tweak program start initialization and fix cleanup at exit for atari and pet compiler targets

codeGenCpu6502/src/prog8/codegen/cpu6502/ProgramAndVarsGen.kt

@@ -103,6 +103,9 @@ internal class ProgramAndVarsGen(
                         asmgen.out("  .null  $9e, format(' %d ', prog8_entrypoint), $3a, $8f, ' prog8'")
                         asmgen.out("+\t.word  0")
                         asmgen.out("prog8_entrypoint\t; assembly code starts here")
+                        asmgen.out("  cld")
+                        asmgen.out("  tsx  ; save stackpointer for sys.exit()")
+                        asmgen.out("  stx  prog8_lib.orig_stackpointer")
                         if(!options.noSysInit)
                             asmgen.out("  jsr  sys.init_system")
                         asmgen.out("  jsr  sys.init_system_phase2")
@@ -110,6 +113,9 @@ internal class ProgramAndVarsGen(
                     CbmPrgLauncherType.NONE -> {
                         asmgen.out("; ---- program without basic sys call ----")
                         asmgen.out("* = ${options.loadAddress.toHex()}")
+                        asmgen.out("  cld")
+                        asmgen.out("  tsx  ; save stackpointer for sys.exit()")
+                        asmgen.out("  stx  prog8_lib.orig_stackpointer")
                         if(!options.noSysInit)
                             asmgen.out("  jsr  sys.init_system")
                         asmgen.out("  jsr  sys.init_system_phase2")
@@ -119,6 +125,9 @@ internal class ProgramAndVarsGen(
             OutputType.XEX -> {
                 asmgen.out("; ---- atari xex program ----")
                 asmgen.out("* = ${options.loadAddress.toHex()}")
+                asmgen.out("  cld")
+                asmgen.out("  tsx  ; save stackpointer for sys.exit()")
+                asmgen.out("  stx  prog8_lib.orig_stackpointer")
                 if(!options.noSysInit)
                     asmgen.out("  jsr  sys.init_system")
                 asmgen.out("  jsr  sys.init_system_phase2")
@@ -149,7 +158,10 @@ internal class ProgramAndVarsGen(
                 asmgen.out("  jsr  p8b_main.p8s_start |  lda  #0 |  sta ${"$"}ff00")
                 asmgen.out("  jmp  sys.cleanup_at_exit")
             }
-            else -> asmgen.jmp("p8b_main.p8s_start")
+            else -> {
+                asmgen.out("  jsr  p8b_main.p8s_start")
+                asmgen.out("  jmp  sys.cleanup_at_exit")
+            }
         }
     }
 
@@ -451,22 +463,7 @@ internal class ProgramAndVarsGen(
     }
 
     private fun entrypointInitialization() {
-        asmgen.out("; program startup initialization")
+        // initialize block-level (global) variables at program start
-        asmgen.out("  cld |  tsx |  stx  prog8_lib.orig_stackpointer    ; required for sys.exit()")
-        // set full BSS area to zero
-        asmgen.out("""
-    .if  prog8_bss_section_size>0
-    ; reset all variables in BSS section to zero
-	lda  #<prog8_bss_section_start
-	ldy  #>prog8_bss_section_start
-	sta  P8ZP_SCRATCH_W1
-	sty  P8ZP_SCRATCH_W1+1
-	ldx  #<prog8_bss_section_size
-	ldy  #>prog8_bss_section_size
-	lda  #0
-	jsr  prog8_lib.memset
-    .endif""")
-
         blockVariableInitializers.forEach {
             if (it.value.isNotEmpty())
                 asmgen.out("  jsr  ${it.key.name}.prog8_init_vars")
@@ -517,9 +514,8 @@ internal class ProgramAndVarsGen(
             arrayVariable2asm(varname, it.alloc.dt, it.value, null)
         }
 
-        asmgen.out("""+        
+        // zero out the BSS area
-                    clv
+        asmgen.out("+    jsr  prog8_lib.program_startup_clear_bss")
-                    clc""")
     }
 
     private class ZpStringWithInitial(

compiler/res/prog8lib/atari/syslib.p8

@@ -44,6 +44,22 @@ sys {
         }}
     }
 
+    asmsub  cleanup_at_exit() {
+        ; executed when the main subroutine does rts
+        %asm {{
+_exitcodeCarry = *+1
+            lda  #0
+            lsr  a
+_exitcode = *+1
+            lda  #0        ; exit code possibly modified in exit()
+_exitcodeX = *+1
+            ldx  #0
+_exitcodeY = *+1
+            ldy  #0
+            rts
+        }}
+    }
+
     asmsub  reset_system()  {
         ; Soft-reset the system back to initial power-on Basic prompt.
         ; TODO
@@ -248,27 +264,38 @@ save_SCRATCH_ZPWORD2	.word  0
 
     asmsub exit(ubyte returnvalue @A) {
         ; -- immediately exit the program with a return code in the A register
-        ;    TODO where to store A as exit code?
         %asm {{
+            sta  cleanup_at_exit._exitcode
             ldx  prog8_lib.orig_stackpointer
             txs
-            rts		; return to original caller
+            jmp  cleanup_at_exit
         }}
     }
 
     asmsub exit2(ubyte resulta @A, ubyte resultx @X, ubyte resulty @Y) {
         ; -- immediately exit the program with result values in the A, X and Y registers.
-        ;    TODO where to store A,X,Y as exit code?
         %asm {{
-            jmp  exit
+            sta  cleanup_at_exit._exitcode
+            stx  cleanup_at_exit._exitcodeX
+            sty  cleanup_at_exit._exitcodeY
+            ldx  prog8_lib.orig_stackpointer
+            txs
+            jmp  cleanup_at_exit
         }}
     }
 
     asmsub exit3(ubyte resulta @A, ubyte resultx @X, ubyte resulty @Y, bool carry @Pc) {
         ; -- immediately exit the program with result values in the A, X and Y registers, and the Carry flag in the status register.
-        ;    TODO where to store A,X,Y,Carry as exit code?
         %asm {{
-            jmp  exit
+            sta  cleanup_at_exit._exitcode
+            lda  #0
+            rol  a
+            sta  cleanup_at_exit._exitcodeCarry
+            stx  cleanup_at_exit._exitcodeX
+            sty  cleanup_at_exit._exitcodeY
+            ldx  prog8_lib.orig_stackpointer
+            txs
+            jmp  cleanup_at_exit
         }}
     }
 

compiler/res/prog8lib/prog8_lib.asm

@@ -5,6 +5,26 @@
 orig_stackpointer	.byte  0	; stores the Stack pointer register at program start
 
 
+program_startup_clear_bss    .proc
+	; this is always ran first thing from the start routine to clear out the BSS area
+	.if  prog8_bss_section_size>0
+		; reset all variables in BSS section to zero
+		lda  #<prog8_bss_section_start
+		ldy  #>prog8_bss_section_start
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldx  #<prog8_bss_section_size
+		ldy  #>prog8_bss_section_size
+		lda  #0
+		jsr  prog8_lib.memset
+	.endif
+		clv
+		clc
+		rts
+		.pend
+
+
+
 read_byte_from_address_in_AY_into_A	.proc
 		sta  P8ZP_SCRATCH_W2
 		sty  P8ZP_SCRATCH_W2+1

docs/source/todo.rst

@@ -1,7 +1,7 @@
 TODO
 ====
 
-Can we move the asm init code that is injected into the start() subroutine, to init_system_phase2 instead?
+Shouldn't RAW output target have some initialization logic too? Does it even clear the variables/bss etc?
 
 Doc improvements: some short overview for people coming from other programming languages like C:
   tell something about prog8 not having function overloading, max 16 bit (u)word integer as native type (and floats sometimes),

examples/test.p8

@@ -1,16 +1,13 @@
 %import textio
-%import floats
+%zeropage dontuse
-%zeropage basicsafe
+%option no_sysinit
 
 main {
+    uword @shared variable
     sub start() {
-        float fl = 5.23
+        txt.print("hello!\n")
-        fl = floats.ceil(fl)
+        txt.print_uw(variable)
-        floats.print(fl)
-        txt.nl()
-        fl = 5.23
-        fl = floats.floor(fl)
-        floats.print(fl)
         txt.nl()
+        sys.exit3(1,2,3,false)
     }
 }