invoke-via-macro.F90

#include "assert_macros.h"

program invoke_via_macro
  !! Demonstrate how to invoke the 'assert' subroutine using a preprocessor macro that facilitates
  !! the complete removal of the call in the absence of the compiler flag: -DASSERTIONS
  use assert_m ! <--- this is the recommended use statement
    !! If an "only" clause is employed above, the symbols required by the
    !! macro expansion are subject to change without notice between versions.
    !! You have been warned!
  implicit none

#if !ASSERTIONS
  print *
  print *,'To enable the "call_assert" invocations, define the ASSERTIONS macro. e.g.:'
  print *,' fpm run --example invoke-via-macro --flag "-DASSERTIONS -fcoarray=single -ffree-line-length-0"'
  print *
#endif

  ! The C preprocessor will convert each call_assert* macro below into calls that enforce the assertion
  ! whenever the ASSERTIONS macro is defined to non-zero (e.g. via the -DASSERTIONS compiler flag).
  ! Whenever the ASSERTIONS macro is undefined or defined to zero (e.g. via the -DASSERTIONS=0 compiler flag),
  ! these calls will be entirely removed by the preprocessor.

  call_assert(1==1) ! true assertion
  call_assert_describe(2>0,    "example assertion invocation via macro") ! true assertion
#if ASSERTIONS
    print *
    print *,'Here comes the expected assertion failure:'
    print *
#endif
 !call_assert(1+1>2) ! example false assertion without description
  call_assert_describe(1+1>2, "Mathematics is broken!") ! false assertion with description

end program invoke_via_macro