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Jan 28, 2025
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Update comments and sort target_arch in c_char_definition #136173

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16 changes: 9 additions & 7 deletions library/core/src/ffi/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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.):
Expand All @@ -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"),
Expand All @@ -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",
)
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