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. Results are reported in the following variables:
HAVE_<variable>
Holds a true or false value indicating whether the type exists.
<variable>
Holds one of the following values:
<size>
Type has non-zero size
<size>
.0
Type has architecture-dependent size. This may occur when
CMAKE_OSX_ARCHITECTURES
has multiple architectures. In this case<variable>_CODE
contains 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>
.- "" (empty string)
Type does not exist.
<variable>_CODE
Holds C preprocessor code to define the macro
<variable>
to the size of the type, or to leave the macro undefined if the type does not exist.
The options are:
BUILTIN_TYPES_ONLY
Support only compiler-builtin types. If 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.LANGUAGE <language>
Use the
<language>
compiler to perform the check. Acceptable values areC
andCXX
.
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
New in version 3.14: list of options to pass to link command.
CMAKE_REQUIRED_LIBRARIES
list of libraries to link.
CMAKE_REQUIRED_QUIET
New in version 3.1: execute quietly without messages.
CMAKE_EXTRA_INCLUDE_FILES
list of extra headers to include.