Current CVS slime breaks when a large amount of text is printed to the REPL when using :fd-handler communication style on SBCL (tested on 1.0.19 and 1.0.20). For example: (loop for i below 1000 do (format t "~a ......................................................................~%" i)) stops partway through the loop, pressing enter makes it print a bit more, entering a form causes it to evaluate that form and print a bit more of the original output. backtrace from entering (break) while REPL was stopped in middle of output: Restarts: 0: [CONTINUE] Return from BREAK. 1: [RETRY] Retry SLIME REPL evaluation request. 2: [ABORT] Abort sending output to Emacs. 3: [RETRY] Retry SLIME REPL evaluation request. 4: [ABORT] Return to SLIME's top level. 5: [ABORT] Exit debugger, returning to top level. Backtrace: 0: (BREAK "break") 1: (SB-INT:SIMPLE-EVAL-IN-LEXENV (BREAK) #<NULL-LEXENV>) 2: (SWANK::EVAL-REGION "(break)\n") 3: ((LAMBDA ())) 4: (SWANK::TRACK-PACKAGE #<CLOSURE (LAMBDA #) {B1BED2D}>) 5: (SWANK::CALL-WITH-RETRY-RESTART "Retry SLIME REPL evaluation request." #<CLOSURE (LAMBDA #) {B1BEC15.. 6: (SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<CLOSURE (LAMBDA #) {B1BEBFD}>) 7: (SWANK::REPL-EVAL "(break)\n") 8: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SWANK:LISTENER-EVAL "(break)\n") #<NULL-LEXENV>) 9: (SWANK::EVAL-FOR-EMACS (SWANK:LISTENER-EVAL "(break)\n") "COMMON-LISP-USER" 74) 10: (SWANK::PROCESS-REQUESTS T NIL) 11: (SB-IMPL::SUB-SUB-SERVE-EVENT NIL NIL) 12: (SB-IMPL::SUB-SERVE-EVENT NIL NIL NIL) 13: (SB-SYS:WAIT-UNTIL-FD-USABLE 6 :INPUT NIL) 14: (SB-IMPL::REFILL-INPUT-BUFFER #<SB-SYS:FD-STREAM for "a socket" {AC5A119}>) 15: (SB-IMPL::INPUT-CHAR/UTF-8 #<SB-SYS:FD-STREAM for "a socket" {AC5A119}> NIL :EOF) 16: (PEEK-CHAR NIL #<SB-SYS:FD-STREAM for "a socket" {AC5A119}> NIL NIL #<unused argument>) 17: ((LAMBDA (SWANK-BACKEND::STREAMS &OPTIONAL SWANK-BACKEND::TIMEOUT)) (#<SB-SYS:FD-STREAM for "a socke.. 18: (SWANK::WAIT-FOR-EVENT/EVENT-LOOP (:EMACS-PONG 13) NIL) 19: (SWANK::WAIT-FOR-EVENT (:EMACS-PONG 13) NIL) 20: (SWANK::SEND-USER-OUTPUT ..) 21: ((LAMBDA ())) 22: ((LAMBDA ())) 23: ((FLET #:WITHOUT-INTERRUPTS-BODY-[CALL-WITH-RECURSIVE-LOCK]508)) 24: (SB-THREAD::CALL-WITH-RECURSIVE-LOCK ..) 25: ((LAMBDA (SWANK-BACKEND::LOCK FUNCTION)) #S(SB-THREAD:MUTEX :NAME "buffer write lock" :%OWNER #<SB-T.. 26: ((SB-PCL::FAST-METHOD STREAM-FINISH-OUTPUT (SWANK-BACKEND::SLIME-OUTPUT-STREAM)) #(3 NIL 2 NIL 5 NIL.. 27: ((LAMBDA ())) 28: ((FLET #:WITHOUT-INTERRUPTS-BODY-[CALL-WITH-RECURSIVE-LOCK]508)) 29: (SB-THREAD::CALL-WITH-RECURSIVE-LOCK ..) 30: ((LAMBDA (SWANK-BACKEND::LOCK FUNCTION)) #S(SB-THREAD:MUTEX :NAME "buffer write lock" :%OWNER #<SB-T.. 31: ((SB-PCL::FAST-METHOD STREAM-WRITE-STRING (SWANK-BACKEND::SLIME-OUTPUT-STREAM T)) ..) 32: (WRITE-STRING " ......................................................................" #<SWANK-BACK.. 33: (SB-FORMAT::INTERPRET-DIRECTIVE-LIST #<SWANK-BACKEND::SLIME-OUTPUT-STREAM {A6EC099}> (" .............. 34: (SB-FORMAT::%FORMAT #<SWANK-BACKEND::SLIME-OUTPUT-STREAM {A6EC099}> "~a .............................. 35: (FORMAT T "~a ......................................................................~%")[:EXTERNAL] 36: ((LAMBDA ())) 37: (SB-INT:SIMPLE-EVAL-IN-LEXENV (LOOP FOR I BELOW 1000 DO ...) #<NULL-LEXENV>) 38: (SWANK::EVAL-REGION "(loop for i below 1000 do (format t \"~a ........................................ 39: ((LAMBDA ())) 40: (SWANK::TRACK-PACKAGE #<CLOSURE (LAMBDA #) {AFDEC95}>) 41: (SWANK::CALL-WITH-RETRY-RESTART "Retry SLIME REPL evaluation request." #<CLOSURE (LAMBDA #) {AFDEB7D.. 42: (SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<CLOSURE (LAMBDA #) {AFDEB65}>) 43: (SWANK::REPL-EVAL "(loop for i below 1000 do (format t \"~a .......................................... 44: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SWANK:LISTENER-EVAL "(loop for i below 1000 do (format t \"~a ......... 45: (SWANK::EVAL-FOR-EMACS (SWANK:LISTENER-EVAL "(loop for i below 1000 do (format t \"~a ................ 46: (SWANK::PROCESS-REQUESTS T NIL) 47: ((LAMBDA ())) 48: ((LAMBDA (SWANK-BACKEND::HOOK SWANK-BACKEND::FUN)) #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (.. 49: (SWANK::CALL-WITH-REDIRECTED-IO #<SWANK::CONNECTION {AC5AD59}> #<CLOSURE (LAMBDA #) {AFCBF35}>) 50: (SWANK::CALL-WITH-CONNECTION #<SWANK::CONNECTION {AC5AD59}> #<CLOSURE (LAMBDA #) {AFCBF25}>) 51: (SWANK::HANDLE-REQUESTS #<SWANK::CONNECTION {AC5AD59}> T NIL) 52: (SB-IMPL::SUB-SUB-SERVE-EVENT NIL NIL) 53: (SB-IMPL::SUB-SERVE-EVENT NIL NIL NIL) 54: (SB-SYS:WAIT-UNTIL-FD-USABLE 0 :INPUT NIL) 55: (SB-IMPL::REFILL-INPUT-BUFFER #<SB-SYS:FD-STREAM for "standard input" {A6E57F1}>) 56: (SB-IMPL::INPUT-CHAR/UTF-8 #<SB-SYS:FD-STREAM for "standard input" {A6E57F1}> NIL #:EOF-OBJECT) 57: (READ-CHAR #<SB-SYS:FD-STREAM for "standard input" {A6E57F1}> NIL #:EOF-OBJECT #<unused argument>) 58: (READ-CHAR #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {90DA579}> NIL #:EOF-OBJECT #<unused argument>) 59: (READ-PRESERVING-WHITESPACE #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {90DA579}> NIL (NIL) T) 60: (READ-PRESERVING-WHITESPACE #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {90DA579}> NIL (NIL) NIL) 61: (READ #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {90DA579}> NIL (NIL) NIL) 62: (SB-IMPL::REPL-READ-FORM-FUN #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {90DA579}> #<unavailable argume.. 63: (SB-IMPL::REPL-FUN NIL) 64: (SB-IMPL::REPL-FUN NIL)[:EXTERNAL] 65: ((LAMBDA ())) 66: ((LAMBDA ()))[:EXTERNAL] 67: (SB-IMPL::%WITH-REBOUND-IO-SYNTAX #<CLOSURE (LAMBDA #) {A6E8AD5}>) 68: (SB-IMPL::TOPLEVEL-REPL NIL) 69: (SB-IMPL::TOPLEVEL-INIT) 70: ((LABELS SB-IMPL::RESTART-LISP))