97 lines
4.3 KiB
Markdown
97 lines
4.3 KiB
Markdown
---
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layout: soml
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title: Register Level Debugger / simulator
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---
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## Views
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From left to right there are several views showing different data and controls.
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All of the green boxes are in fact pop-up menus and can show more information.
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Most of these are implemented as a single class with the name reflecting what part.
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I wrote 2 base classes that handle element generation (ie there is hardly any html involved, just elements)
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### Switch view
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Top left at the top is a little control to switch files.
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The files need to be in the repository, but at least one can have several and switch between
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them without stopping the debugger.
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Parsing is the only thing that opal chokes on, so the files are parsed by a server script and the
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ast is sent to the browser.
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### Classes View
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The first column on the left is a list of classes in the system. Like on all boxes one can hover
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over a name to look at the class and it's instance variables (recursively)
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### Source View
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Next is a view of the Soml source. The Source is reconstructed from the ast as html.
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Soml (Salama object machine language) is is a statically typed language,
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maybe in spirit close to c++ (without the c). In the future Salama will compile ruby to soml.
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While stepping through the code, those parts of the code that are active get highlighted in blue.
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Currently stepping is done only in register instructions, which means that depending on the source
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constructs it may take many steps for the cursor to move on.
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Each step will show progress on the register level though (next view)
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### Register Instruction view
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Salama defines a register machine level which is quite close to the arm machine, but with more
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sensible names. It has 16 registers (below) and an instruction set that is useful for Soml.
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Data movement related instruction implement an indexed get and set. There is also Constant load and
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integer operators and off course branches.
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Instructions print their name and used registers r0-r15.
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The next instruction to be executed is highlighted in blue. A list of previous instructions is shown.
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One can follow the effect of instruction in the register view below.
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### Status View
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The last view at the top right show the status of the machine (interpreter to be precise), the
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instruction count and any stdout
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Current controls include stepping and three speeds of running the program.
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- Next (green button) will execute exactly one instruction when clicked. Mostly useful when
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debugging the compiler, ie inspecting the generated code.
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- Crawl (first blue button) will execute at a moderate speed. One can still follow the
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logic at the register level
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- Run (second blue button) runs the program at a higher speed where register instruction just
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whizz by, but one can still follow the source view. Mainly used to verify that the source executes
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as expected and also to get to a specific place in the program (in the absence of breakpoints)
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- Wizz (third blue button) makes the program run so fast that it's only useful function is to
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fast forward in the code (while debugging)
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### Register view
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The bottom part of the screen is taken up by the 16 register. As we execute an object oriented
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language, we show the object contents if it is an object (not an integer) in a register.
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The (virtual) machine only uses objects, and specifically a linked list of Message objects to
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make calls. The current message is always in register 0 (analgous to a stack pointer).
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All other registers are scratch for statement use.
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In Soml expressions compile to the register that holds the expressions value and statements may use
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all registers and may not rely on anything other than the message in register 0.
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The Register view is now greatly improved, especially in it's dynamic features:
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- when the contents update the register obviously updates
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- when the object that the register holds updates, the new value is shown immediately
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- hovering over a variable will **expand that variable** .
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- the hovering works recursively, so it is possible to drill down into objects for several levels
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The last feature of inspecting objects is show in the screenshot. This makes it possible
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to very quickly verify the programs behaviour. As it is a pure object system , all data is in
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objects, and all objects can be inspected.
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