,
+ ACTION_NAMES.objcpp_compile,
+ ],
+ flag_groups = [flag_group(flags = ["-DNS_BLOCK_ASSERTIONS=1"])],
+ with_features = [with_feature_set(features = ["opt"])],
+ ),
+ ],
+ )
+
  objcopy_embed_flags_feature = feature(
  name = "objcopy_embed_flags",
  enabled = True,
@@ -2656,6 +2680,7 @@ please file an issue at https://github.com/bazelbuild/apple_support/issues/new
  # Features with more configuration
  link_libcpp_feature,
  default_compile_flags_feature,
+ ns_block_assertions_feature,
  debug_prefix_map_pwd_is_dot_feature,
  remap_xcode_path_feature,
  generate_dsym_file_feature,

test/compiling_tests.bzl

@@ -7,6 +7,21 @@ load(
 
 default_test = make_action_command_line_test_rule()
 
+opt_test = make_action_command_line_test_rule(
+ config_settings = {
+ "//command_line_option:compilation_mode": "opt",
+ },
+)
+
+disable_ns_block_assertions_feature_test = make_action_command_line_test_rule(
+ config_settings = {
+ "//command_line_option:compilation_mode": "opt",
+ "//command_line_option:features": [
+ "-ns_block_assertions",
+ ],
+ },
+)
+
 def compiling_test_suite(name):
  """Tests for compilation behavior.
 
@@ -26,6 +41,30 @@ def compiling_test_suite(name):
  target_under_test = "//test/test_data:cc_main",
  )
 
+ opt_test(
+ name = "{}_opt_link_test".format(name),
+ tags = [name],
+ expected_argv = [
+ "-DNDEBUG",
+ "-DNS_BLOCK_ASSERTIONS=1",
+ ],
+ mnemonic = "CppCompile",
+ target_under_test = "//test/test_data:cc_main",
+ )
+
+ disable_ns_block_assertions_feature_test(
+ name = "{}_disable_ns_block_assertions_feature_test".format(name),
+ tags = [name],
+ expected_argv = [
+ "-DNDEBUG",
+ ],
+ not_expected_argv = [
+ "-DNS_BLOCK_ASSERTIONS=1",
+ ],
+ mnemonic = "CppCompile",
+ target_under_test = "//test/test_data:cc_main",
+ )
+
  native.test_suite(
  name = name,
  tags = [name],