Add Natvis visualiser and debuginfo tests for `f128` by beetrees · Pull Request #161777 · rust-lang/rust

beetrees · 2026-08-25T17:40:38Z

To render f128s in debuggers on MSVC targets, this PR changes the compiler to output f128s as struct f128 { low_bits: u64, high_bits: u64 }, and includes a Natvis visualiser that displays the float in hexdecimal format (similar to the LowerHex impl in #160626), as unlike f16 there's no larger supported float format to convert to and trying to write a float to decimal string converter in Natvis didn't seem practical. gdb, lldb and cdb tests are also included for f128, although gdb does not yet correctly identify the float format.

I did consider also displaying a double approximation of the f128 (as the debugger will convert that to a decimal string) but decided against it as f64 has a significantly smaller exponent range too (meaning very large or small f128s couldn't have an approximation anyway) and cdb and WinDbg both seem to round all floating-point numbers to 6 decimal places, meaning the displayed number is (double) rounded even further than f64 precision and is useless for tiny values.

Closes #121837
Tracking issue: #116909

rustbot · 2026-08-25T19:20:19Z

r? @JohnTitor

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beetrees · 2026-08-25T19:22:21Z

cc MSVC target maintainers: @ChrisDenton @dpaoliello @Fulgen301 @lambdageek @sivadeilra @wesleywiser

beetrees · 2026-08-25T19:29:06Z

(Given this touches debuginfo tests this should probably get a bors try x86_64-msvc-* i686-msvc-* aarch64-msvc-* aarch64-apple-*.)

folkertdev · 2026-08-25T19:57:23Z

@bors try jobs=x86_64-msvc-,i686-msvc-,aarch64-msvc-,aarch64-apple-

folkertdev · 2026-08-25T19:58:06Z

@bors try jobs=x86_64-msvc-,i686-msvc-,aarch64-msvc-,aarch64-apple-

Add Natvis visualiser and debuginfo tests for `f128` try-job: x86_64-msvc-* try-job: i686-msvc-* try-job: aarch64-msvc-* try-job: aarch64-apple-*

rust-bors · 2026-08-25T23:07:38Z

💔 Test for 816a2f0 failed: CI. Failed jobs:

try - aarch64-apple-1 (web logs, enhanced plaintext logs)
try - aarch64-apple-macos-26-1 (web logs, enhanced plaintext logs)

beetrees · 2026-08-26T10:07:31Z

According to the table on Wikipedia, there isn't any Xcode versions yet with LLDB 22 or later, so I've ignored the f128 debuginfo tests on Apple for now and left a FIXME.

folkertdev · 2026-08-26T10:08:43Z

@bors try jobs=x86_64-msvc-,i686-msvc-,aarch64-msvc-,aarch64-apple-

Add Natvis visualiser and debuginfo tests for `f128` try-job: x86_64-msvc-* try-job: i686-msvc-* try-job: aarch64-msvc-* try-job: aarch64-apple-*

rust-bors · 2026-08-26T12:56:44Z

☀️ Try build successful (CI)
Build commit: d79cce8 (d79cce855e6f305d9b8796f97b79e09fb0a5c022)
Base parent: 3ffb26f (3ffb26fbf5bf232cf59e314e75ea325973f4f583)

beetrees · 2026-08-26T14:40:08Z

@rustbot review

JohnTitor

Looks good! I'm not going to r+ just in case you want to wait for another look from the target maintainers. Ohterwise r=me

View changes since this review

rust-bors · 2026-09-18T17:27:59Z

This pull request was unapproved.

This PR was contained in a rollup (#162973), which was unapproved.

View changes since this unapproval

rust-bors · 2026-09-18T18:05:12Z

⚠️ A new commit b7bad07da0564a861c8ffcbeb290d4409f5cb937 was pushed.

This PR was contained in a rollup (#162973), which was closed.

beetrees · 2026-09-18T18:14:09Z

Test fails locally on i686-unknown-linux-gnu - I think GDB can't find any 16-byte float type to represent it internally so can't even display the DWARF type name. Since GDB doesn't have proper f128 support yet and the type names working is more of a coincidence, I've replaced the failing checks with FIXMEs.

@bors try jobs=test-i686-gnu-nopt-1

Add Natvis visualiser and debuginfo tests for `f128` try-job: test-i686-gnu-nopt-1

rust-bors · 2026-09-18T19:57:20Z

☀️ Try build successful (CI)
Build commit: fd84d0d (fd84d0de4842e4d20e8d41134ffe0b41ef0060c6)
Base parent: 420ed2a (420ed2a0c3d7225b1744266fd884d431b4d8cfe0)

beetrees · 2026-09-18T20:33:37Z

@rustbot review

JohnTitor · 2026-09-19T00:53:02Z

@bors r+

rust-bors · 2026-09-19T00:53:05Z

📌 Commit b7bad07 has been approved by JohnTitor

It is now in the queue for this repository.

Add Natvis visualiser and debuginfo tests for `f128` To render f128s in debuggers on MSVC targets, this PR changes the compiler to output `f128`s as `struct f128 { low_bits: u64, high_bits: u64 }`, and includes a Natvis visualiser that displays the float in hexdecimal format (similar to the `LowerHex` impl in rust-lang#160626), as unlike `f16` there's no larger supported float format to convert to and trying to write a float to decimal string converter in Natvis didn't seem practical. gdb, lldb and cdb tests are also included for `f128`, although gdb does not yet correctly identify the float format. I did consider also displaying a `double` approximation of the `f128` (as the debugger will convert that to a decimal string) but decided against it as `f64` has a significantly smaller exponent range too (meaning very large or small `f128`s couldn't have an approximation anyway) and `cdb` and `WinDbg` both seem to round all floating-point numbers to 6 decimal places, meaning the displayed number is (double) rounded even further than `f64` precision and is useless for tiny values. Closes rust-lang#121837 Tracking issue: rust-lang#116909

Rollup of 18 pull requests Successful merges: - #162499 (`rustc_codegen_gcc` subtree update) - #161424 (implement `VaArgSafe` for `f128`) - #161777 (Add Natvis visualiser and debuginfo tests for `f128`) - #162506 (Avoid suggesting imports of traits declared inside fn bodies) - #162591 (Move parse error recovery for expression operators "out of line" & refactor in the area) - #162669 ([rustdoc] Correctly handle intra-doc links on inlined same item with different names) - #162733 (Add useful APIs to `Unique(Arc|Rc)`) - #162913 (Refactor LivenessResults into LivenessComputation, without typeck) - #162950 (More AST lowering cleanups) - #162964 (Update `browser-ui-test` version to `0.25.2`) - #162979 (mark `f128` as reliable on `powerpc64` with `+vsx`) - #161743 (Add performance notes for the floating-point round method) - #162797 (yeet AliasConstKind::opt_def_id) - #162836 (Ping T-libs-ping instead of T-libs-fcp for backports) - #162873 (Adjust `bug!`/`span_bug!` emission) - #162875 (Add .seek_read_exact(), .seek_write_all() to std::os::windows::fs::FileExt) - #162956 (Add missing `#[repr(C)]` in UI, codegen and assembly tests) - #162981 (rustc-dev-guide subtree update) Failed merges: - #162177 (Properly implement the gpu-kernel ABI for amdgpu)

Add Natvis visualiser and debuginfo tests for `f128` To render f128s in debuggers on MSVC targets, this PR changes the compiler to output `f128`s as `struct f128 { low_bits: u64, high_bits: u64 }`, and includes a Natvis visualiser that displays the float in hexdecimal format (similar to the `LowerHex` impl in rust-lang#160626), as unlike `f16` there's no larger supported float format to convert to and trying to write a float to decimal string converter in Natvis didn't seem practical. gdb, lldb and cdb tests are also included for `f128`, although gdb does not yet correctly identify the float format. I did consider also displaying a `double` approximation of the `f128` (as the debugger will convert that to a decimal string) but decided against it as `f64` has a significantly smaller exponent range too (meaning very large or small `f128`s couldn't have an approximation anyway) and `cdb` and `WinDbg` both seem to round all floating-point numbers to 6 decimal places, meaning the displayed number is (double) rounded even further than `f64` precision and is useless for tiny values. Closes rust-lang#121837 Tracking issue: rust-lang#116909

…uwer Rollup of 22 pull requests Successful merges: - #163001 (Temporarily disable `test-x86_64-fuchsia`) - #162880 (Mini optimization in `rustc_hir_typeck::upvar::restrict_precision_for_drop_types`) - #161424 (implement `VaArgSafe` for `f128`) - #161777 (Add Natvis visualiser and debuginfo tests for `f128`) - #162506 (Avoid suggesting imports of traits declared inside fn bodies) - #162591 (Move parse error recovery for expression operators "out of line" & refactor in the area) - #162669 ([rustdoc] Correctly handle intra-doc links on inlined same item with different names) - #162733 (Add useful APIs to `Unique(Arc|Rc)`) - #162913 (Refactor LivenessResults into LivenessComputation, without typeck) - #162924 (Remove applying inline attributes at the callsite) - #162940 (Use spawned `SBDebugger` instance) - #162950 (More AST lowering cleanups) - #162964 (Update `browser-ui-test` version to `0.25.2`) - #162979 (mark `f128` as reliable on `powerpc64` with `+vsx`) - #161743 (Add performance notes for the floating-point round method) - #162797 (yeet AliasConstKind::opt_def_id) - #162836 (Ping T-libs-ping instead of T-libs-fcp for backports) - #162873 (Adjust `bug!`/`span_bug!` emission) - #162956 (Add missing `#[repr(C)]` in UI, codegen and assembly tests) - #162971 (libtest harness: avoid 'extern crate test' with custom runner) - #162981 (rustc-dev-guide subtree update) - #162985 (Error on invalid placements for unstable attributes)

Rollup merge of #161777 - beetrees:f128-debuginfo, r=JohnTitor Add Natvis visualiser and debuginfo tests for `f128` To render f128s in debuggers on MSVC targets, this PR changes the compiler to output `f128`s as `struct f128 { low_bits: u64, high_bits: u64 }`, and includes a Natvis visualiser that displays the float in hexdecimal format (similar to the `LowerHex` impl in #160626), as unlike `f16` there's no larger supported float format to convert to and trying to write a float to decimal string converter in Natvis didn't seem practical. gdb, lldb and cdb tests are also included for `f128`, although gdb does not yet correctly identify the float format. I did consider also displaying a `double` approximation of the `f128` (as the debugger will convert that to a decimal string) but decided against it as `f64` has a significantly smaller exponent range too (meaning very large or small `f128`s couldn't have an approximation anyway) and `cdb` and `WinDbg` both seem to round all floating-point numbers to 6 decimal places, meaning the displayed number is (double) rounded even further than `f64` precision and is useless for tiny values. Closes #121837 Tracking issue: #116909

…uwer Rollup of 22 pull requests Successful merges: - rust-lang/rust#163001 (Temporarily disable `test-x86_64-fuchsia`) - rust-lang/rust#162880 (Mini optimization in `rustc_hir_typeck::upvar::restrict_precision_for_drop_types`) - rust-lang/rust#161424 (implement `VaArgSafe` for `f128`) - rust-lang/rust#161777 (Add Natvis visualiser and debuginfo tests for `f128`) - rust-lang/rust#162506 (Avoid suggesting imports of traits declared inside fn bodies) - rust-lang/rust#162591 (Move parse error recovery for expression operators "out of line" & refactor in the area) - rust-lang/rust#162669 ([rustdoc] Correctly handle intra-doc links on inlined same item with different names) - rust-lang/rust#162733 (Add useful APIs to `Unique(Arc|Rc)`) - rust-lang/rust#162913 (Refactor LivenessResults into LivenessComputation, without typeck) - rust-lang/rust#162924 (Remove applying inline attributes at the callsite) - rust-lang/rust#162940 (Use spawned `SBDebugger` instance) - rust-lang/rust#162950 (More AST lowering cleanups) - rust-lang/rust#162964 (Update `browser-ui-test` version to `0.25.2`) - rust-lang/rust#162979 (mark `f128` as reliable on `powerpc64` with `+vsx`) - rust-lang/rust#161743 (Add performance notes for the floating-point round method) - rust-lang/rust#162797 (yeet AliasConstKind::opt_def_id) - rust-lang/rust#162836 (Ping T-libs-ping instead of T-libs-fcp for backports) - rust-lang/rust#162873 (Adjust `bug!`/`span_bug!` emission) - rust-lang/rust#162956 (Add missing `#[repr(C)]` in UI, codegen and assembly tests) - rust-lang/rust#162971 (libtest harness: avoid 'extern crate test' with custom runner) - rust-lang/rust#162981 (rustc-dev-guide subtree update) - rust-lang/rust#162985 (Error on invalid placements for unstable attributes)

beetrees force-pushed the f128-debuginfo branch from b68bc57 to e9dc1bb Compare August 25, 2026 17:56

beetrees marked this pull request as ready for review August 25, 2026 19:20

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 25, 2026

rustbot assigned JohnTitor Aug 25, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 25, 2026