[petsc-dev] [petsc-users] Override PETSc compile options

[Satish Balay]

On Thu, 8 May 2014, Jed Brown wrote:

> Satish Balay <balay at mcs.anl.gov> writes:
> 
> > On Wed, 7 May 2014, TAY wee-beng wrote:
> >
> >> Hi Matt,
> >> 
> >> 
> >> Sorry, I mean during the compilation of my own codes using my own makefile.
> >> 
> > $ grep Wall arch-linux2-c-debug/conf/petscvariables 
> > FC_LINKER_FLAGS =    -fPIC -Wall -Wno-unused-variable -Wno-unused-dummy-argument -g -O0 
> > CC_FLAGS =  -fPIC -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -g3 -O0 
> > FC_FLAGS =  -fPIC -Wall -Wno-unused-variable -Wno-unused-dummy-argument -g -O0  
> > CXX_FLAGS =  -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -g -O0   -fPIC  
> > PCC_LINKER_FLAGS =    -fPIC -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -g3 -O0
> > PCC_FLAGS =  -fPIC -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -g3 -O0 
> > balay at asterix /home/balay/petsc (master)
> 
> Why does PETSc specify these redundantly using non-standard names as
> opposed to CFLAGS, CPPFLAGS, LDFLAGS, etc?  I never remember which name
> is used where so I have to grep conf/variables and petscvariables every
> time.  (I'd rather those be namespaced, but that's another issue.)

The above are internal names.

The user-interface provides a way to add flags [via CFLAGS,CPPFLAGS
etc..] the same way one can add flags to compilers - or mpicc [i.e not
replace the defaults]

[previously we did use CFLAGS,CPPFLAGS internally - and when users
[unintentionally] also used the same flags in their makefiles - the
defaults were replaced - causing unwanted behavior. Hence the current
usage.

Satish