fix for data left on return stack when AA tree is empty

startup.4th

@@ -2289,10 +2289,9 @@ SYSTEM DEFINITIONS
 \ From this point on we only execute threaded FORTH words defined in this file
 \ *****************************************************************************
 
-ONLY FORTH
-ALSO UTILITY
-ALSO SYSTEM
-ALSO
+ONLY FORTH ALSO
+UTILITY ALSO
+SYSTEM ALSO
 
 SYSTEM DEFINITIONS
 
@@ -2753,19 +2752,23 @@ UTILITY DEFINITIONS
    AA>ROOT @ AA-TRAVERSE-NODE ;
 
 : AA-ITERATE  ( i*x xt aa-tree -- j*x )
-   NULL >R AA>ROOT @
-   BEGIN ?DUP WHILE
+   AA>ROOT @ ?DUP IF
+      NULL >R
+      BEGIN
          DUP >R AA>LEFT @
          BEGIN ?DUP 0= WHILE
             R> ?DUP 0= IF DROP EXIT THEN
             2DUP 2>R SWAP EXECUTE 2R>
             AA>RIGHT @
          REPEAT
-   REPEAT ▪ DROP ;
+      AGAIN
+   THEN ▪ DROP ;
 
 : AA-#NODES  ( aa-tree -- u )
    >R 0 { DROP 1+ } R> AA-ITERATE ;
 
+LINUX ALSO
+
 LINUX DEFINITIONS
 
 STRUCT
@@ -2808,11 +2811,9 @@ ENDSTRUCT FILE%
 
 { CONTAINEROF FILE>NODE ▪ FILE>FD @ } ' <=> NEW-AA-TREE CONSTANT FILES
 
-ALSO LINUX
 open_how% %VARIABLE OPEN-HOW
 stat64% %VARIABLE STAT64-RESULT
 signed-long-long% %VARIABLE LLSEEK-RESULT
-PREVIOUS
 
 : FD>FILE  ( fileid -- file-addr )
    FILES AA-LOOKUP ?DUP 0= "unknown file ID" ?FAIL ;
@@ -2828,8 +2829,6 @@ UTILITY DEFINITIONS
 
 FORTH DEFINITIONS
 
-ALSO LINUX
-
 O_RDONLY CONSTANT R/O  ( -- fam )
 O_WRONLY CONSTANT W/O  ( -- fam )
 O_RDWR   CONSTANT R/W  ( -- fam )
@@ -2881,8 +2880,55 @@ O_RDWR   CONSTANT R/W  ( -- fam )
    0<> IF EXCP-FILE-IO THROW THEN
    STAT64-RESULT stat64>size 2@ SWAP ;
 
-: READ-FILE  ( c-addr u1 fileid -- u2 ) ;
-: READ-LINE  ( c-addr u1 fileid -- u2 t=eof ) ;
+UTILITY DEFINITIONS
+
+: (READ-CHAR)  ( file-addr -- c TRUE | FALSE )
+   >R
+   R@ FILE>LEFTOVER 2@ NIP 0= IF
+      R@ FILE>FD @ R@ FILE>BUFFER @ FILE-BUFFER-BYTES
+         SYS_READ SYSCALL3-RETRY
+      DUP 0< IF DROP EXCP-FILE-IO THROW THEN
+      DUP FILE-BUFFER-BYTES U> "read more data than requested" ?FAIL
+      R@ FILE>BUFFER @ SWAP R@ FILE>LEFTOVER 2!
+   THEN
+   R@ FILE>LEFTOVER 2@ DUP IF
+      OVER C@ -ROT 1/STRING R@ FILE>LEFTOVER 2!
+      R@ FILE>POSITION DUP 2@ 1# D+ ROT 2!
+      TRUE
+   ELSE
+      2DROP FALSE
+   THEN
+   RDROP ;
+
+FORTH DEFINITIONS
+
+: READ-FILE  ( c-addr u1 fileid -- u2 )
+   FD>FILE LOCALS| addr max file |
+      0 BEGIN
+         DUP max U<
+      WHILE
+         file (READ-CHAR)
+      WHILE
+         OVER addr + C!
+         1+
+      REPEAT
+   ENDLOCALS ;
+
+: READ-LINE  ( c-addr u1 fileid -- u2 t=eof )
+   FD>FILE LOCALS| addr max file |
+      FALSE 0 BEGIN
+         DUP max U<
+      WHILE
+         file (READ-CHAR)
+         DUP 0= IF NIP TRUE SWAP THEN
+      WHILE
+         DUP LF <> DUP 0= IF NIP THEN
+      WHILE
+         OVER addr + C!
+         1+
+      REPEAT
+      SWAP
+   ENDLOCALS ;
 
 : WRITE-FILE  ( c-addr u fileid -- )
    FD>FILE >R