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 additional flags to pass to the compiler. The string must be space-delimited--a ;-list will not work. The contents of
CMAKE_<LANG>_FLAGS
and its associated configuration-specific variable are automatically added to the compiler command before the contents ofCMAKE_REQUIRED_FLAGS
.
CMAKE_REQUIRED_DEFINITIONS
A ;-list of compiler definitions of the form
-DFOO
or-DFOO=bar
. A definition for the name specified by<resultVar>
will also be added automatically.
CMAKE_REQUIRED_INCLUDES
A ;-list of header search paths to pass to the compiler. These will be the only header search paths used--the contents of the
INCLUDE_DIRECTORIES
directory property will be ignored.
CMAKE_REQUIRED_LINK_OPTIONS
New in version 3.14.
A ;-list of options to add to the link command (see
try_compile()
for further details).
CMAKE_REQUIRED_LIBRARIES
A ;-list of libraries to add to the link command. These can be the name of system libraries or they can be Imported Targets (see
try_compile()
for further details).
CMAKE_REQUIRED_LINK_DIRECTORIES
New in version 3.31.
A ;-list of libraries search paths to pass to the linker (see
try_compile()
for further details).
CMAKE_REQUIRED_QUIET
New in version 3.1.
If this variable evaluates to a boolean true value, all status messages associated with the check will be suppressed.
CMAKE_EXTRA_INCLUDE_FILES
list of extra headers to include.