cg_llvm: Avoid `as_c_char_ptr` in several places by Zalathar · Pull Request #163789 · rust-lang/rust

Zalathar · 2026-10-05T07:36:26Z

As noted in rustc_codegen_llvm::ffi:

Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing &str or &[u8] data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as *const c_uchar instead of *const c_char. Both pointer types have the same ABI, and using *const c_uchar avoids the need for an extra cast from *const u8 on the Rust side.

The helper method as_c_char_ptr exists to make that extra cast more type-safe, but it's nicer to not need it all.

In addition to making call sites a bit simpler, this adjustment also makes it harder to accidentally pass a nul-terminated string to a function expecting a pointer/length string, and vice-versa.

There should be no change to compiler output.

rustbot · 2026-10-05T07:36:30Z

Some changes occurred in compiler/rustc_codegen_llvm/src/debuginfo

cc @Walnut356

rustbot · 2026-10-05T07:36:33Z

r? @davidtwco

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hanna-kruppe

r=me with one question/nit for your consideration.

r? me @bors rollup

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hanna-kruppe · 2026-10-05T18:09:19Z

+            passes_after_enzyme.map(|s| s.as_ptr()).unwrap_or(std::ptr::null()),
+            passes_after_enzyme.map(|s| s.len()).unwrap_or(0),


Is there a reason for changing from map_or to map().unwrap_or()? I don't care strongly one way or another, but this code used map_or before and the debug info changes in the earlier commit preserved map_or, so this change stood out to me.

In the other cases I was just updating the call to as_c_char_ptr, so I didn’t even think about whether to change the enclosing map_or or not; I just left it as-is.

For this one I wanted to move the call site, so (after some intermediate edits) I rewrote the calls in the style that comes naturally to me, since I find map_or needlessly confusing.

hanna-kruppe · 2026-10-06T07:39:33Z

@bors r+

rust-bors · 2026-10-06T07:39:36Z

📌 Commit ae54544 has been approved by hanna-kruppe

It is now in the queue for this repository.

…uppe cg_llvm: Avoid `as_c_char_ptr` in several places As noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. The helper method `as_c_char_ptr` exists to make that extra cast more type-safe, but it's nicer to not need it all. In addition to making call sites a bit simpler, this adjustment also makes it harder to accidentally pass a nul-terminated string to a function expecting a pointer/length string, and vice-versa. There should be no change to compiler output.

JonathanBrouwer · 2026-10-06T09:50:08Z

@bors try jobs=test-various

rust-bors · 2026-10-06T09:50:15Z

⌛ Trying commit ae54544 with merge a4521af…

To cancel the try build, run the command @bors try cancel.

Workflow: https://github.com/rust-lang/rust/actions/runs/37445703108

cg_llvm: Avoid `as_c_char_ptr` in several places try-job: test-various

…uppe cg_llvm: Avoid `as_c_char_ptr` in several places As noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. The helper method `as_c_char_ptr` exists to make that extra cast more type-safe, but it's nicer to not need it all. In addition to making call sites a bit simpler, this adjustment also makes it harder to accidentally pass a nul-terminated string to a function expecting a pointer/length string, and vice-versa. There should be no change to compiler output.

…uwer Rollup of 13 pull requests Successful merges: - #163090 (Run LLDB debuginfo tests on `x86_64-pc-windows-msvc` in CI) - #163863 (use the type name instead of `Self` in constructor paths again) - #163864 (Remove CLAUDE.md) - #163877 (Add regression test for duplicated rustdoc search results between std and core) - #162000 (peel_transparent_wrappers only works on non-1ZST) - #163257 (abby DSL: sanity checks on forall where clauses) - #163348 (perf:cache FFI safety results in improper_ctypes lint) - #163768 (Move more `rustdoc-html` tests in the right location) - #163789 (cg_llvm: Avoid `as_c_char_ptr` in several places) - #163807 (Add `has_reliable_f16b` for Arm) - #163826 (Update books) - #163849 (ci: update to PowerShell 7.6.6) - #163870 (Add if-installed:auto:spellcheck to pre-push script)

…uppe cg_llvm: Avoid `as_c_char_ptr` in several places As noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. The helper method `as_c_char_ptr` exists to make that extra cast more type-safe, but it's nicer to not need it all. In addition to making call sites a bit simpler, this adjustment also makes it harder to accidentally pass a nul-terminated string to a function expecting a pointer/length string, and vice-versa. There should be no change to compiler output.

rust-bors · 2026-10-06T15:57:26Z

💥 Test timed out after 21600s

…uwer Rollup of 25 pull requests Successful merges: - #163090 (Run LLDB debuginfo tests on `x86_64-pc-windows-msvc` in CI) - #163806 (even more `tests/crashes` migration for `-Znext-solver`) - #162156 (add IBM f128 type) - #163508 (Document the `rustc_on_unimplemented` attribute.) - #163794 (Use `target_family = "wasm"` instead of `target_arch = "wasm32"`) - #163863 (use the type name instead of `Self` in constructor paths again) - #163864 (Remove CLAUDE.md) - #163877 (Add regression test for duplicated rustdoc search results between std and core) - #163916 (Shrink `PartialRes` and its alignment) - #149753 (On name resolution error in parameter list, suggest possible `const` typo and avoid unnecessary second error) - #152557 (Oneshot `is_ready`) - #157273 (Stabilize `optimize` attribute) - #162000 (peel_transparent_wrappers only works on non-1ZST) - #163257 (abby DSL: sanity checks on forall where clauses) - #163343 (`unit` and `[1 x unit]` layouts are incompatible on big-endian targets) - #163348 (perf:cache FFI safety results in improper_ctypes lint) - #163768 (Move more `rustdoc-html` tests in the right location) - #163778 (check is_indirect_first_projection when replacing in RefProp) - #163789 (cg_llvm: Avoid `as_c_char_ptr` in several places) - #163807 (Add `has_reliable_f16b` for Arm) - #163809 (Switch TLS implementation for wasi and bump SDK version to 34) - #163826 (Update books) - #163849 (ci: update to PowerShell 7.6.6) - #163869 (INSTALL.md: use UCRT64 instead of MINGW64 in MSYS2 section) - #163870 (Add if-installed:auto:spellcheck to pre-push script)

…uppe cg_llvm: Avoid `as_c_char_ptr` in several places As noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. The helper method `as_c_char_ptr` exists to make that extra cast more type-safe, but it's nicer to not need it all. In addition to making call sites a bit simpler, this adjustment also makes it harder to accidentally pass a nul-terminated string to a function expecting a pointer/length string, and vice-versa. There should be no change to compiler output.

…uwer Rollup of 24 pull requests Successful merges: - #163090 (Run LLDB debuginfo tests on `x86_64-pc-windows-msvc` in CI) - #163806 (even more `tests/crashes` migration for `-Znext-solver`) - #163508 (Document the `rustc_on_unimplemented` attribute.) - #163794 (Use `target_family = "wasm"` instead of `target_arch = "wasm32"`) - #163863 (use the type name instead of `Self` in constructor paths again) - #163864 (Remove CLAUDE.md) - #163877 (Add regression test for duplicated rustdoc search results between std and core) - #163916 (Shrink `PartialRes` and its alignment) - #149753 (On name resolution error in parameter list, suggest possible `const` typo and avoid unnecessary second error) - #152557 (Oneshot `is_ready`) - #157273 (Stabilize `optimize` attribute) - #162000 (peel_transparent_wrappers only works on non-1ZST) - #163257 (abby DSL: sanity checks on forall where clauses) - #163343 (`unit` and `[1 x unit]` layouts are incompatible on big-endian targets) - #163348 (perf:cache FFI safety results in improper_ctypes lint) - #163768 (Move more `rustdoc-html` tests in the right location) - #163778 (check is_indirect_first_projection when replacing in RefProp) - #163789 (cg_llvm: Avoid `as_c_char_ptr` in several places) - #163807 (Add `has_reliable_f16b` for Arm) - #163809 (Switch TLS implementation for wasi and bump SDK version to 34) - #163826 (Update books) - #163849 (ci: update to PowerShell 7.6.6) - #163869 (INSTALL.md: use UCRT64 instead of MINGW64 in MSYS2 section) - #163870 (Add if-installed:auto:spellcheck to pre-push script)

…uwer Rollup of 23 pull requests Successful merges: - #163090 (Run LLDB debuginfo tests on `x86_64-pc-windows-msvc` in CI) - #163806 (even more `tests/crashes` migration for `-Znext-solver`) - #163508 (Document the `rustc_on_unimplemented` attribute.) - #163794 (Use `target_family = "wasm"` instead of `target_arch = "wasm32"`) - #163863 (use the type name instead of `Self` in constructor paths again) - #163864 (Remove CLAUDE.md) - #163877 (Add regression test for duplicated rustdoc search results between std and core) - #163916 (Shrink `PartialRes` and its alignment) - #149753 (On name resolution error in parameter list, suggest possible `const` typo and avoid unnecessary second error) - #152557 (Oneshot `is_ready`) - #157273 (Stabilize `optimize` attribute) - #162000 (peel_transparent_wrappers only works on non-1ZST) - #163343 (`unit` and `[1 x unit]` layouts are incompatible on big-endian targets) - #163348 (perf:cache FFI safety results in improper_ctypes lint) - #163768 (Move more `rustdoc-html` tests in the right location) - #163778 (check is_indirect_first_projection when replacing in RefProp) - #163789 (cg_llvm: Avoid `as_c_char_ptr` in several places) - #163807 (Add `has_reliable_f16b` for Arm) - #163809 (Switch TLS implementation for wasi and bump SDK version to 34) - #163826 (Update books) - #163849 (ci: update to PowerShell 7.6.6) - #163869 (INSTALL.md: use UCRT64 instead of MINGW64 in MSYS2 section) - #163870 (Add if-installed:auto:spellcheck to pre-push script)

Rollup merge of #163789 - Zalathar:as-c-char-ptr, r=hanna-kruppe cg_llvm: Avoid `as_c_char_ptr` in several places As noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. The helper method `as_c_char_ptr` exists to make that extra cast more type-safe, but it's nicer to not need it all. In addition to making call sites a bit simpler, this adjustment also makes it harder to accidentally pass a nul-terminated string to a function expecting a pointer/length string, and vice-versa. There should be no change to compiler output.

rust-timer · 2026-10-08T08:13:52Z

Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (039c207): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.3%, -0.1%]	4
Improvements ✅ (secondary)	-0.2%	[-0.5%, -0.1%]	15
All ❌✅ (primary)	-0.1%	[-0.3%, -0.1%]	4

Max RSS (memory usage)

This perf run didn't have relevant results for this metric.

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Artifact size: 408.59 MiB -> 408.69 MiB (0.02%)

JonathanBrouwer · 2026-10-08T16:22:56Z

This is noise, all PRs in the rollup have the same results

cg_llvm: Avoid some explicit casts to `*const c_char` - Follow-up to rust-lang#163789 --- This is another application of the general principle noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. For the changes in the main commit, a pointer/length string was being passed with `*const c_char` as the pointer type. This PR changes the Rust-side declaration to take `*const c_uchar` instead. Changing the declared type avoids the need for explicit casts, making it easier to notice any accidental type errors. --- A second commit also removes some pointer casts that were completely unnecessary. There should be no change to compiler output.

Rollup merge of #164017 - Zalathar:char-ptr-cast, r=mati865 cg_llvm: Avoid some explicit casts to `*const c_char` - Follow-up to #163789 --- This is another application of the general principle noted in `rustc_codegen_llvm::ffi`: > Normally it's a good idea for Rust-side bindings to match the corresponding C-side function declarations as closely as possible. But when passing `&str` or `&[u8]` data as a pointer/length pair, it's more convenient to declare the Rust-side pointer as `*const c_uchar` instead of `*const c_char`. Both pointer types have the same ABI, and using `*const c_uchar` avoids the need for an extra cast from `*const u8` on the Rust side. For the changes in the main commit, a pointer/length string was being passed with `*const c_char` as the pointer type. This PR changes the Rust-side declaration to take `*const c_uchar` instead. Changing the declared type avoids the need for explicit casts, making it easier to notice any accidental type errors. --- A second commit also removes some pointer casts that were completely unnecessary. There should be no change to compiler output.

…uppe cg_llvm: Avoid all remaining uses of `as_c_char_ptr` Follow-up to: - rust-lang#163789 - rust-lang#164017 --- As explained in the previous PRs (and in the comments for `PTR_LEN_STR`), we can avoid the need for these casts by declaring the relevant FFI bindings to take `*const c_uchar`, which has the same ABI as `*const c_char`. This is more convenient at the call site, and makes it harder to mix up pointer/length strings and nul-terminated strings. There should be no change to compiler output.

Rollup merge of #164071 - Zalathar:as-c-char-ptr, r=hanna-kruppe cg_llvm: Avoid all remaining uses of `as_c_char_ptr` Follow-up to: - #163789 - #164017 --- As explained in the previous PRs (and in the comments for `PTR_LEN_STR`), we can avoid the need for these casts by declaring the relevant FFI bindings to take `*const c_uchar`, which has the same ABI as `*const c_char`. This is more convenient at the call site, and makes it harder to mix up pointer/length strings and nul-terminated strings. There should be no change to compiler output.

…uwer Rollup of 23 pull requests Successful merges: - rust-lang/rust#163090 (Run LLDB debuginfo tests on `x86_64-pc-windows-msvc` in CI) - rust-lang/rust#163806 (even more `tests/crashes` migration for `-Znext-solver`) - rust-lang/rust#163508 (Document the `rustc_on_unimplemented` attribute.) - rust-lang/rust#163794 (Use `target_family = "wasm"` instead of `target_arch = "wasm32"`) - rust-lang/rust#163863 (use the type name instead of `Self` in constructor paths again) - rust-lang/rust#163864 (Remove CLAUDE.md) - rust-lang/rust#163877 (Add regression test for duplicated rustdoc search results between std and core) - rust-lang/rust#163916 (Shrink `PartialRes` and its alignment) - rust-lang/rust#149753 (On name resolution error in parameter list, suggest possible `const` typo and avoid unnecessary second error) - rust-lang/rust#152557 (Oneshot `is_ready`) - rust-lang/rust#157273 (Stabilize `optimize` attribute) - rust-lang/rust#162000 (peel_transparent_wrappers only works on non-1ZST) - rust-lang/rust#163343 (`unit` and `[1 x unit]` layouts are incompatible on big-endian targets) - rust-lang/rust#163348 (perf:cache FFI safety results in improper_ctypes lint) - rust-lang/rust#163768 (Move more `rustdoc-html` tests in the right location) - rust-lang/rust#163778 (check is_indirect_first_projection when replacing in RefProp) - rust-lang/rust#163789 (cg_llvm: Avoid `as_c_char_ptr` in several places) - rust-lang/rust#163807 (Add `has_reliable_f16b` for Arm) - rust-lang/rust#163809 (Switch TLS implementation for wasi and bump SDK version to 34) - rust-lang/rust#163826 (Update books) - rust-lang/rust#163849 (ci: update to PowerShell 7.6.6) - rust-lang/rust#163869 (INSTALL.md: use UCRT64 instead of MINGW64 in MSYS2 section) - rust-lang/rust#163870 (Add if-installed:auto:spellcheck to pre-push script)

Zalathar added 3 commits October 5, 2026 18:16

Avoid as_c_char_ptr in debuginfo

66c7ec6

Avoid as_c_char_ptr in declare.rs

891c24d

Avoid as_c_char_ptr in write.rs

ae54544

rustbot assigned davidtwco Oct 5, 2026

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Rollup of 6 pull requests #163873

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Auto merge of #163789 - Zalathar:as-c-char-ptr, r=<try>

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cg_llvm: Avoid `as_c_char_ptr` in several places try-job: test-various

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Rollup of 24 pull requests #163934

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Toolchain upgrade to nightly-2026-10-09 flux-rs/flux#1811

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cg_llvm: Avoid some explicit casts to *const c_char #164017

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cg_llvm: Avoid `as_c_char_ptr` in several places - #163789

cg_llvm: Avoid `as_c_char_ptr` in several places#163789
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