[all-commits] [llvm/llvm-project] 5a530a: [libc] Reimplement IN6_IS_ADDR_* macros using stat...

[Pavel Labath via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5a530a22fae4aaa41da79779cd56db57f8de55f8
      https://github.com/llvm/llvm-project/commit/5a530a22fae4aaa41da79779cd56db57f8de55f8
  Author: Pavel Labath <pavel at labath.sk>
  Date:   2026-07-16 (Thu, 16 Jul 2026)

  Changed paths:
    M libc/include/llvm-libc-macros/netinet-in-macros.h
    M libc/test/include/netinet_in_test.cpp

  Log Message:
  -----------
  [libc] Reimplement IN6_IS_ADDR_* macros using statement expressions (#209772)

This patch fixes three issues with the previous implementation:
- the macro argument was being evaluated more than once
- casting to other types (uint32_t in particular) was an aliasing
violation
- it was casting to non-const pointers, resulting in compiler errors in
cases where the user passes a const ptr.

A statement expression fixes the first issue by using a temporary
variable. The second issue is fixed by using the appropriate members of
struct in6_addr. The last issue is fixed by dropping the cast
completely. This requires the user to pass a correctly types pointer (as
POSIX requires). Implementations keep it for compatibility with old code
passing void * and similar, but a quick survey shows that most modern
code passes the correct types. If this turns out to be an issue, we can
easily add the cast (to a const type) back.

Implementation notes:
- IN6_IS_ADDR_MULTICAST doesn't use the statement expression because the
argument is evaluated only once
- I use private helper macros (__IN6_IS_ADDR_UNSPECIFIED and
__IN6_IS_ADDR_LOOPBACK) so IN6_IS_ADDR_V4COMPAT does not nest statement
expressions
- I considered using private entrypoints (like we do with cpuset macros)
instead of statement expressions, but decided against it because these
macros are simpler and would thus result in a higher
boilerplate-to-useful-code ratio (particularly given our restriction on
calling other entrypoints)

Assisted by Gemini.



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