Flang accepts -module-dir as short-style option

[Meinersbur]

f820625 claims that gfortran would treat -module-dir exactly like -J. This is not thee case:

$ gfortran -J/home/meinersbur/finclude 
gfortran: fatal error: no input files
$ gfortran -module-dir/home/meinersbur/finclude
gfortran: error: unrecognized command-line option ‘-module-dir/home/meinersbur/finclude’

But flang accepts both:

$ flang -J/home/meinersbur/finclude
flang-22: error: no input files     
$ gfortran -module-dir/home/meinersbur/finclude          
flang-22: error: no input files         

Flang is confusing short- and long-format command line arguments. The way to pass argument to long-style option is one of:

$ flang -module-dir=/home/meinersbur/finclude          
flang-22: error: no input files         
$ flang -module-dir /home/meinersbur/finclude          
flang-22: error: no input files    

The consequence is that if flang would introduce a new option such as -module-directives, it could not be distiguished from -module-dir=ectives.

[llvmbot]

@llvm/issue-subscribers-flang-driver

Author: Michael Kruse (Meinersbur)

f820625 claims that gfortran would treat `-module-dir` exactly like `-J`. This is not thee case:

$ gfortran -J/home/meinersbur/finclude 
gfortran: fatal error: no input files
$ gfortran -module-dir/home/meinersbur/finclude
gfortran: error: unrecognized command-line option ‘-module-dir/home/meinersbur/finclude’

But flang accepts both:

$ flang -J/home/meinersbur/finclude
flang-22: error: no input files     
$ gfortran -module-dir/home/meinersbur/finclude          
flang-22: error: no input files         

Flang is confusing short- and long-format command line arguments. The way to pass argument to long-style option is one of:

$ flang -module-dir=/home/meinersbur/finclude          
flang-22: error: no input files         
$ flang -module-dir /home/meinersbur/finclude          
flang-22: error: no input files    

The consequence is that if flang would introduce a new option such as -module-directives, it could not be distiguished from -module-dir=ectives.

[tarunprabhu]

Strange. On gfortran, -J seems to work, but -module-dir does not

$ gfortran hello.f90 -o hello.o -Jmods

$ gfortran hello.f90 -o hello.o -module-dir=mods 
gfortran: error: unrecognized command-line option ‘-module-dir=mods’

$ gfortran hello.f90 -o hello.o -module-dir mods
gfortran: error: unrecognized command-line option ‘-module-dir’; did you mean ‘--module-file=’? 

In any case, I agree that long-form options should be separated, not joined.

Out of curiosity, do you have a need for an option such as -module-directives

[Meinersbur]

The gcc/gfortran command line format distinguishes between short form options (such as -I, -o, -L, ...) and long form options (-march, -fplugin, -fsyntax-only, -print-file-name). Only short form options can take arguments joined such as -lthreads. As a result, there cannot be a another option that starts with -l such as -liberty¹.

There is currently is no need for an option such as -module-directives, but imagine flang would introduce a more obvious short-form switch such as -s, which would block us into the future of introducing any new command line flag start with -s (it would already conflct with with -save-temps). We should not introduce new short-format flags, but it mostly annoys me because we could not properly categorize long- and short-format options.

I should mention that CMake already makes use of the broken -module-dir<dir> (e.g. -module-dirflang-rt/lib/runtime is added during the Flang-RT build process) when dectecting LLVMFlang, so I fear we are stuck with it now, and hope that gfortran does not introduce a new -module-directives flag.

Footnotes

1. https://en.wikipedia.org/wiki/Libiberty ↩