[libc++][AIX] Fixup problems with ABI list checking

[daltenty]

There are some problems with our ABI list checking exposed by recent compiler/cmake upgrades.

• For symcheck, there are typos in how XCOFF magic are defined, we intended the second two digits to be a hex value, but our syntax doesn't say that. Thus this will never match a valid XCOFF file.
• AIX triples can have version numbers. Those need to be discarded when looking for an libc++ ABI list, like we do for other targets.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: David Tenty (daltenty)

Changes

There are some typos here in how XCOFF magic are defined, we intended the second two digits to be a hex value, but our syntax doesn't say that. Thus this will never match.

---

Full diff: https://github.com/llvm/llvm-project/pull/155643.diff

1 Files Affected:

• (modified) libcxx/utils/libcxx/sym_check/util.py (+1-1)

diff --git a/libcxx/utils/libcxx/sym_check/util.py b/libcxx/utils/libcxx/sym_check/util.py
index fc7ba4244ab5a..dbc886f29ddea 100644
--- a/libcxx/utils/libcxx/sym_check/util.py
+++ b/libcxx/utils/libcxx/sym_check/util.py
@@ -95,7 +95,7 @@ def is_xcoff_or_big_ar(filename):
     with open(filename, "rb") as f:
         magic_bytes = f.read(7)
     return (
-        magic_bytes[:4] in [b"\x01DF", b"\x01F7"]  # XCOFF32  # XCOFF64
+        magic_bytes[:2] in [b"\x01\xDF", b"\x01\xF7"]  # XCOFF32  # XCOFF64
         or magic_bytes == b"<bigaf>"
     )
 

[jakeegan]

LGTM

[hubert-reinterpretcast]

LGTM with minor nit.

[amy-kwan]

This should ideally be in LLVM 21.x, as well.

/cherry-pick b8456e2

[llvmbot]

/pull-request #156502