35 lines
1.5 KiB
Markdown
35 lines
1.5 KiB
Markdown
# Deferred decisions
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Design decisions deliberately postponed, with enough context to pick them up
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again without re-deriving the analysis. Each entry records what is deferred,
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why, the options on the table, and the trigger that should reopen it.
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---
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## GOOBJ external (cross-package) symbol references
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**Status:** resolved (v0.29.0+, 2026-08-07).
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**Approach taken.** Instead of parsing the compiler's iexport data (which
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would have required either `golang.org/x/tools` or an in-house parser), the
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resolver reads the **GOOBJ data directly** from the target package's `.a`
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archive. The `.a` file contains a `_go_.o` member whose GOOBJ format is the
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same one gasm writes — the parser reuses the same layout (`blkSymdef`,
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`blkNonpkgdef`, the string table), so no new dependency was needed.
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**How it works.**
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1. `go list -json -export <pkg>` finds the target package's `.a` file.
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2. `extractGOOBJ` reads the ar archive, finds the `_go_.o` member, skips
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the `"go object …\n!\n"` preamble and parses the GOOBJ header.
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3. `goobjFile.symbols()` walks `blkSymdef` and `blkNonpkgdef` in definition
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order — the same order the linker uses — to build the symbol → index
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mapping.
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4. `resolveExternalSymbols` wires the resolved `{PkgIdx, SymIdx}` into the
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GOOBJ emission.
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The resolver is invoked automatically when `img.Externals` is non-empty; it
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runs `go list` as a subprocess (consistent with `toolchainObjectPreamble`
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which already calls `go tool asm`). All symbol data is cached per package
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for the lifetime of the GOOBJ emission.
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