rudimentary Error Technology™

2 files changed, 61 insertions, 8 deletions

diff --git a/readme.md b/readme.md
index 9257664..4613d21 100644
--- a/readme.md
+++ b/readme.md
@@ -23,16 +23,22 @@ store the 64 bit value u into the memory address a.
 ### `#tib   ( -- a )`
 variable containing the amount of characters in the input buffer.
 
-### `(header)   ( a u -- xt )`
-create a dictionary header for a word named the provided string.
-this word does not set the code field.
-this word returns an incompleted xt and does not update latest.
-
 ### `(   ( -- ) IMMEDIATE`
 start a comment which lasts until the next closed bracket.
 if the unclosed bracket in the description above bothers you,
 have a closing bracket: ).
 
+### `(0handler)   ( -- )`
+the very early error handler, which simply quits the program.
+
+### `(execute)   ( a -- )`
+call the function at the address.
+
+### `(header)   ( a u -- xt )`
+create a dictionary header for a word named the provided string.
+this word does not set the code field.
+this word returns an incompleted xt and does not update latest.
+
 ### `*   ( u1 u2 -- u)`
 multiply u1 and u2.
 
@@ -143,6 +149,10 @@ remove the two topmost values from the stack.
 ### `2dup   ( u1 u2 -- u1 u2 u1 u2 )`
 duplicate the two topmost values on the stack.
 
+### `abort   ( -- )`
+call the error handler
+(the address of which is in the variable `handler`)
+
 ### `and   ( u1 u2 -- u )`
 perform bitwise AND on u1 and u2.
 
@@ -209,6 +219,9 @@ marks the u bytes starting at address a as executable.
 this is used primarily to mark the program break,
 which is used as the user memory space.
 
+### `execute   ( xt -- )`
+call the word xt.
+
 ### `find   ( a u -- a u 0 | xt -1 )`
 look in the dictionary for the word a (of u characters).
 a zero is returned along with the original given string
@@ -218,6 +231,9 @@ its xt is returned along with the true flag.
 ### `grow   ( u -- )`
 grows, and marks as executable, the user memory space by u bytes.
 
+### `handler   ( -- a )`
+variable containing the address of the current error handler.
+
 ### `here   ( -- a )`
 yields the address of the first available byte in user memory.
 
diff --git a/sanctuary.s b/sanctuary.s
index 0d35337..53749cc 100644
--- a/sanctuary.s
+++ b/sanctuary.s
@@ -1,15 +1,26 @@
 ; sanctuary
 
 ; macros {{{
-; TODO: error handling (once i add that)
+; the error handling feels slow but i dont know a better way
+; todo at some point make these use actual error codes
 %macro pspush 1
 	lea r15, [r15-8]
 	mov qword [r15], %1
+
+	cmp r15, wstk_b
+	jge %%ok
+	call abort
+	%%ok:
 %endmacro
 
 %macro pspop 1
 	mov %1, qword [r15]
 	lea r15, [r15+8]
+
+	cmp r15, wstk
+	jle %%ok
+	call abort
+	%%ok:
 %endmacro
 
 %define s_latest 0
@@ -58,8 +69,8 @@
 %assign init_brk	0x9c400
 
 section .bss
-resq 4091
-wstk: resq 1
+wstk_b:	resq 4091
+wstk:	resq 1
 
 section .text
 global _start
@@ -502,6 +513,16 @@ defcode "char", char, 0
 	pspush r11
 	ret
 
+defcode "(execute)", do_execute, 0
+	pspop r11
+	call r11
+	ret
+
+defcode "execute", execute, 0
+	call to_body
+	call do_execute
+	ret
+
 ; number {{{
 defcode "number", number, 0 ; ( c-addr u -- ?n flag )
 	pspop r11 ; u
@@ -965,6 +986,21 @@ defcode "?branch", q_branch, 0
 	mov qword [here], r12
 	ret
 
+; error handling {{{
+; default error handler, because we don't have QUIT yet
+; it just Exits with exit code 1
+defcode "(0handler)", do_0handler, 0
+	mov rdi, 1
+	mov rax, __NR_exit
+	syscall
+	ret
+
+defcode "abort", abort, 0
+	mov r11, qword [handler]
+	call r11
+	ret
+; }}}
+
 ; TEMPORARY WONKY DEBUGGING FUNCTIONS {{{
 ; .s {{{
 defcode ".s", dots, 0
@@ -1024,6 +1060,7 @@ defvar "dp$", dp$, 0, 0
 defvar "tib", tib, 0, initfile
 defvar "#tib", n_tib, 0, initlen
 defvar ">in", to_in, 0, 0
+defvar "handler", handler, 0, do_0handler
 defvar "latest", latest, 0, lfa_latest
 
 initfile: incbin "sanctuary.fs"