Re: PTHREAD_CFLAGS provided by AX_PTHREAD where best to be attached?

[Bob Friesenhahn]

On Thu, 12 Jul 2018, Dudziak Krzysztof wrote:

> Hi,
> For makefiles which build piece of software in two separate steps: compilation 
> then linking,
> will it be better to attach  PTHREAD_CFLAGS to higher-level_CPPFLAGS than to 
> higher-level_CFLAGS variable?
> Autotools along with libtool are used here, user-level variables (CFLAGS, 
> CPPFLAGS) are not manipulated through whole build chain.
> I can manipulate variables only at Makefile.am -level.

CPPFLAGS is for the pre-processor while CFLAGS is applied (as well as 
CPPFLAGS) while compiling.  This means that putting the options in 
CFLAGS does work, although it would be better to deduce which options 
are for the pre-processor or the compiler and put them in the correct 
places.

> I learned gcc expects -pthread option which translates among others to some 
> preprocessor define,
> therefore I wonder if it won't be better to attach PTHREAD_CFLAGS to 
> higher-level_CPPFLAGS rather than
> to higher-level_CFLAGS.

It should not work to put -pthread in CPPFLAGS since it is a 
compiler-driver option and not a pre-processor (e.g. /usr/bin/cpp) 
option.

Only, -I, -D, and -U type options (see the manual page for 'cpp') 
should be put in CPPFLAGS.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/