[libc] add LLVM_LIBC_CAST macro.
#127319
[libc] add LLVM_LIBC_CAST macro.
#127319
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@llvm/pr-subscribers-libc Author: None (c8ef) Changesrelated: #127238 This patch adds a macro called Full diff: https://github.com/llvm/llvm-project/pull/127319.diff 1 Files Affected:
diff --git a/libc/include/__llvm-libc-common.h b/libc/include/__llvm-libc-common.h
index a0fa506c01ab8..83682e0a440d8 100644
--- a/libc/include/__llvm-libc-common.h
+++ b/libc/include/__llvm-libc-common.h
@@ -47,6 +47,9 @@
#define __NOEXCEPT throw()
#endif
+#undef LLVM_LIBC_CAST
+#define LLVM_LIBC_CAST(cast, type, value) (cast<type>(value))
+
#else // not __cplusplus
#undef __BEGIN_C_DECLS
@@ -85,6 +88,9 @@
#undef _Returns_twice
#define _Returns_twice __attribute__((returns_twice))
+#undef LLVM_LIBC_CAST
+#define LLVM_LIBC_CAST(cast, type, value) ((type)(value))
+
#endif // __cplusplus
#endif // LLVM_LIBC_COMMON_H
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libc/include/__llvm-libc-common.h
Outdated
| @@ -47,6 +47,9 @@ | |||
| #define __NOEXCEPT throw() | |||
| #endif | |||
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|||
| #undef LLVM_LIBC_CAST | |||
| #define LLVM_LIBC_CAST(cast, type, value) (cast<type>(value)) | |||
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This merits a comment about its intended uses.
No macro should be defined in this file unless it's in the implementation namespace.
Sticking to the __ prefix seems like the best convention, with the exception of the C11 keywords that are in the _[A-Z] part of the implementation namespace.
| #define htole16(x) ((uint16_t)(x)) | ||
| #define htole32(x) ((uint32_t)(x)) | ||
| #define htole64(x) ((uint64_t)(x)) | ||
| #define htole16(x) __LLVM_LIBC_CAST(reinterpret_cast, uint16_t, x) |
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Could we just make the reinterpret cast implicit? Unsure if we'd ever need it.
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The bionic implementation omits it, while the glibc, musl, and freebsd implementations enforce it. Unsure which is more suitable.
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The CI error seems unrelated. |
| #define htole16(x) ((uint16_t)(x)) | ||
| #define htole32(x) ((uint32_t)(x)) | ||
| #define htole64(x) ((uint64_t)(x)) | ||
| #define htole16(x) __LLVM_LIBC_CAST(reinterpret_cast, uint16_t, x) |
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I don't think this should be a reinterpret_cast. Since these types should be compatible I think this should be a static_cast.
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Thank you for your review! I will merge this PR now and address any further comments in future patches. |
related: #127238
This patch adds a macro called
LLVM_LIBC_CAST, similar to__BIONIC_CAST, for type conversion inendian.h.