CheckStructHasMember

This module provides a command to check whether a struct or class has a specified member variable.

在 CMake 專案中使用以下命令載入該模組：

include(CheckStructHasMember)

命令

This module provides the following command:

check_struct_has_member

Checks once if the given struct or class has the specified member variable:

check_struct_has_member(
  <struct>
  <member>
  <headers>
  <variable>
  [LANGUAGE <language>]
)

This command checks once whether the struct or class <struct> contains the specified <member> after including the given header(s) <headers> where the prototype should be declared. Multiple header files can be specified in one argument as a string using a semicolon-separated list. The result is stored in an internal cache variable <variable>.

選項有：

LANGUAGE <language>

Use the <language> compiler to perform the check. Acceptable values are C and CXX. If not specified, it defaults to C.

影響檢查的變數

可以在呼叫此命令之前設定以下變數，以修改檢查的執行方式：

CMAKE_REQUIRED_FLAGS

一個以空格分隔的字串，包含要傳遞給編譯器的額外旗標。分號分隔列表將無法運作。CMAKE_<LANG>_FLAGS 及其關聯的特定組態 CMAKE_<LANG>_FLAGS_<CONFIG> 變數的內容會在該變數的內容之前自動預置到編譯器命令中。

CMAKE_REQUIRED_DEFINITIONS

一個編譯器定義的分號分隔列表，每個定義的形式為 -DFOO 或 -DFOO=bar。由檢查命令的結果變數引數所指定的名稱的定義也會自動新增。

CMAKE_REQUIRED_INCLUDES

一個要傳遞給編譯器的標頭搜尋路徑的分號分隔列表。這些將是唯一使用的標頭搜尋路徑；INCLUDE_DIRECTORIES 目錄屬性的內容將被忽略。

CMAKE_REQUIRED_LINK_OPTIONS

在 3.14 版被加入.

一個要新增到連結命令的選項的分號分隔列表（詳情請參見 try_compile()）。

CMAKE_REQUIRED_LIBRARIES

一個要新增到連結命令的程式庫的分號分隔列表。這些可以是系統程式庫的名稱，也可以是 Imported Targets`（詳情請參見 :command:`try_compile）。

CMAKE_REQUIRED_LINK_DIRECTORIES

在 3.31 版被加入.

一個要傳遞給連結器的程式庫搜尋路徑的分號分隔列表（詳情請參見 try_compile()）。

CMAKE_REQUIRED_QUIET

在 3.1 版被加入.

如果此變數的值為布林真值，則與檢查相關的所有狀態訊息都將被抑制。

範例

Example: Checking C Struct Member

In the following example, this module checks if the C struct timeval has a member variable tv_sec after including the <sys/select.h> header. The result of the check is stored in the internal cache variable HAVE_TIMEVAL_TV_SEC.

include(CheckStructHasMember)

check_struct_has_member(
  "struct timeval"
  tv_sec
  sys/select.h
  HAVE_TIMEVAL_TV_SEC
)

Example: Checking C++ Struct Member

In the following example, this module checks if the C++ struct std::tm has a member variable tm_gmtoff after including the <ctime> header. The result of the check is stored in the internal cache variable HAVE_TM_GMTOFF.

include(CheckStructHasMember)

check_struct_has_member(
  std::tm
  tm_gmtoff
  ctime
  HAVE_TM_GMTOFF
  LANGUAGE CXX
)

Example: Isolated Check With Compile Definitions

In the following example, the check is performed with temporarily modified compile definitions using the CMakePushCheckState module:

include(CheckStructHasMember)
include(CMakePushCheckState)

cmake_push_check_state(RESET)
  set(CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)

  check_struct_has_member(
    "struct utsname"
    domainname
    sys/utsname.h
    HAVE_UTSNAME_DOMAINNAME
  )
cmake_pop_check_state()