[petsc-users] How do I supply the compiler PIC flag via CFLAGS, CXXXFLAGS, and FCFLAGS

[Smith, Barry F.]

  Works for Intel and PGI compiles (the version I checked)

bsmith at es:~$ pgcc check-pic.c  -PIC
pgcc-Error-Unknown switch: -PIC
bsmith at es:~$ pgcc check-pic.c  -fPIC
bsmith at es:~$ pgcc check-pic.c 
PGC-F-0249-#error --  "no-PIC" (check-pic.c: 2)
PGC/x86-64 Linux 19.3-0: compilation aborted
bsmith at es:~$ icc check-pic.c 
check-pic.c(2): error: #error directive: "no-PIC"
  #error "no-PIC"
   ^

compilation aborted for check-pic.c (code 2)
bsmith at es:~$ icc check-pic.c -PIC
icc: command line warning #10006: ignoring unknown option '-PIC'
check-pic.c(2): error: #error directive: "no-PIC"
  #error "no-PIC"
   ^

compilation aborted for check-pic.c (code 2)
bsmith at es:~$ icc check-pic.c -fPIC
bsmith at es:~$ 


You are the man!


> On May 28, 2019, at 12:29 PM, Lisandro Dalcin via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> 
> 
> On Tue, 28 May 2019 at 18:19, Jed Brown <jed at jedbrown.org> wrote:
> Lisandro Dalcin via petsc-users <petsc-users at mcs.anl.gov> writes:
> 
> > On Tue, 28 May 2019 at 17:31, Balay, Satish via petsc-users <
> > petsc-users at mcs.anl.gov> wrote:
> >
> >> Configure.log shows '--with-pic=1' - hence this error.
> >>
> >> Remove '--with-pic=1' and retry.
> >>
> >>
> > Nonsense. Why this behavior? Building a static library with PIC code is a
> > perfectly valid use case.
> 
> And that's what will happen because Inge passed -fPIC in CFLAGS et al.
> 
> Do you know how we could confirm that PIC code is generated without
> attempting to use shared libraries?
> 
> 
> I know how to do it with the `readelf` command for ELF objects. I even know how to do it compile-time for GCC and clang. Maybe Intel also works this way. I do not know about a general solution, though.
> 
> $ cat check-pic.c 
> #ifndef __PIC__
> #error "no-PIC"
> #endif
> 
> $ gcc -c check-pic.c -fPIC
> 
> $ clang -c check-pic.c -fPIC
> 
> $ gcc -c check-pic.c
> check-pic.c:2:2: error: #error "no-PIC"
>     2 | #error "no-PIC"
>       |  ^~~~~
> 
> $ clang -c check-pic.c
> check-pic.c:2:2: error: "no-PIC"
> #error "no-PIC"
>  ^
> 1 error generated.
>  
> -- 
> Lisandro Dalcin
> ============
> Research Scientist
> Extreme Computing Research Center (ECRC)
> King Abdullah University of Science and Technology (KAUST)
> http://ecrc.kaust.edu.sa/