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Arguments passed as ScalarPairs do not work correctly with Windows debuggers #88625

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wesleywiser opened this issue Sep 3, 2021 · 0 comments · Fixed by #88629
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Arguments passed as ScalarPairs do not work correctly with Windows debuggers #88625

wesleywiser opened this issue Sep 3, 2021 · 0 comments · Fixed by #88629
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. O-windows-msvc Toolchain: MSVC, Operating system: Windows

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Arguments passed via the ScalarPair abi cannot be correctly inspected via WinDbg or VS debuggers. This occurs because the platform debuggers expect the type to passed via a pointer (as the abi says they should) and the debuggers are hardcoded to expect that.

Example:

fn foo(r: Range<usize>) {
    zzz(); // #break
}

Debuggers:

> dx r
r               : 0x14 [Type: core::ops::range::Range<usize> *]

(Notice the * in the type indicating the debugger expects to be looking at a pointer to the actual value, not it passed by value)

This is a more general version of #81894 which #81898 fixed for &str and slices.
@wesleywiser wesleywiser added A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) O-windows-msvc Toolchain: MSVC, Operating system: Windows C-bug Category: This is a bug. labels Sep 3, 2021
@wesleywiser wesleywiser self-assigned this Sep 3, 2021
@wesleywiser wesleywiser mentioned this issue Sep 3, 2021
Merged
Manishearth added a commit to Manishearth/rust that referenced this issue Sep 12, 2021
@Manishearth
Rollup merge of rust-lang#88629 - wesleywiser:fix_debuginfo_for_scala…
666df67 
…rpair_params, r=oli-obk

Fix debuginfo for parameters passed via the ScalarPair abi on Windows

Mark all of these as locals so the debugger does not try to interpret
them as being a pointer to the value. This extends the approach used
in rust-lang#81898.

Fixes rust-lang#88625
@bors bors closed this as completed in 5fd6f3b Sep 22, 2021
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. O-windows-msvc Toolchain: MSVC, Operating system: Windows
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Fix debuginfo for parameters passed via the ScalarPair abi on Windows wesleywiser/rust
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