Hello- I have a reproducible SEGV during GC of SMOBs on Guile 2.0.7. It was also present in 2.0.6. To reproduce compile main.c as $ gcc -std=gnu99 -shared -o smobbug.so -Wall -Wextra `pkg-config guile-2.0 --cflags --libs` -fPIC main.c Then with $ LD_PRELOAD=./smobbug.so LD_LIBRARY_PATH=. GUILE_LOAD_PATH=. guile ;; At the repl, load the lib (use-modules (smobbug)) ;; Make a SMOB to be GC'd (handlesmob-init) ;; Trigger a GC from the GC thread (string-length (make-string 10000000)) This gives Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0xb7d98b40 (LWP 20488)] 0xb7f251ab in smob_mark (addr=0x8608ff0, mark_stack_ptr=0xb7d90308, mark_stack_limit=0xb7d982f0, env=0) at smob.c:325 325 SCM_I_CURRENT_THREAD->current_mark_stack_ptr = mark_stack_ptr; Here's what's happening internally. When Guile starts up, it creates 3 threads * Initial thread * GC thread from scm_storage_prehistory GC_INIT() * signal delivery thread That second thread is the one from which automatic garbage collection occurs. The way that thread gets created, it has an scm_i_current_thread == NULL, apparently. So dereferencing scm_i_current_thread causes null dereference. And smob_mark() will dereference scm_i_current_thread when collecting a smob with a mark function. -Mike
smobbug.scm
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main.c
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