CheckSymbolExists

This module provides a command to check whether a C symbol exists.

在 CMake 專案中使用以下命令載入該模組：

include(CheckSymbolExists)

命令

This module provides the following command:

check_symbol_exists

Checks once whether a symbol exists as a function, variable, or preprocessor macro in C:

check_symbol_exists(<symbol> <headers> <variable>)

This command checks whether the <symbol> is available after including the specified header file(s) <headers>, and stores the result in the internal cache variable <variable>. Multiple header files can be specified in one argument as a string using a semicolon-separated list.

If the header files define the symbol as a macro, it is considered available and assumed to work. If the symbol is declared as a function or variable, the check also ensures that it links successfully (i.e., the symbol must exist in a linked library or object file). Compiler intrinsics may not be detected, as they are not always linkable or explicitly declared in headers.

Symbols that are types, enum values, or compiler intrinsics are not recognized. For those, consider using the CheckTypeSize or CheckSourceCompiles module instead.

This command is intended to check symbols as they appear in C. For C++ symbols, use the CheckCXXSymbolExists module instead.

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

The following example demonstrates how to check for the presence of a preprocessor macro SEEK_SET and the C function fopen() from the <stdio.h> header using this module:

include(CheckSymbolExists)

# Check for macro SEEK_SET
check_symbol_exists(SEEK_SET "stdio.h" HAVE_SEEK_SET)

# Check for function fopen
check_symbol_exists(fopen "stdio.h" HAVE_FOPEN)

另請參見