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*WIP* error return trace proof of concept #684
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instead of being last. This increases the chances that it can remain in the same register between calls.
Just out of curiosity... why does the deepest entry in the stack trace have a source location pointing at the |
Yes it should point at the next line. There's either an issue with zig's dwarf code, LLVM's debug info code, or the way we specify debug info for the return statement. I'll look into it. |
* error return tracing is disabled in release-fast mode * add @errorReturnTrace * zig build API changes build return type from `void` to `%void` * allow `void`, `noreturn`, and `u8` from main. closes #535
This was referenced Jan 15, 2018
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There is some cleanup needed before this is ready to merge. But this solves issue #651.
As a demonstration, watch what happens when I mischeviously insert a subtle bug deep in the standard library:
If the 2nd character of the program we want to execute is
n
then return ProcessNotFound. Yikes, imagine trying to find this bug.As it so happens, when we run
zig build
it will run/nix-store/.../llvm-config
on my computer, so we can observe this getting triggered:I get this beautiful output:
BOOM! We caught the culprit red-handed. Nice try!!
(here is the output in text form)
Notice that if we were able to strip out these 2 stack frames (which I know how we can accomplish)...
...then the error return trace flows directly into the stack trace. That is, the
return result
at build.zig:202 returns exactly to the beginning of the stack trace - thecatch unreachable
at build.zig:50 which is what triggered the "attempt to unwrap error".