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Rollup merge of #136173 - taiki-e:c-char, r=tgross35

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Update comments and sort target_arch in c_char_definition

Follow-up to https://github.com/rust-lang/rust/pull/132975.

- Clang's wrong default on MSP430 has been fixed in https://github.com/llvm/llvm-project/pull/115964, and will be included in LLVM 20, which will be used soon.
- Add a reference on Xtensa's default (from https://github.com/rust-lang/rust/pull/132975#issuecomment-2484645240).
- Fix link for Windows's default.
- Add a link to the discussion on L4Re (https://github.com/rust-lang/rust/pull/132975#issuecomment-2484645240)
- Sort `target_arch`. (now match with `target_arch`s in comments)

r? `@tgross35`
This commit is contained in:
Matthias Krüger 2025-01-28 18:17:30 +01:00 • committed by GitHub
commit 36b5c58ef8
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1 changed files with 9 additions and 7 deletions
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16
library/core/src/ffi/mod.rs
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@ -116,7 +116,6 @@ mod c_char_definition {
// Section 2.1 "Basic Types" in MSP430 Embedded Application Binary
// Interface says "The char type is unsigned by default".
// https://www.ti.com/lit/an/slaa534a/slaa534a.pdf
// Note: this doesn't seem to match Clang's default (https://github.com/rust-lang/rust/issues/129945).
// powerpc/powerpc64:
// - PPC32 SysV: "Table 3-1 Scalar Types" in System V Application Binary Interface PowerPC
// Processor Supplement says ANSI C char is unsigned byte
@ -139,8 +138,10 @@ mod c_char_definition {
// https://github.com/IBM/s390x-abi/releases/tag/v1.6.1
// - z/OS: XL C/C++ Language Reference says: "By default, char behaves like an unsigned char."
// https://www.ibm.com/docs/en/zos/3.1.0?topic=specifiers-character-types
// Xtensa:
// - "The char type is unsigned by default for Xtensa processors."
// xtensa:
// Section 2.17.1 "Data Types and Alignment" of Xtensa LX Microprocessor Overview handbook
// says "`char` type is unsigned by default".
// https://loboris.eu/ESP32/Xtensa_lx%20Overview%20handbook.pdf
//
// On the following operating systems, c_char is signed by default, regardless of architecture.
// Darwin (macOS, iOS, etc.):
@ -150,11 +151,12 @@ mod c_char_definition {
// Windows MSVC C++ Language Reference says "Microsoft-specific: Variables of type char
// are promoted to int as if from type signed char by default, unless the /J compilation
// option is used."
// https://learn.microsoft.com/en-us/cpp/cpp/fundamental-types-cpp?view=msvc-170#character-types)
// L4RE:
// https://learn.microsoft.com/en-us/cpp/cpp/fundamental-types-cpp?view=msvc-170#character-types
// L4Re:
// The kernel builds with -funsigned-char on all targets (but useserspace follows the
// architecture defaults). As we only have a target for userspace apps so there are no
// special cases for L4RE below.
// special cases for L4Re below.
// https://github.com/rust-lang/rust/pull/132975#issuecomment-2484645240
if #[cfg(all(
not(windows),
not(target_vendor = "apple"),
@ -166,8 +168,8 @@ mod c_char_definition {
target_arch = "msp430",
target_arch = "powerpc",
target_arch = "powerpc64",
target_arch = "riscv64",
target_arch = "riscv32",
target_arch = "riscv64",
target_arch = "s390x",
target_arch = "xtensa",
)