On Thu, 16 Jan 2014 21:59:42 +0100, Greg Clayton <[email protected]>
wrote:
Just an idea anyway. I've been trying to see how to fit my (pascal)
language into lldb, but due to the way it's designed (the compiler),
it's not feasible to compile a single expression/method into IR and
transfer it over (Besides that, it's written in another language than
c++).
That means creating your own expression parser that won't be language
compliant, and is the whole reason we are generating clang AST types
from DWARF: to avoid having top write an expression parser when the
compiler is the best expression parser we could ever have.
Things we can do in our expression parser that other debuggers can't:
- create expression local variables ("int i = 12; int j = 23; i+j")
- use flow control (if/then/else, while, do/while, switch, etc)
- create types and use them in the expression ("struct foo { int x;
float y; }; foo = { 123, 2.3 }; foo")
- much much more!
So the one great thing we can do, is just re-compile clang and we get
all the new language features (C++11, etc) for free. If we maintain a
separate expression parser that isn't in the compiler, then you do all
this work manually. We also use the clang expression parser to avoid
running into errors when calling functions as it is very complex to
figure out which arguments go where in expressions. When we call a
function in the JIT, we give clang a structure in memory that contains
all arguments and let it call the function correctly. So there is way
too much stuff we would need to re-code, so the hard fight to translate
DWARF into compiler types ends up being well worth it on the long run.
Hrmm true yes. Maybe there could be a way to generate clang expressions
from code (not string) and accessing the "clang" type info tables the
clang expressions have access to? So languages could start with (or stay
with?) using clang structures as a fairly simple api for expression
evaluators?
--
Carlo Kok
RemObjects Software
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