std.debug: reorg and clarify API goals #20908
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This code has the hard-coded goal of supporting the executable's own debug information and makes design choices along that goal, such as memory-mapping the inputs, using dl_iterate_phdr, and doing conditional compilation on the host target. A more general-purpose implementation of debug information may be able to share code with this, but there are some fundamental incompatibilities. For example, the "SelfInfo" implementation wants to avoid bloating the binary with PDB on POSIX systems, and likewise DWARF on Windows systems, while a general-purpose implementation needs to support both PDB and DWARF from the same binary. It might, for example, inspect the debug information from a cross-compiled binary. `SourceLocation` now lives at `std.debug.SourceLocation` and is documented. Deprecate `std.debug.runtime_safety` because it returns the optimization mode of the standard library, when the caller probably wants to use the optimization mode of their own module. `std.pdb.Pdb` is moved to `std.debug.Pdb`, mirroring the recent extraction of `std.debug.Dwarf` from `std.dwarf`. I have no idea why we have both Module (with a Windows-specific definition) and WindowsModule. I left some passive aggressive doc comments to express my frustration.
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After this commit: `std.debug.SelfInfo` is a cross-platform abstraction for the current executable's own debug information, with a goal of minimal code bloat and compilation speed penalty. `std.debug.Dwarf` does not assume the current executable is itself the thing being debugged, however, it does assume the debug info has the same CPU architecture and OS as the current executable. It is planned to remove this limitation.
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...which have a ucontext_t but not a PC register. The current stack unwinding implementation does not yet support this architecture. Also fix name of `std.debug.SelfInfo.openSelf` to remove redundancy. Also removed this hook into root providing an "openSelfDebugInfo" function. Sorry, this debugging code is not of sufficient quality to offer a plugin API right now.
There are two concepts here: one for whether dwarf supports unwinding on that target, and another for whether the Zig standard library implements it yet.
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With this changeset:
std.debug.SelfInfois a cross-platform abstraction for the current executable's own debug information, with a goal of minimal code bloat and compilation speed penalty.std.debug.Dwarfno longer assumes the current executable is itself the thing being debugged, however, it does assume the debug info has the same CPU architecture and OS as the current executable. I plan to remove this limitation is a future enhancement.Unwind tables are emitted more often by default because the logic uses whether dwarf supports unwinding rather than whether the Zig standard library supports unwinding.