_FORTIFY_SOURCE requirements

[dotnwat]

Seastar undefines _FORTIFY_SOURCE on all it's dependents. However, the comment here in CMakeLists.txt suggests it is only needed to be set on the compilation of thread.cc (indeed that seems to be the only file containing longjmp).

# We disable _FORTIFY_SOURCE because it generates false positives with longjmp() (src/core/thread.cc)

target_compile_options (seastar
  PUBLIC
    -U_FORTIFY_SOURCE)

We'd like to broaden the scope of _FORITFY_SOURCE by considering the removal of this public flag since it becomes viral in a Seastar application. We tried removing it, and things seemed ok, but we are wondering if we may be missing something important / would Seastar be opposed to removing this?

[avikivity]

3d75bab (2015)

If it no longer complains, we can remove it. Running the test suite in all modes should be sufficient.

[dotnwat]

Thanks. Additional discussion occurring in #2344.