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lib/fmt+test: add {n}-placeholder printf family

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Hare-shaped {} / {0} / {n:mods} parser + printf wrappers. APIs:
fprintf, fprintfln, fdprintf, fdprintfln, printf, printfln, errorfln,
fatalf, bsprintf. Parser handles indexed/positional placeholders,
alignment (- / default / =), pad-width, zero-pad (_05), radix (x X o
b), precision (.N for int pad / str trunc), sign markers (+, space),
and {{ / }} escape.

Internals: scandigits + scanmods drive a field-by-field dispatch into
formatfield, which inlines the field→formattable widen per-arm to
sidestep task #18 (24B return-by-value miscompile in for-loop
context). Render through formatraw + formatone over io.stream sinks.

formatone tail-pad uses a separate counter rather than mirroring
Hare's `?`-propagating loop: ww's memio.fixed returns partial-write
0 instead of errors::overflow, so the Hare shape would spin forever
on a full fixed buffer.

Deferred per drew's vet: asprintf/errorf (needs os.alloc, #16),
parametric width/precision dispatch (#16-family), float arm (#17),
log.printfln family wiring (#15).

Tests: 26 scenarios covering every placeholder shape, both arms of
fprintf's variadic dispatch (incl. bool/rune to pin #18 regression),
bsprintf overflow + width-against-full-buffer, closed-stream.
This commit is contained in:
Hojun-Cho
2026-05-16 00:45:30 +09:00
parent 10de5a5e0e
commit bb10ee73a4
4 changed files with 785 additions and 9 deletions
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Makefile
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@@ -113,7 +113,7 @@ $(BIN)/wwdump_ww: selfhost/cmd/wwdump/main.ww \
selfhost/cmd/wcc/cgen.ww selfhost/cmd/wcc/cgenexpr.ww \
selfhost/cmd/wcc/cgenstmt.ww selfhost/cmd/wcc/cgenutil.ww \
selfhost/cmd/wcc/cgendecl.ww \
lib/os/os.ww lib/strconv/strconv.ww lib/strings/strings.ww lib/ascii/ascii.ww lib/fmt/fmt.ww \
lib/os/os.ww lib/strconv/strconv.ww lib/strings/strings.ww lib/ascii/ascii.ww lib/io/io.ww lib/memio/memio.ww lib/fmt/fmt.ww \
$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
$(LIB)/libwwrt.a | $(BIN)
cd $(BIN) && ./ww build \
@@ -134,7 +134,7 @@ $(BIN)/w6c_ww: selfhost/cmd/w6c/main.ww \
selfhost/cmd/wcc/cgen.ww selfhost/cmd/wcc/cgenexpr.ww \
selfhost/cmd/wcc/cgenstmt.ww selfhost/cmd/wcc/cgenutil.ww \
selfhost/cmd/wcc/cgendecl.ww \
lib/os/os.ww lib/strconv/strconv.ww lib/strings/strings.ww lib/ascii/ascii.ww lib/fmt/fmt.ww \
lib/os/os.ww lib/strconv/strconv.ww lib/strings/strings.ww lib/ascii/ascii.ww lib/io/io.ww lib/memio/memio.ww lib/fmt/fmt.ww \
$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
$(LIB)/libwwrt.a | $(BIN)
cd $(BIN) && ./ww build \