Read PHP 8.6 thread-safe EG() and CG() through the exported offsets

PHP 8.6's thread-safe headers compute the offset of the executor and
compiler globals from sizeof(zend_executor_globals) and
sizeof(zend_compiler_globals), and EG()/CG() compile that constant into
every use. The module API number does not guard those sizes: 8.6.0RC4
appended `delayed_oom` to the executor globals (php-src 3584a98bda0, a
security fix), so an extension built against RC3's headers read and wrote
every EG() field 32 bytes off and crashed on startup.

Redefine EG() and CG() to go through executor_globals_offset and
compiler_globals_offset, which the engine exports, as the headers do up to
8.5. The redefinition comes before the rest of the engine headers, so
their inline functions use it too. Only the version-specific objects
change; the shared core compiles to the same code as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0135ph8YpHvnbDwd4G6rozNY

Author: ondrejmirtes

turbo-ext/src/support.h

@@ -29,6 +29,27 @@
  * every gcc/libc target supports — gcc then warns the attribute is ignored */
 #pragma GCC diagnostic ignored "-Wattributes"
 
+extern "C" {
+#include "php_version.h"
+#include "zend_globals_macros.h"
+}
+
+/* PHP 8.6's thread-safe EG() and CG() reach the globals at an offset the
+ * headers compute from sizeof(zend_executor_globals) and
+ * sizeof(zend_compiler_globals) — a constant compiled into every use, which
+ * the module API number does not guard: 8.6.0RC4 appended a field to the
+ * executor globals, and an extension built against RC3's headers read and
+ * wrote every EG() field 32 bytes off. Read through the offsets the engine
+ * exports instead, as the headers do up to 8.5, so a field appended by a
+ * later release moves nothing. Redefined before the rest of the headers, so
+ * their inline functions get it too. */
+#if defined(ZTS) && PHP_VERSION_ID >= 80600
+#undef EG
+#undef CG
+#define EG(v) ZEND_TSRMG_FAST(executor_globals_offset, zend_executor_globals *, v)
+#define CG(v) ZEND_TSRMG_FAST(compiler_globals_offset, zend_compiler_globals *, v)
+#endif
+
 extern "C" {
 #include "php.h"
 #include "zend_exceptions.h"