Hi Matt, On Tue, Apr 20, 2021 at 06:46:27AM -0700, Matt Wette wrote: > > > On 4/20/21 5:47 AM, Matt Wette wrote: > > > > > > On 4/20/21 2:29 AM, Vladimir Zhbanov wrote: > > > Hi Guile users and devs, > > > > > > I'm the current maintainer of Lepton EDA suite, an about five year > > > old fork of geda-gaf with accent to moving more functionality to > > > Scheme code. I'm not sure if it is acceptable to advertise it > > > here, please let me know if not. I just know several Guix > > > packagers are reading this mailing list and would like to announce > > > a new version of Lepton, 1.9.14 has been released on April, 7: > > > > > > https://github.com/lepton-eda/lepton-eda/releases/tag/1.9.14-20210407 > > > > > > > > > > Sweet. Thanks for posting this. I will take a look at your problem. > > It'll require digging into the eda_..._dirs function. > > > > > > > The following should work as a complete program on a system w/ glib. > You need to first convert the result to a bytevector and then access the > elements (pointers) one at a time. Note that we don't know how big the > array returned from the C function is. I pick an oversized value of 100. > > (use-modules (system foreign)) > (use-modules (rnrs bytevectors)) > > (define glib (dynamic-link "libglib-2.0")) > > (define g-get-system-data-dirs > (let ((f (pointer->procedure > '* (dynamic-func "g_get_system_data_dirs" glib) (list))) > (bv-pointer-ref (cond > ((= (sizeof '*) 8) bytevector-u64-native-ref ) > ((= (sizeof '*) 4) bytevector-u32-native-ref ) > (else (error "hmmm")))) > (BIG 100)) > (lambda () > (let* ((r (f)) > (p (pointer->bytevector r (* BIG (sizeof '*))))) > (let loop ((ix 0)) > (let* ((ad (bv-pointer-ref p ix)) > (sp (make-pointer ad))) > (if (equal? %null-pointer sp) > '() > (cons (pointer->string sp) (loop (+ ix (sizeof '*))))))))))) > > (simple-format #t "~S" (g-get-system-data-dirs))
Thank you for your replies! Probably, I missed something here, so I'll try to elaborate a bit on my initial question. The function eda_get_system_data_dirs() mentioned in my first message has the same type, is defined the same way using dynamic-func though in liblepton instead of glib, and works on mostly the same array as glib's g_get_system_data_dirs(). The function I've shown works well and outputs the same results as yours. It simply uses a bit more upper level interface, IIUC. So the first question is: I wonder, if using bytevectors directly adds something here? Another issue is a little more confusing for me. I read in several places that even on the same system different compilators, say gcc and g++, may use different alignment even for basic C types like, say, double. What will they do on different platforms then? May it be that (alignof '*) will be twice greater than (sizeof '*)? In such a case using multiplied sizeof of pointer for searching the location of a pointer in memory would be just dangerous. I used sizeof in the first version of my code but started to doubt if it is correct and how portable it is. Thanks, Vladimir
