fix!(codegen): initialize function outputs and omitted arguments (1.0.x) - #1959
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Problem: When a call left out an argument, the compiler passed the contents of a stack slot that nothing had written, so the callee saw whatever the previous call had left there. A VAR_OUTPUT of a function or method also started every call with the caller's current value, so a path that did not assign the output leaked that value back. Solution: An argument that is left out, or written empty, carries the declared default or zero. Outputs of functions and methods are initialized like local variables at the start of each call: codegen zero-fills them through the caller's address and the init lowering adds the constructor call and initializer assignment. Variable length array outputs keep the caller's bounds. Non-constant output initializers such as ADR(THIS^) are left to the lowered initializer. Cherry-picked from the master PR for PRG-4940. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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is this really breaking? (fix!) |
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I wasn't 100% sure so I asked claude to flag it, different results are returned on a recompile of the same code. I think this is technically breaking but the returned results were wrong before... so I dunno. I don't mind removing it (the |
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Problem: When a call left out an argument, the compiler passed the contents of a stack slot that nothing had written, so the callee saw whatever the previous call had left there. A VAR_OUTPUT of a function or method also started every call with the caller's current value, so a path that did not assign the output leaked that value back.
Solution: An argument that is left out, or written empty, carries the declared default or zero. Outputs of functions and methods are initialized like local variables at the start of each call: codegen zero-fills them through the caller's address and the init lowering adds the constructor call and initializer assignment. Variable length array outputs keep the caller's bounds. Non-constant output initializers such as ADR(THIS^) are left to the lowered initializer.
Cherry-picked from the master PR for PRG-4940.