Soul of a tiny new machine. More thorough tests → More comprehensible and rewrite-friendly software → More resilient society.
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# Helper to check an array's bounds, and to abort if they're violated.
# Really only intended to be called from code generated by mu.subx.
== code
__check-mu-array-bounds: # index: int, elem-size: int, arr-size: int, function-name: (addr array byte), array-name: (addr array byte)
# . prologue
55/push-ebp
89/<- %ebp 4/r32/esp
# . save registers
50/push-eax
51/push-ecx
52/push-edx
# . not bothering saving ebx; it's only clobbered if we're going to abort
# ecx = arr-size
8b/-> *(ebp+0x10) 1/r32/ecx
# var overflow/edx: int = 0
ba/copy-to-edx 0/imm32
# var offset/eax: int = index * elem-size
8b/-> *(ebp+8) 0/r32/eax
f7 4/subop/multiply-eax-with *(ebp+0xc)
# check for overflow
81 7/subop/compare %edx 0/imm32
0f 85/jump-if-!= __check-mu-array-bounds:overflow/disp32
# check bounds
39/compare %eax 1/r32/ecx
0f 82/jump-if-unsigned< $__check-mu-array-bounds:end/disp32 # negative index should always abort
# abort if necessary
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "fn " 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x14) 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 ": offset " 3 0) # 3=cyan
(draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " is too large for array '" 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x18) 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "'" 3 0) # 3=cyan
(abort "")
# never gets here
$__check-mu-array-bounds:end:
# . restore registers
5a/pop-to-edx
59/pop-to-ecx
58/pop-to-eax
# . epilogue
89/<- %esp 5/r32/ebp
5d/pop-to-ebp
c3/return
__check-mu-array-bounds:overflow:
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "fn " 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x14) 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 ": offset to array '" 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x18) 3 0) # 3=cyan
(draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "' overflowed 32 bits" 3 0) # 3=cyan
(abort "")
# never gets here
__mu-abort-null-index-base-address:
(abort "null address in 'index'")
__mu-abort-null-get-base-address:
(abort "null address in 'get'")