Question

# If the user hasn't told use specifically what they want, build only
# a static library.

IF(NOT DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC)
   SET(PODOFO_BUILD_STATIC TRUE)
   SET(PODOFO_BUILD_SHARED FALSE)
ENDIF(NOT DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC)

IF(DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC)
    SET(PODOFO_BUILD_SHARED NOT ${PODOFO_BUILD_SHARED})
ENDIF(DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC)

IF(NOT DEFINED PODOFO_BUILD_SHARED AND DEFINED PODOFO_BUILD_STATIC)
    SET(PODOFO_BUILD_SHARED NOT ${PODOFO_BUILD_STATIC})
ENDIF(NOT DEFINED PODOFO_BUILD_SHARED AND DEFINED PODOFO_BUILD_STATIC)

“SET（PODOFO_BUILD_SHARED NOT $ {PODOFO_BUILD_SHARED}）”是什么意思？在那些片段之前，我看不到任何PODOFO_BUILD_SHARED变量的定义

Answer 1

前4行采用2“布尔”变量PODOFO_BUILD_STATIC和PODOFO_BUILD_SHARED，如果两者都没有定义，则将它们设置为默认值
如果仅定义PODOFO_BUILD_SHARED，则无论其初始值是什么，第二行反转PODOFO_BUILD_SHARED的值。的怪异！

最后3行采用PODOFO_BUILD_STATIC的反转值，如果仅定义了PODOFO_BUILD_STATIC，则将其分配给PODOFO_BUILD_SHARED

然而，整体行为似乎有点奇怪。我的猜测就是这个（后三行）：

IF(DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC) SET(PODOFO_BUILD_SHARED NOT ${PODOFO_BUILD_SHARED}) ENDIF(DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC)

应该是：

IF(DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC) SET(PODOFO_BUILD_STATIC NOT ${PODOFO_BUILD_SHARED}) ENDIF(DEFINED PODOFO_BUILD_SHARED AND NOT DEFINED PODOFO_BUILD_STATIC)

通过这种方式，它更有意义：如果只定义了2个变量中的一个，则将另一个设置为相反的值。

“SET（PODOFO_BUILD_SHARED NOT $ {PODOFO_BUILD_SHARED}）”是什么意思？在那些片段之前，我看不到任何PODOFO_BUILD_SHARED变量的定义

可以通过多种方式预先在文件外部定义变量（例如，从命令行，或通过cmake-gui设置缓存变量）

CMake：“SET（PODOFO_BUILD_SHARED NOT $ {PODOFO_BUILD_SHARED}）”是什么意思？

1 个答案: