PHP 8.5.0: preserve_none check fails on macOS (undefined symbol `fun` as macOS uses `_fun`)

[cho-m]

Description

While preparing PHP 8.5.0 release in Homebrew (Homebrew/homebrew-core#255299), I noticed that the new TAILCALL VM feature wasn't getting enabled on macOS.

From config.log, the error is

configure:81621: checking for preserve_none calling convention
configure:81715: clang -o conftest -g -O2 -ffp-contract=off -fvisibility=hidden -DNDEBUG  -D_GNU_SOURCE  -Wl,-rpath,/opt/homebrew/Cellar/openssl@3/3.6.0/lib -L/opt/homebrew/Cellar/openssl@3/3.6.0/lib -Wl,-rpath,/opt/homebrew/Cellar/pcre2/10.47/lib -L/opt/homebrew/Cellar/pcre2/10.47/lib -Wl,-rpath,/opt/homebrew/opt/sqlite/lib -L/opt/homebrew/opt/sqlite/lib -Wl,-rpath,/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/usr/lib -L/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/usr/lib -Wl,-rpath,/opt/homebrew/Cellar/curl/8.17.0/lib -L/opt/homebrew/Cellar/curl/8.17.0/lib -Wl,-rpath,/opt/homebrew/Cellar/gd/2.3.3_6/lib -L/opt/homebrew/Cellar/gd/2.3.3_6/lib -Wl,-rpath,/opt/homebrew/opt/gettext/lib -L/opt/homebrew/opt/gettext/lib -Wl,-rpath,/opt/homebrew/opt/gmp/lib -L/opt/homebrew/opt/gmp/lib -Wl,-rpath,/opt/homebrew/opt/openldap/lib -L/opt/homebrew/opt/openldap/lib -Wl,-rpath,/opt/homebrew/Cellar/oniguruma/6.9.10/lib -L/opt/homebrew/Cellar/oniguruma/6.9.10/lib -Wl,-rpath,/opt/homebrew/Cellar/unixodbc/2.3.14/lib -L/opt/homebrew/Cellar/unixodbc/2.3.14/lib -Wl,-rpath,/opt/homebrew/opt/freetds/lib -L/opt/homebrew/opt/freetds/lib -Wl,-rpath,/opt/homebrew/opt/libpq/lib -L/opt/homebrew/opt/libpq/lib -Wl,-rpath,/opt/homebrew/Cellar/net-snmp/5.9.4/lib -L/opt/homebrew/Cellar/net-snmp/5.9.4/lib -Wl,-rpath,/opt/homebrew/opt/openssl@3/lib -L/opt/homebrew/opt/openssl@3/lib -Wl,-rpath,/opt/homebrew/Cellar/libsodium/1.0.20/lib -L/opt/homebrew/Cellar/libsodium/1.0.20/lib -Wl,-rpath,/opt/homebrew/Cellar/argon2/20190702_1/lib -L/opt/homebrew/Cellar/argon2/20190702_1/lib -Wl,-rpath,/opt/homebrew/opt/tidy-html5/lib -L/opt/homebrew/opt/tidy-html5/lib -Wl,-rpath,/opt/homebrew/Cellar/libzip/1.11.4/lib -L/opt/homebrew/Cellar/libzip/1.11.4/lib conftest.c  >&5
Undefined symbols for architecture arm64:
  "fun", referenced from:
      _test in conftest-4b4b9c.o
      _main in conftest-4b4b9c.o

This can also be reproduced by just trying to manually compile - https://github.com/php/php-src/blob/php-8.5.0/Zend/Zend.m4#L479

The issue is due to macOS symbol being _fun not fun, e.g.

❯ clang -c test.c && nm -gU test.o | grep fun
0000000000000000 T _fun

php-src/Zend/Zend.m4

Line 518 in ca7f556

"bl fun\n"

Also, minor issue but there is a typo (preverve) which I noticed when trying to override the cache variable

php-src/Zend/Zend.m4

Line 477 in 685e996

[php_cv_preverve_none],

PHP Version

PHP 8.5.0 (cli) (built: Nov 18 2025 08:02:20) (NTS)
Copyright (c) The PHP Group
Built by Homebrew
Zend Engine v4.5.0, Copyright (c) Zend Technologies
    with Zend OPcache v8.5.0, Copyright (c), by Zend Technologies

Operating System

macOS 26

[devnexen]

Nice report. The following little changes fix it for me (I know mac intel are no longer a thing but just in case..)

diff --git a/Zend/Zend.m4 b/Zend/Zend.m4
index 1e1853167cf..33009e9909f 100644
--- a/Zend/Zend.m4
+++ b/Zend/Zend.m4
@@ -474,7 +474,7 @@ dnl expectations.
 dnl
 AC_DEFUN([ZEND_CHECK_PRESERVE_NONE], [dnl
   AC_CACHE_CHECK([for preserve_none calling convention],
-   [php_cv_preverve_none],
+   [php_cv_preserve_none],
    [AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <stdio.h>
 #include <stdint.h>
@@ -504,7 +504,11 @@ uintptr_t __attribute__((preserve_none)) test(void) {
                "movq %2, %%r13\n"
                "xorq %3, %%r13\n"
                "xorq %%rax, %%rax\n"
+#if defined(__APPLE__)
+               "call _fun\n"
+#else
                "call fun\n"
+#endif
                : "=a" (ret)
                : "r" (const1), "r" (const2), "r" (key)
                : "r12", "r13"
@@ -515,7 +519,11 @@ uintptr_t __attribute__((preserve_none)) test(void) {
                "eor    x20, %1, %3\n"
                "eor    x21, %2, %3\n"
                "eor    x0, x0, x0\n"
+#if defined(__APPLE__)
+               "bl     _fun\n"
+#else
                "bl     fun\n"
+#endif
                "mov    %0, x0\n"
                : "=r" (ret)
                : "r" (const1), "r" (const2), "r" (key)