gcc: error: unrecognized command line option '-Wl'

[sagitter]

Hi again,

another issue that I do not know how to manage: gcc compiler does not recognize all -Wloptions.

-Wp, for example, is an option that I use often with gcc/g++ compilers, -Wl,-z,relro or -Wl,-z,now with the linker; why are they not permitted on Cantera?

Thanks.

[speth]

The problem is that the Cantera SConstruct file thinks that commas are delimiters between different options, e.g. if you write scons build cxx_flags=-g,-O2 it would understand to call gcc with the -g and -O2 options. But of course this doesn't work well with the use of commas for the exact same purpose within the -Wl option.

As a workaround, you can specify this option in cantera.conf as a list explicitly, i.e.

cxx_flags = ['-g', '-Wl,-z,relro', '-Wl,-z,now']

And of course the same applies for the other options for setting compiler/linker options.

[sagitter]

Thank you for reply.

Do options set in cantera.conf overwrite those ones set with scons command?

[speth]

It works the other way around: if you do not specify a value in the scons build command line, it will use one from cantera.conf. If you do specify a value to scons build, then that will be used to populate cantera.conf.

[speth]

Although there is a workaround, I think it might be preferable to modify the parsing of these compiler options (currently handled by the listify function in buildutils.py) so that flags like this can be passed in from the command line. Options for changing this are:

• Only allow spaces to be delimiters, which means that multiple values will need to be passed as quoted strings, e.g. scons build cxx_flags="-g -O2"
• Allow commas to be escaped in options like those above, e.g. scons build cxx_flags=-O2,-Wl\\,-z\\,relro.
  The second option has the advantage of not invalidating the currently-supported syntax, but double escaping required for the backslashes is kind of annoying.