CMake check_function_exists only called one time in macro -

i have cmake macro calls check_function_exists() detect several math functions.

by output below, seems check_function_exists() called first time;

macro(nco_check_funcs func def) message(${argv0}) check_function_exists(${argv0} have_result) message(${have_result}) if (not have_result)   message("-- using nco defined version of ${argv0}")   add_definitions(-d${argv1}) endif() endmacro(nco_check_funcs)  nco_check_funcs(atan2 need_atan2) nco_check_funcs(acosf need_acosf) nco_check_funcs(asinf need_asinf) 

in example below macro called 3 times, output of check_function_exists() shows 1 time

atan2 -- looking atan2 -- looking atan2 - found 1 acosf 1 asinf 1 

those results of check_function_exists() cached.

check <function> provided libraries on system , store result in <variable>. <variable> created as internal cache variable.

add following begin of macro:

unset(have_result cache) 

or if want keep functionality of searching ones function (and cache result), need variable name depend on function this:

check_function_exists(${argv0} have_result_${argv0}) 

now each search function has own result variable.

reference

• unset()