Changed run location of INIT segment.

So far the INIT segment was run from the later heap+stack. Now the INIT segment is run from the later BSS. The background is that so far the INIT segment was pretty small (from $80 to $180 bytes). But upcoming changes will increase the INIT segment in certain scenarios up to ~ $1000 bytes. So programs with very limited heap+stack might just not been able to move the INIT segment to its run location. But moving the INIT segment to the later BSS allows it to occupy the later BSS+heap+stack.

In order to allow that the constructors are _NOT_ allowed anymore to access the BSS. Rather they must use the DATA segment or the new INITBSS segment. The latter isn't cleared at any point so the constructors may use it to expose values to the main program. However they must make sure to always write the values as they are not pre-initialized.

libsrc/vic20/crt0.s

@@ -86,7 +86,7 @@ L2:     lda     zpsave,x
 
 ; ------------------------------------------------------------------------
 
-.segment        "ZPSAVE"
+.segment        "INITBSS"
 
 zpsave: .res    zpspace
 

libsrc/vic20/mainargs.s

@@ -28,10 +28,9 @@
         .include        "vic20.inc"
 
 
-
 MAXARGS  = 10                   ; Maximum number of arguments allowed
 REM      = $8f                  ; BASIC token-code
-NAME_LEN = 16                   ; maximum length of command-name
+NAME_LEN = 16                   ; Maximum length of command-name
 
 ; Get possible command-line arguments. Goes into the special INIT segment,
 ; which may be reused after the startup code is run
@@ -42,24 +41,24 @@ initmainargs:
 
 ; Assume that the program was loaded, a moment ago, by the traditional LOAD
 ; statement.  Save the "most-recent filename" as argument #0.
-; Because the buffer, that we're copying into, was zeroed out,
-; we don't need to add a NUL character.
-;
+
+        lda     #0              ; The terminating NUL character
         ldy     FNAM_LEN
         cpy     #NAME_LEN + 1
         bcc     L1
-        ldy     #NAME_LEN - 1   ; limit the length
+        ldy     #NAME_LEN       ; Limit the length
+        bne     L1              ; Branch always
 L0:     lda     (FNAM),y
-        sta     name,y
-L1:     dey
+L1:     sta     name,y
+        dey
         bpl     L0
         inc     __argc          ; argc always is equal to, at least, 1
 
 ; Find the "rem" token.
-;
+
         ldx     #0
 L2:     lda     BASIC_BUF,x
-        beq     done            ; no "rem," no args.
+        beq     done            ; No "rem," no args.
         inx
         cmp     #REM
         bne     L2
@@ -71,7 +70,7 @@ next:   lda     BASIC_BUF,x
         beq     done            ; End of line reached
         inx
         cmp     #' '            ; Skip leading spaces
-        beq     next            ;
+        beq     next
 
 ; Found start of next argument. We've incremented the pointer in X already, so
 ; it points to the second character of the argument. This is useful since we
@@ -126,15 +125,13 @@ done:   lda     #<argv
         stx     __argv + 1
         rts
 
-; These arrays are zeroed before initmainargs is called.
-; char  name[16+1];
-; char* argv[MAXARGS+1]={name};
-;
-.bss
+.segment        "INITBSS"
+
 term:   .res    1
 name:   .res    NAME_LEN + 1
 
 .data
+
+; char* argv[MAXARGS+1]={name};
 argv:   .addr   name
         .res    MAXARGS * 2
-