https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82130
Heiko Eißfeldt <heiko at hexco dot de> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |heiko at hexco dot de --- Comment #1 from Heiko Eißfeldt <heiko at hexco dot de> --- This variant works for me with: #define STRINGIFY(x) "x" #define _ASSERT_(expr) if (.not. (expr)) print *, STRINGIFY(expr) program test logical :: check = .false. _ASSERT_(check) end cpp -traditional-cpp -P -E issues/fortranStringify.f gives program test logical :: check = .false. if (.not. (check)) print *, "check" end This is with cpp 6.3.0 on ubuntu 17.04 amd64.