[std.fmt] Added parsing support for f80

[hmcty]

Resolves: #19263

Test plan:

• zig test lib/std/fmt/parse_float.zig passes locally with additional f80 unit tests
• CI passes

[tiehuis]

Looks pretty good.

Can you remove this (no longer needed) check here for float round-tripping? then I will trigger the CI:

zig/lib/std/fmt/format_float.zig

Line 1524 in cb308ba

if (@bitSizeOf(T) != 80) {

[hmcty]

Addressed all comments @tiehuis

[tiehuis]

Windows round trip error:

C:\Users\ci\george2\_work\zig\zig\build-release\zig-local-cache\o\ef0547664f7b4931546bf402c80a8059\test.exe --listen=- 
test
+- test-std
   +- run test std-x86_64-windows.win11_ge...win11_ge-gnu-skylake-Debug 2657/2724 passed, 1 failed, 66 skipped
error: 'fmt.format_float.test.format f80' failed: expected 907682844368439810595840, found 907682844368439810596864
C:\Users\ci\george2\_work\zig\zig\lib\std\testing.zig:93:17: 0xe829e3 in expectEqualInner__anon_35380 (test.exe.obj)
                return error.TestExpectedEqual;
                ^
C:\Users\ci\george2\_work\zig\zig\lib\std\fmt\format_float.zig:1530:9: 0x12db79a in check__anon_46210 (test.exe.obj)
        try std.testing.expectEqual(value_bits, o_bits);
        ^
C:\Users\ci\george2\_work\zig\zig\lib\std\fmt\format_float.zig:1655:5: 0x12dcd86 in test.format f80 (test.exe.obj)
    try check(f80, -2.109808898695963e16, "-2.109808898695963e16");
    ^

I'll have a look during the week and see if I can reproduce via wine.

---

Linux-debug segfault as well to look at. I'll rerun given the rebase and see if this has persisted. This looks resolved after the rebase.

From https://github.com/ziglang/zig
   bf588f67d..c40708a2c  master     -> origin/master
+ git fetch --tags
+ git clean -fd
+ rm -rf zig-out
+ cc -o bootstrap bootstrap.c
+ ./bootstrap
cc -o zig-wasm2c stage1/wasm2c.c -O2 -std=c99
./zig-wasm2c stage1/zig1.wasm zig1.c
cc -o zig1 zig1.c stage1/wasi.c -std=c99 -Os -lm
./zig1 lib build-exe -ofmt=c -lc -OReleaseSmall --name zig2 -femit-bin=zig2.c -target x86_64-linux --dep build_options --dep aro --mod root src/main.zig --mod build_options config.zig --mod aro lib/compiler/aro/aro.zig
./zig1 lib build-obj -ofmt=c -OReleaseSmall --name compiler_rt -femit-bin=compiler_rt.c -target x86_64-linux --dep build_options --mod root lib/compiler_rt.zig --mod build_options config.zig
cc -o zig2 zig2.c compiler_rt.c -std=c99 -O2 -fno-stack-protector -Istage1 -Wl,-z,stack-size=0x10000000 -pthread
+ ./zig2 build -Dno-lib
+ ./zig-out/bin/zig test test/behavior.zig
Segmentation fault

[tiehuis]

Just noting I hit #17535 when trying to test under wine.

[tiehuis]

I wasn't able to diagnose a fix on the windows CI failures so have added a skip for the round-trip tests for now for this target, and will add an issue noting the failure for future. I've manually rebased your commits and will merge when CI passes.