nocompile.gni

# Copyright 2011 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# This file is meant to be included into an target to create a unittest that
# invokes a set of no-compile tests.  A no-compile test is a test that asserts
# a particular construct will not compile.
#
# Usage:
#
# 1. Create a GN target:
#
#    import("//build/nocompile.gni")
#
#    nocompile_source_set("base_nocompile") {
#      sources = [
#        "functional/one_not_equal_two_nocompile.nc",
#      ]
#      deps = [
#        ":base"
#      ]
#    }
#
#    Note that by convention, nocompile tests use the `.nc` extension rather
#    than the standard `.cc` extension: this is because the expectation lines
#    often exceed 80 characters, which would make clang-format unhappy.
#
# 2. Add a dep from a related test binary to the nocompile source set:
#
#    test("base_unittests") {
#      ...
#      deps += [ ":base_nocompile_tests" ]
#    }
#
# 3. Populate the .nc file with test cases. Expected compile failures should be
#    annotated with a comment of the form:
#
#    // expected-error {{<expected error string here>}}
#
#    For example:
#
#    void OneDoesNotEqualTwo() {
#      static_assert(1 == 2);  // expected-error {{static assertion failed due to requirement '1 == 2'}}
#    }
#
#    The verification logic is built as part of clang; full documentation is at
#    https://clang.llvm.org/doxygen/classclang_1_1VerifyDiagnosticConsumer.html.
#
# Also see:
#   http://dev.chromium.org/developers/testing/no-compile-tests
#
import("//build/config/clang/clang.gni")
if (is_win) {
  import("//build/toolchain/win/win_toolchain_data.gni")
}

declare_args() {
  enable_nocompile_tests = (is_linux || is_chromeos || is_apple || is_win) &&
                           is_clang && host_cpu == target_cpu
  enable_nocompile_tests_new = is_clang && !is_nacl
}

if (enable_nocompile_tests_new) {
  template("nocompile_source_set") {
    action_foreach(target_name) {
      testonly = true

      script = "//tools/nocompile/wrapper.py"
      sources = invoker.sources
      deps = invoker.deps

      # An action is not a compiler, so configs is empty until it is explicitly set.
      configs = default_compiler_configs

      # Disable the checks that the Chrome style plugin normally enforces to
      # reduce the amount of boilerplate needed in nocompile tests.
      configs -= [ "//build/config/clang:find_bad_constructs" ]

      if (is_win) {
        result_path =
            "$target_out_dir/$target_name/{{source_name_part}}_placeholder.obj"
      } else {
        result_path =
            "$target_out_dir/$target_name/{{source_name_part}}_placeholder.o"
      }
      rebased_obj_path = rebase_path(result_path, root_build_dir)

      depfile = "${result_path}.d"
      rebased_depfile_path = rebase_path(depfile, root_build_dir)
      outputs = [ result_path ]

      if (is_win) {
        if (host_os == "win") {
          cxx = "clang-cl.exe"
        } else {
          cxx = "clang-cl"
        }
      } else {
        cxx = "clang++"
      }

      args = []

      if (is_win) {
        # ninja normally parses /showIncludes output, but the depsformat
        # variable can only be set in compiler tools, not for custom actions.
        # Unfortunately, this means the clang wrapper needs to generate the
        # depfile itself.
        args += [ "--generate-depfile" ]
      }

      args += [
        rebase_path("$clang_base_path/bin/$cxx", root_build_dir),
        "{{source}}",
        rebased_obj_path,
        rebased_depfile_path,
        "--",
        "{{cflags}}",
        "{{cflags_cc}}",
        "{{defines}}",
        "{{include_dirs}}",

        # No need to generate an object file for nocompile tests.
        "-Xclang",
        "-fsyntax-only",

        # Enable clang's VerifyDiagnosticConsumer:
        # https://clang.llvm.org/doxygen/classclang_1_1VerifyDiagnosticConsumer.html
        "-Xclang",
        "-verify",

        # But don't require expected-note comments since that is not the
        # primary point of the nocompile tests.
        "-Xclang",
        "-verify-ignore-unexpected=note",

        # Disable the error limit so that nocompile tests do not need to be
        # arbitrarily split up when they hit the default error limit.
        "-ferror-limit=0",

        # So funny characters don't show up in error messages.
        "-fno-color-diagnostics",

        # Always treat warnings as errors.
        "-Werror",
      ]

      if (!is_win) {
        args += [
          # On non-Windows platforms, clang can generate the depfile.
          "-MMD",
          "-MF",
          rebased_depfile_path,
          "-MT",
          rebased_obj_path,

          # Non-Windows clang uses file extensions to determine how to treat
          # various inputs, so explicitly tell it to treat all inputs (even
          # those with weird extensions like .nc) as C++ source files.
          "-x",
          "c++",
        ]
      } else {
        # For some reason, the Windows includes are not part of the default
        # compiler configs. Set it explicitly here, since things like libc++
        # depend on the VC runtime.
        if (target_cpu == "x86") {
          win_toolchain_data = win_toolchain_data_x86
        } else if (target_cpu == "x64") {
          win_toolchain_data = win_toolchain_data_x64
        } else if (target_cpu == "arm64") {
          win_toolchain_data = win_toolchain_data_arm64
        } else {
          error("Unsupported target_cpu, add it to win_toolchain_data.gni")
        }
        args += win_toolchain_data.include_flags_imsvc_list
        args += [ "/showIncludes:user" ]
      }

      # Note: for all platforms, the depfile only lists user includes, and not
      # system includes. If system includes change, the compiler flags are
      # expected to artificially change in some way to invalidate and force the
      # nocompile tests to run again.
    }
  }
}

# TODO(https://crbug.com/1480969): this section remains for legacy
# documentation. However, nocompile tests using these legacy templates are
# migrated to the new-style tests. Please do not add more old-style tests.
#
# To use this, create a GN target with the following form:
#
# import("//build/nocompile.gni")
# nocompile_test("my_module_nc_unittests") {
#   sources = [
#     'nc_testset_1.nc',
#     'nc_testset_2.nc',
#   ]
#
#   # optional extra include dirs:
#   include_dirs = [ ... ]
# }
#
# The tests are invoked by building the target named in the nocompile_test()
# macro, for example:
#
# ninja -C out/Default my_module_nc_unittests
#
# The .nc files are C++ files that contain code we wish to assert will not
# compile. Each individual test case in the file should be put in its own
# #if defined(...) section specifying an unique preprocessor symbol beginning
# with NCTEST which names the test. The set of tests in a file is automatically
# determined by scanning the file for these #if blocks and no other explicit
# definition of the symbol is required to register a test.
#
# The expected complier error message should be appended with a C++-style
# comment that has a python list of regular expressions. This will likely be
# greater than 80-characters. Giving a solid expected output test is important
# so that random compile failures do not cause the test to pass.
#
# Example .nc file:
#
#   #if defined(NCTEST_NEEDS_SEMICOLON)  // [r"expected ',' or ';' at end of input"]
#
#   int a = 1
#
#   #elif defined(NCTEST_NEEDS_CAST)  // [r"invalid conversion from 'void*' to 'char*'"]
#
#   void* a = NULL;
#   char* b = a;
#
#   #endif
#
# If we need to disable NCTEST_NEEDS_SEMICOLON, then change the #if to:
#
#   #if defined(DISABLED_NCTEST_NEEDS_SEMICOLON)
#   ...
#   #elif defined(NCTEST_NEEDS_CAST)
#   ...
#
# The lines above are parsed by a regexp so avoid getting creative with the
# formatting or ifdef logic; it will likely just not work.
#
# Implementation notes:
# The .nc files are actually processed by a python script which executes the
# compiler and generates a .cc file that is empty on success, or will have a
# series of #error lines on failure, and a set of trivially passing gunit
# TEST() functions on success. This allows us to fail at the compile step when
# something goes wrong, and know during the unittest run that the test was at
# least processed when things go right.

if (enable_nocompile_tests) {
  import("//build/config/c++/c++.gni")
  import("//build/config/sysroot.gni")
  import("//testing/test.gni")

  if (is_mac) {
    import("//build/config/mac/mac_sdk.gni")
  }

  template("nocompile_test") {
    nocompile_target = target_name + "_run_nocompile"

    action_foreach(nocompile_target) {
      testonly = true
      script = "//tools/nocompile/driver.py"
      sources = invoker.sources
      deps = invoker.deps
      if (defined(invoker.public_deps)) {
        public_deps = invoker.public_deps
      }

      result_path = "$target_gen_dir/{{source_name_part}}_nc.cc"
      outputs = [ result_path ]
      rebased_result_path = rebase_path(result_path, root_build_dir)
      if (is_win) {
        if (host_os == "win") {
          cxx = "clang-cl.exe"
          nulldevice = "nul"
        } else {
          cxx = "clang-cl"

          # Unfortunately, clang-cl always wants to suffix the output file name
          # with ".obj", and /dev/null.obj is not a valid file. As a bit of a
          # hack, simply use the path to the generated .cc file, knowing:
          # - that clang-cl will append ".obj" to the filename, so it will never
          #   clash.
          # - except when the nocompile test unexpectedly passes, the output
          #   file will never actually be written.
          nulldevice = rebased_result_path
        }
      } else {
        cxx = "clang++"
      }

      depfile = "${result_path}.d"

      args = []
      if (is_win) {
        args += [
          "--depfile",
          rebased_result_path + ".d",
        ]
      }
      args += [
        rebase_path("$clang_base_path/bin/$cxx", root_build_dir),
        "4",  # number of compilers to invoke in parallel.
        "{{source}}",
        rebased_result_path,
        "--",
        "-Werror",
        "-Wfatal-errors",
        "-Wthread-safety",
        "-I" + rebase_path("//", root_build_dir),
        "-I" + rebase_path("//third_party/abseil-cpp/", root_build_dir),
        "-I" + rebase_path("//buildtools/third_party/libc++/", root_build_dir),
        "-I" + rebase_path(root_gen_dir, root_build_dir),

        # TODO(https://crbug.com/989932): Track build/config/compiler/BUILD.gn
        "-Wno-implicit-int-float-conversion",
      ]
      if (is_win) {
        # On Windows we fall back to using system headers from a sysroot from
        # depot_tools. This is negotiated by python scripts and the result is
        # available in //build/toolchain/win/win_toolchain_data.gni. From there
        # we get the `include_flags_imsvc` which point to the system headers.
        if (host_cpu == "x86") {
          win_toolchain_data = win_toolchain_data_x86
        } else if (host_cpu == "x64") {
          win_toolchain_data = win_toolchain_data_x64
        } else if (host_cpu == "arm64") {
          win_toolchain_data = win_toolchain_data_arm64
        } else {
          error("Unsupported host_cpu, add it to win_toolchain_data.gni")
        }
        args += win_toolchain_data.include_flags_imsvc_list

        args += [
          "/W4",
          "-Wno-unused-parameter",
          "-I" + rebase_path("$libcxx_prefix/include", root_build_dir),
          "/std:c++20",
          "/showIncludes",
          "/Fo" + nulldevice,
          "/c",
          "/Tp",
        ]
      } else {
        args += [
          "-Wall",
          "-nostdinc++",
          "-isystem" + rebase_path("$libcxx_prefix/include", root_build_dir),
          "-isystem" + rebase_path("$libcxxabi_prefix/include", root_build_dir),
          "-std=c++20",
          "-MMD",
          "-MF",
          rebased_result_path + ".d",
          "-MT",
          rebased_result_path,
          "-o",
          "/dev/null",
          "-c",
          "-x",
          "c++",
        ]
      }
      args += [ "{{source}}" ]

      if (is_mac && host_os != "mac") {
        args += [
          "--target=x86_64-apple-macos",
          "-mmacos-version-min=$mac_deployment_target",
        ]
      }

      # Iterate over any extra include dirs and append them to the command line.
      if (defined(invoker.include_dirs)) {
        foreach(include_dir, invoker.include_dirs) {
          args += [ "-I" + rebase_path(include_dir, root_build_dir) ]
        }
      }

      if (sysroot != "") {
        assert(!is_win)
        sysroot_path = rebase_path(sysroot, root_build_dir)
        args += [
          "--sysroot",
          sysroot_path,
        ]
      }

      if (!is_nacl) {
        args += [
          # TODO(crbug.com/1343975) Evaluate and possibly enable.
          "-Wno-deprecated-builtins",
        ]
      }
    }

    test(target_name) {
      deps = invoker.deps + [ ":$nocompile_target" ]
      sources = get_target_outputs(":$nocompile_target")
      forward_variables_from(invoker, [ "bundle_deps" ])
    }
  }
}