It depends on your makefile - and how you are over-riding the targets. 1. Why add -rpath to CXXFLAGS, and not LDFLAGS? The following work for me with the default makefile format used by petsc examples balay@ pj01: ~/test$ ls ex2. cpp makefile
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It depends on your makefile - and how you are over-riding the targets.

1. Why add -rpath to CXXFLAGS, and not LDFLAGS?

The following work for me with the default makefile format used by petsc examples

balay@pj01:~/test$ ls
ex2.cpp  makefile
balay@pj01:~/test$ cat makefile 

include ${PETSC_DIR}/lib/petsc/conf/variables
include ${PETSC_DIR}/lib/petsc/conf/rules

balay@pj01:~/test$ make ex2
mpicxx -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -Wno-lto-type-mismatch -Wno-psabi -fstack-protector -fvisibility=hidden -g -O0  -I/home/balay/petsc/include -I/home/balay/petsc/arch-linux-c-debug/include     ex2.cpp  -Wl,-rpath,/home/balay/petsc/arch-linux-c-debug/lib -L/home/balay/petsc/arch-linux-c-debug/lib -Wl,-rpath,/software/mpich-4.1.1/lib -L/software/mpich-4.1.1/lib -Wl,-rpath,/usr/lib/gcc/x86_64-redhat-linux/13 -L/usr/lib/gcc/x86_64-redhat-linux/13 -lpetsc -llapack -lblas -ltriangle -lm -lX11 -lmpifort -lmpi -lgfortran -lm -lgfortran -lm -lgcc_s -lquadmath -lstdc++ -lquadmath -o ex2
balay@pj01:~/test$ make clean
balay@pj01:~/test$ make ex2 LDFLAGS=-foobar
mpicxx -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -Wno-lto-type-mismatch -Wno-psabi -fstack-protector -fvisibility=hidden -g -O0  -I/home/balay/petsc/include -I/home/balay/petsc/arch-linux-c-debug/include    -foobar ex2.cpp  -Wl,-rpath,/home/balay/petsc/arch-linux-c-debug/lib -L/home/balay/petsc/arch-linux-c-debug/lib -Wl,-rpath,/software/mpich-4.1.1/lib -L/software/mpich-4.1.1/lib -Wl,-rpath,/usr/lib/gcc/x86_64-redhat-linux/13 -L/usr/lib/gcc/x86_64-redhat-linux/13 -lpetsc -llapack -lblas -ltriangle -lm -lX11 -lmpifort -lmpi -lgfortran -lm -lgfortran -lm -lgcc_s -lquadmath -lstdc++ -lquadmath -o ex2
g++: error: unrecognized command-line option ‘-foobar’
make: *** [<builtin>: ex2] Error 1
balay@pj01:~/test$ make ex2 CXXFLAGS=-foobar
mpicxx -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -Wno-lto-type-mismatch -Wno-psabi -fstack-protector -fvisibility=hidden -g -O0 -foobar -I/home/balay/petsc/include -I/home/balay/petsc/arch-linux-c-debug/include     ex2.cpp  -Wl,-rpath,/home/balay/petsc/arch-linux-c-debug/lib -L/home/balay/petsc/arch-linux-c-debug/lib -Wl,-rpath,/software/mpich-4.1.1/lib -L/software/mpich-4.1.1/lib -Wl,-rpath,/usr/lib/gcc/x86_64-redhat-linux/13 -L/usr/lib/gcc/x86_64-redhat-linux/13 -lpetsc -llapack -lblas -ltriangle -lm -lX11 -lmpifort -lmpi -lgfortran -lm -lgfortran -lm -lgcc_s -lquadmath -lstdc++ -lquadmath -o ex2
g++: error: unrecognized command-line option ‘-foobar’
make: *** [<builtin>: ex2] Error 1
balay@pj01:~/test$ 

Satish

On Tue, 9 Jul 2024, Qiyue Lu wrote:

> Hello,
> I am trying to compile a *.cpp code under PETSc environment. An additional
> flag is needed to link the metis partition library.
> ##############
> # This line is necessary for linking, remember need this flag in both
> compiler options and linking options
> LDFLAGS= -fopenmp -lpmix -lmetis
> 
> # This line is required for using some 'helper' function like
> cudaErrorCheck from samples suite
> CXXFLAGS +=
> -Wl,-rpath,/sw/spack/deltas11-2023-03/apps/linux-rhel8-zen/gcc-8.5.0/metis-5.1.0-v5iddu2/lib
> # This two lines are required for using PETSc
> include ${PETSC_DIR}/lib/petsc/conf/variables
> include ${PETSC_DIR}/lib/petsc/conf/rules
> ##############
> 
> However, adding "CXXFLAGS += -Wl,-rpath, path_to_lib" in the makefile under
> the same directory, is not working. And CPPFLAGS and CXXPPFLAGS won't work
> either. No errors while compiling, but cannot find the metis.o while
> running the binary. Another confusing point is, in the compilation flash
> screen, LDFLAGS options can be found, but CXXFLAGS cannot.
> 
> Could you please inform me how to add additional flags in the makefile?
> 
> Thanks,
> Qiyue Lu
> 

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