[php-src] master: Zend: compile time assert on Bucket size (#23079)

Author: Sjoerd Langkemper (Sjord)
Committer: GitHub (web-flow)
Pusher: arnaud-lb
Date: 2026-08-10T10:04:23+02:00

Commit: https://github.com/php/php-src/commit/5206ff33ca21be3bcbe5e402fcb856978ff457df
Raw diff: https://github.com/php/php-src/commit/5206ff33ca21be3bcbe5e402fcb856978ff457df.diff

Zend: compile time assert on Bucket size (#23079)

In zend_compile.c, flags are stored in the lower bits of the Bucket
address. If Bucket is aligned to 8 bytes, the lower three bits are
always zero and this gives no problems. If the Bucket is not aligned,
this results in non-obvious errors because the memory address and the
flags overlap. This is difficult to debug when it happens, so add this
assertion to make it more obvious what is wrong.

The flags are ZEND_BIND_REF, ZEND_BIND_IMPLICIT, ZEND_BIND_EXPLICIT.

Related to GH-19079

Changed paths:
  M  Zend/zend_compile.c


Diff:

diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index a2f126fb101d..882b1bf990bf 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -5916,6 +5916,8 @@ static void zend_compile_static_var_common(zend_string *var_name, zval *value, u
 	opline = zend_emit_op(NULL, ZEND_BIND_STATIC, NULL, NULL);
 	opline->op1_type = IS_CV;
 	opline->op1.var = lookup_cv(var_name);
+
+	ZEND_STATIC_ASSERT(sizeof(Bucket) % 8 == 0, "Bucket size not compatible with storing flags in lower three bits");
 	opline->extended_value = (uint32_t)((char*)value - (char*)CG(active_op_array)->static_variables->arData) | mode;
 }
 /* }}} */