CheckTypeSize¶
Check sizeof a type
- CHECK_TYPE_SIZE¶
CHECK_TYPE_SIZE(TYPE VARIABLE [BUILTIN_TYPES_ONLY] [LANGUAGE <language>])
Check if the type exists and determine its size. On return,
HAVE_${VARIABLE}holds the existence of the type, and${VARIABLE}holds one of the following:<size> = type has non-zero size <size> "0" = type has arch-dependent size (see below) "" = type does not exist
Both
HAVE_${VARIABLE}and${VARIABLE}will be created as internal cache variables.Furthermore, the variable
${VARIABLE}_CODEholds C preprocessor code to define the macro${VARIABLE}to the size of the type, or leave the macro undefined if the type does not exist.The variable
${VARIABLE}may be0whenCMAKE_OSX_ARCHITECTUREShas multiple architectures for building OS X universal binaries. This indicates that the type size varies across architectures. In this case${VARIABLE}_CODEcontains C preprocessor tests mapping from each architecture macro to the corresponding type size. The list of architecture macros is stored in${VARIABLE}_KEYS, and the value for each key is stored in${VARIABLE}-${KEY}.If the
BUILTIN_TYPES_ONLYoption is not given, the macro checks for headers<sys/types.h>,<stdint.h>, and<stddef.h>, and saves results inHAVE_SYS_TYPES_H,HAVE_STDINT_H, andHAVE_STDDEF_H. The type size check automatically includes the available headers, thus supporting checks of types defined in the headers.If
LANGUAGEis set, the specified compiler will be used to perform the check. Acceptable values areCandCXX.
Despite the name of the macro you may use it to check the size of more complex expressions, too. To check e.g. for the size of a struct member you can do something like this:
check_type_size("((struct something*)0)->member" SIZEOF_MEMBER)
The following variables may be set before calling this macro to modify the way the check is run:
CMAKE_REQUIRED_FLAGSstring of compile command line flags.
CMAKE_REQUIRED_DEFINITIONSlist of macros to define (-DFOO=bar).
CMAKE_REQUIRED_INCLUDESlist of include directories.
CMAKE_REQUIRED_LINK_OPTIONSNew in version 3.14: list of options to pass to link command.
CMAKE_REQUIRED_LIBRARIESlist of libraries to link.
CMAKE_REQUIRED_QUIETNew in version 3.1: execute quietly without messages.
CMAKE_EXTRA_INCLUDE_FILESlist of extra headers to include.