gprof not producing annotated source

[Chris Stankevitz]

Hello,

Facts:

a) 'gprof ./a.out' produces lots of profiling info

b) 'gprof --annotated-source ./a.out' produces no output

c) 'gprof --line --annotated-source ./a.out' produces no output but uses more CPU than b)

d) I'm compiling and linking with this command: g++ -Wall -O0 -march=native -fprofile-arcs -ftest-coverage *.cpp -lusrp -lpthread -lfftw3 -lfftw3f -pg


Questions:

1) Why does b) produce no output?

2) Why does c) use more CPU than b) when --line is documented as "This feature works with programs compiled by older versions of the "gcc" compiler."

Thank you!

Chris