Fortran runtime warning: Extension: $ descriptor

Question

I am using a very old Fortran 77 code from third party (also very bugged). I have compiled with

FFLAGS=-O0 -Wall -g -fbacktrace -pedantic -Wextra

I am getting the warning in the title at runtime:

At line <number> of file <namefile>.f (unit=6, file='stdout')
Fortran runtime warning: Extension: $ descriptor

I would like to figure out what that means.

Answer 1

You should always show the code line number in the error or warning message, to which the line points.

The role of $ in

write(*,'(a$)') "string"

is to avoid going to the next line after printing "string" on the screen.

However, the descriptor is non-standard and therefore you are warned about this by the compiler.

The standard way is to use non-advancing input/output:

write(*,'(a)', advance="no") "string"