CheckSymbolExists

Provides a macro to check if a symbol exists as a function, variable, or macro in C.

check_symbol_exists

check_symbol_exists(<symbol> <files> <variable>)

Check that the <symbol> is available after including given header <files> and store the result in a <variable>. Specify the list of files in one argument as a semicolon-separated list. <variable> will be created as an internal cache variable.

If the header files define the symbol as a macro it is considered available and assumed to work. If the header files declare the symbol as a function or variable then the symbol must also be available for linking (so intrinsics may not be detected). If the symbol is a type, enum value, or intrinsic it will not be recognized (consider using CheckTypeSize or CheckSourceCompiles). If the check needs to be done in C++, consider using CheckCXXSymbolExists instead.

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 of CMAKE_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

Added 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

Added in version 3.31.

A ;-list of libraries search paths to pass to the linker (see try_compile() for further details).

CMAKE_REQUIRED_QUIET

Added in version 3.1.

If this variable evaluates to a boolean true value, all status messages associated with the check will be suppressed.

For example:

include(CheckSymbolExists)

# Check for macro SEEK_SET
check_symbol_exists(SEEK_SET "stdio.h" HAVE_SEEK_SET)
# Check for function fopen
check_symbol_exists(fopen "stdio.h" HAVE_FOPEN)