/CMake 3.19


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

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 CheckCSourceCompiles). 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:


string of compile command line flags.


a ;-list of macros to define (-DFOO=bar).


a ;-list of header search paths to pass to the compiler.


a ;-list of options to add to the link command.


a ;-list of libraries to add to the link command. See policy CMP0075.


execute quietly without messages.

For example:


# 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)

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