Re: Does Debian supports backticks in the Makefile?

[Greg Wooledge <greg@wooledge.org>]

On Mon, Jul 11, 2022 at 08:55:20AM -0500, Igor Korot wrote:
> This is what Gentoo generates:

> /bin/sh ../libtool  --tag=CXX   --mode=compile g++ -DHAVE_CONFIG_H -I.
> -I/home/igor/dbhandler/libpostgres -I..    -D__WXGTK__
> -I../../dbinterface `pg_config --includedir`  -g -O0 -MT
> libpostgres_la-database_postgres.lo -MD -MP -MF
> .deps/libpostgres_la-database_postgres.Tpo -c -o
> libpostgres_la-database_postgres.lo `test -f 'database_postgres.cpp'
> || echo '/home/igor/dbhandler/libpostgres/'`database_postgres.cpp

OK.  I see that you have the same "I forgot -I" bug in your Makefile.

> libtool: compile:  g++ -DHAVE_CONFIG_H -I.
> -I/home/igor/dbhandler/libpostgres -I.. -D__WXGTK__
> -I../../dbinterface /usr/include/postgresql-14 -g -O0 -MT
> libpostgres_la-database_postgres.lo -MD -MP -MF
> .deps/libpostgres_la-database_postgres.Tpo -c
> /home/igor/dbhandler/libpostgres/database_postgres.cpp  -fPIC -DPIC -o
> .libs/libpostgres_la-database_postgres.o

And there's the expanded command.  As you can see, it is wrong.

> g++: warning: /usr/include/postgresql-14: linker input file unused
> because linking not done

And you got a warning for the wrongness.

So, you are wondering why it actually compiled correctly.  Best guess:
on Gentoo, you have the libpq-fe.h file in a different directory, which
is in the C++ compiler's search list.  Maybe there's a symlink.  In any
case, the -I/usr/include/postgresql-14 argument isn't needed on Gentoo.

If you really want to dig into it, start with something like
"locate libpq-fe.h" and see all of the places it appears.  Then see what
directories are in the compiler's search list, etc.