zircon/system/ulib/c/string/BUILD.gn

# Copyright 2023 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("../libc.gni")

llvm_libc_group("string") {
  deps = [
    ":compat",
    ":mem",
    ":str",
  ]

  # TODO(https://fxbug.dev/42053650): not yet using the llvm-libc versions of these
  non_test_deps = [
    "//zircon/third_party/ulib/musl/src/string:strerror_r",
    "//zircon/third_party/ulib/musl/src/string:strsignal",
    "//zircon/third_party/ulib/musl/src/string:strverscmp",
  ]

  # TODO(https://fxbug.dev/42053650): but run their tests in preparation
  testonly_deps = [ ":strsignalerror" ]
}

llvm_libc_source_set("mem") {
  functions = [
    "memccpy",
    "memmem",
    "mempcpy",
    "memrchr",
  ]

  deps = [
    ":memchr",
    ":memcmp",
    ":memcpy",
    ":memset",
  ]
}

unsanitized_funcs = [
  "memcpy",
  "memmove",
  "memset",
]

# The compiler will turn code that looks like it implements these functions
# into calls to their standard names.  It doesn't recognize that the internal
# implementation layers are going to be inlined into the public standard C
# function, so it just produces an infinite recursion (or a call via a PLT
# entry that hasn't been fixed up yet).  Using `-fno-builtin-FUNCTION` for the
# particular functions works around this.
foreach(funcs,
        [
          [ "memchr" ],
          [ "memcmp" ],
          [
            "memcpy",
            "memmove",
          ],
          [ "memset" ],
          [ "strlen" ],
        ]) {
  config("no-builtin-${funcs[0]}") {
    visibility = [ ":*" ]

    cflags = []

    # TODO(https://fxbug.dev/42079782): gcc is not correctly honoring -fno-builtin-memmove,
    # but -fno-builtin correctly suppresses the call to memmove.
    if (funcs[0] == "memcpy" && is_gcc) {
      cflags += [ "-fno-builtin" ]
    }

    foreach(func, funcs) {
      cflags += [ "-fno-builtin-$func" ]

      # TODO(https://fxbug.dev/42077425): The .weakref shenanigans in dynlink.c aren't
      # compatible with full LTO and a memcpy defined in C++. This only affects
      # riscv64 in practice, since others use assembly definitions regardless.
      if ((func == "memcpy" || func == "memset") && !is_gcc &&
          toolchain_environment == "user.basic") {
        cflags += [
          "-fno-lto",
          "-fno-whole-program-vtables",
        ]
      }
    }
  }

  llvm_libc_source_set(funcs[0]) {
    visibility = [ ":*" ]

    functions = funcs

    # Avoid self-referential libcalls.
    configs = [ ":no-builtin-${funcs[0]}" ]

    # These also need to stick to the basic machine ABI so that dynlink.c can
    # use them early.
    basic_abi = true

    non_test_vars = {
      # The user.basic environment doesn't export the symbols it defines.
      # When building for export in libc.so, we want these compiled in the
      # user.basic environment, but we also want to export names for them.  At
      # the same time, dynlink.c needs to use hidden symbols to access these
      # so that it won't use PLT entries before they're ready.  So compile
      # them using an override for the "src/__support/common.h" internal
      # header that redefines the implementation's LLVM_LIBC_FUNCTION macro to
      # add extra aliases.
      #
      # Note this is plumbed directly as include_dirs in the source_set() so
      # that it comes before all the include_dirs plumbs via configs.  If this
      # instead used non_test_deps to point at a group with public_configs
      # pointing at a config(), then those include_dirs would come after all
      # the ones from configs used to compile libc.  This needs to preempt
      # those, so it should come first as include_dirs et al directly in a
      # target like source_set() do.
      include_dirs = [ "mem-aliases-include" ]

      if (funcs + unsanitized_funcs - unsanitized_funcs != funcs) {
        defines = [ "LIBC_UNSANITIZED" ]
      }
    }
  }
}

# These are the functions that are nonproblematic in any context.
llvm_libc_source_set("minimal-str") {
  functions = [
    "stpcpy",
    "strchrnul",
    "strcpy",
    "strchr",
    "strspn",
    "strcat",
    "strstr",
    "strsep",
    "strcspn",
    "strncat",
    "strlcat",
    "strlcpy",
    "strncmp",
    "strrchr",
    "strncpy",
    "strcmp",
    "strnlen",
    "strpbrk",
    "stpncpy",
  ]

  deps = [
    ":mem",
    ":strlen",
  ]
}

llvm_libc_source_set("str") {
  functions = [
    "strcasecmp",
    "strcasestr",
    "strcoll",
    "strxfrm",
    "strdup",
    "strncasecmp",
    "strndup",
    "strtok",
    "strtok_r",

    # TODO(https://fxbug.dev/42053650): the llvm-libc versions of these are problematic
    #"strerror",
    #"strerror_r",
    #"strsignal",
  ]

  deps = [ ":minimal-str" ]
}

llvm_libc_source_set("strsignalerror") {
  visibility = [ ":*" ]

  functions = [
    "strerror",
    "strerror_r",
    "strsignal",
  ]

  deps = [ ":StringUtil" ]
}

llvm_libc_source_set("StringUtil") {
  visibility = [ ":*" ]

  dir = "__support/StringUtil"

  # This doesn't define any functions with tests of their own, but it's still
  # an llvm_libc_source_set() to get the dual production and testonly targets.
  # (There will also be an unused empty unittests subtarget.)
  functions = []

  public = [
    "error_to_string.h",
    "signal_to_string.h",
  ]
  sources = [
    "error_to_string.cpp",
    "message_mapper.h",
    "signal_to_string.cpp",
    "tables/linux_extension_errors.h",
    "tables/linux_extension_signals.h",
    "tables/linux_platform_errors.h",
    "tables/linux_platform_signals.h",
    "tables/minimal_platform_errors.h",
    "tables/minimal_platform_signals.h",
    "tables/posix_errors.h",
    "tables/posix_signals.h",
    "tables/signal_table.h",
    "tables/stdc_errors.h",
    "tables/stdc_signals.h",
  ]
}

llvm_libc_source_set("compat") {
  functions = [
    "bcmp",
    "bcopy",
    "bzero",
    "index",
    "rindex",
  ]

  deps = [ ":swab" ]
}

# This lives in libc/src/unistd upstream because it's declared in <unistd.h>
# but it's really a compat string function, so we include it here instead.
llvm_libc_source_set("swab") {
  dir = "unistd"
  functions = [ "swab" ]
}

# This provides an archive library of the universally safe string functions.
# When built outside the "user.libc" environment, these always define only
# hidden-visibility symbols and should be safe in any build environment.
static_library("hermetic") {
  complete_static_lib = true
  deps = [
    ":compat",
    ":minimal-str",
  ]
}