CheckTypeSize¶
Check sizeof a type
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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 be- 0when- CMAKE_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 in- HAVE_SYS_TYPES_H,- HAVE_STDINT_H, and- HAVE_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 are- Cand- CXX.
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_FLAGS = string of compile command line flags
CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
CMAKE_REQUIRED_INCLUDES = list of include directories
CMAKE_REQUIRED_LINK_OPTIONS  = list of options to pass to link command
CMAKE_REQUIRED_LIBRARIES = list of libraries to link
CMAKE_REQUIRED_QUIET = execute quietly without messages
CMAKE_EXTRA_INCLUDE_FILES = list of extra headers to include
