Jean Abou Samra <j...@abou-samra.fr> writes: > Le 17/06/2022 à 23:49, David Kastrup a écrit : >> Jean Abou Samra <j...@abou-samra.fr> writes: >> >>> By the way, I have a side question. Suppose I have determined >>> that I need to mark the local variable scm_obj with >>> scm_remember_upto_here in this code: >>> >>> SCM scm_obj = get_it_from_somewhere (); >>> >>> return something_that_needs_scm_obj_alive; >>> >>> // Is this correct? >>> scm_remember_upto_here (scm_obj); >>> >>> >>> Might the compiler detect that return exits the function and >>> ignore the scm_remember_upto_here? >> return; releases the stack frame. "return >> something_that_needs_scm_obj_alive;" is not a valid pattern unless the >> returned value itself is an SCM that will cover scm_obj in its GC scope. > > > > Well, I was thinking of something like this: > > Pitch *p = unsmob<Pitch> (scm_pitch); > return *p; > scm_remember_upto_here (scm_pitch); // ??
Not a good pattern. Just use Pitch p = ... scm_remember_upto_here is not a magic instruction to the compiler but just C code that requires scm_pitch to be still defined. Putting it into a code path that is not being executed is useless. -- David Kastrup
