# Library folders — implementation note

**Status: implemented (2026-10-24).**

The former aggregate `stdlib/` is retired.  Libraries now live in
dialect folders:

| Folder | Contents |
| --- | --- |
| `runtime/syslib/` | shared runtime: `SysShim`, `FileIO`, `SysExceptions`, `Utf8` |
| `lib/common/` | `CharClass`, `Math`, `Storage`, `Strings`, `SysIO` |
| `lib/pim/` | `FpuIO`, `InOut`, `NumberIO`, `RealInOut`, `StrIO` |
| `lib/iso/` | ISO 10514-1: `IOChan`, `StreamFile`, `TextIO`, `STextIO`, `SWholeIO`, `SRealIO`, `WholeIO`, `RealIO`, `LongIO`, `LongWholeIO`, `Conversions`, `ConvTypes`, `IOConsts`, `SIOResult`, `RealStr`, `WholeStr`, `LongStr`, `LongMath`, `Files`, `ProgramArgs`, `SysClock`, `TERMINATION`, `EXCEPTIONS`, `M2EXCEPTION` |
| `lib/gm2/` | optional gm2 compatibility: `DynamicStrings`, `StdIO`, `SysStorage`, `TimeString`, `wrapc`, `wrapclock`, `wraptime` |

`lib/common` holds modules whose V3 implementation is genuinely shared;
`Strings` is included there because it is a classic descriptor-string
library used by both dialect tests.  `lib/gm2` is not a dialect: it is
an optional compatibility set used by the corpus/tests.  Do not mix
`lib/pim` and `lib/iso` in one session.

## Build and test selection

- `M2make --dialect pim|iso|gm2` adds `lib/<dialect>`, `lib/common`,
  `lib/gm2` and `runtime/syslib` to module resolution.
- `tools/v3-corpus/corpus.sh` chooses `lib/iso` for paths containing
  `/iso/`, otherwise `lib/pim`, and adds `lib/common`, `lib/gm2` and
  `runtime/syslib`.  `V3_LIBS` remains an explicit override.
- `compiler/run_tests.sh` lists library files explicitly; all paths were
  migrated to `lib/<dialect>/...`.
- `bootstrap/fixpoint.sh` uses `-I lib/common` and `runtime/syslib` for
  the compiler (it imports `Strings`/`Storage` and the shared runtime).

The one-shot multi-file compilation model is unchanged; this is a
directory/build-selection change, not separate compilation.