doc [skip ci]

Author: scivision

README.md

@@ -76,6 +76,10 @@ There are also some Fortran main programs calling C or C++.
 
 The examples "array", "malloc", "vector" show distinct ways to send arrays to/from Fortran with C and C++.
 
+### bool
+
+Made workaround for [nvfortran](https://forums.developer.nvidia.com/t/nvfortran-c-bool-bind-c-not-improper-value/291896).
+
 ### Error handling
 
 Using Fortran statement "stop" or "error stop" with a C/C++ main program works like with a Fortran main program.

src/bool/logbool.f90

@@ -20,6 +20,9 @@ logical(c_bool) function logical_not(L) bind(C)
 Ld = .false.
 
 !> workaround for nvfortran 24.3 etc.
+!! nvfortran reference guide:
+!! The logical constants .TRUE. and .FALSE. are defined to be the four-byte values -1 and 0 respectively.
+!! A logical expression is defined to be .TRUE. if its least significant bit is 1 and .FALSE. otherwise.
 ! logical_not = .not. L
 if(L) then
   logical_not = .false._C_BOOL