Re: [tegrarcm PATCH] Don't assume cryptopp is system-wide installed

[Allen Martin <amartin-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On Wed, Apr 20, 2016 at 11:27:35AM +0200, Thomas Petazzoni wrote:
> On Tue, 19 Apr 2016 16:57:45 -0700, Allen Martin wrote:
> 
> > What about the following as an alternative?
> > 
> > --
> > diff --git a/src/Makefile.am b/src/Makefile.am
> > index 3dad0e6d5e72..22410b3f81bf 100644
> > --- a/src/Makefile.am
> > +++ b/src/Makefile.am
> > @@ -1,5 +1,6 @@
> >  AM_CFLAGS = -Wall -std=c99
> > -AM_CPPFLAGS = -isystem /usr/include/$(CRYPTOLIB) $(LIBUSB_CFLAGS)
> > +CRYPTO_PREFIX = $(shell pkg-config --variable=includedir libcrypto++)
> 
> Using pkg-config is indeed a much better option. However, there are
> several gotchas:
> 
>  - First, calling pkg-config like this is not the correct way of using
>    pkg-config in autoconf/automake based packages. Instead, you should
>    use the PKG_CHECK_MODULES() autoconf macro, which will fill in for
>    you the <foo>_CFLAGS and <foo>_LIBS variables. Look at your
>    configure.ac, it is already used for the detection of libusb!

Unfortunately, libcrypto++ doesn't export any CFLAGS, so
PKG_CHECK_MODULES() doesn't work:

  arm@chrome~$ pkg-config --cflags libcrypto++
 
  arm@chrome~$ pkg-config --libs libcrypto++
  -lcrypto++  
  arm@chrome~$ pkg-config --print-variables libcrypto++
  exec_prefix
  prefix
  libdir
  includedir
  arm@chrome~$ pkg-config --variable=includedir libcrypto++
  /usr/include


> 
>  - Second, your logic assumes that libcrypto is called libcrypto++
>    while the crux of the matter is that on some platforms it is named
>    libcryptopp, on others it's called libcrypto++. Of course, this can
>    be solved in the configure.ac by calling PKG_CHECK_MODULES() for
>    both.

Looking at configure.ac I think there's another assumption baked in
too.  The compile test uses:

  LDFLAGS="$LDFLAGS -lcryptopp -lpthread"

> 
>  - Third, the upstream version of libcrypto++ does *not* install a
>    pkg-config file. The Debian packagers have added one, so you
>    probably have one on your Debian system, but if you build
>    libcrypto++ from source and simply "make install" it, you won't have
>    a .pc file that describes it for pkg-config.
> 
> The last point is the very reason why my patch didn't switch to simply
> use pkg-config.
> 

Well that sucks.  What about a command line option to configure to
specify the libcrypto++ include path?  My issue here is that if you
have the headers in a non standard location (like $HOME/include), the
compiler probably won't know how to find them either, and the compile
check will fail at configure time.

I'd like to change the -isystem to a plain -I too.  I think I added
that because the source code used #include "foo.h" instead of 
#include <foo.h> and I didn't want to make any source code changes
with the automake changes. 

-Allen