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Description

Fixes #10497 - Allows direct modification of object properties stored in constants.

Problem

Previously, this code would fail with a fatal error:

const a = new stdClass;
a->b = 42;  // Fatal error: Cannot use temporary expression in write context

Solution

Modified the compiler to properly handle ZEND_AST_CONST in variable compilation contexts:

Constants now emit IS_VAR instead of IS_TMP_VAR when used in write contexts
This allows property assignment opcodes to work correctly with constant objects

Tests:

  • Added Zend/tests/gh10497.phpt - comprehensive test for the fix
  • Updated Zend/tests/gh12102_3.phpt - reflects improved constant handling

Behavior

Now supports all property operations on constant objects:

const obj = new stdClass;
obj->prop = 'value';
obj->prop = 'new value';
obj->another = 'test';
obj->counter = 0;
obj->counter++;
obj->num = 10;
obj->num += 5;
unset(obj->prop);
obj->nested = new stdClass;
obj->nested->value = 123;

The constant reference remains immutable, but the object itself is mutable as expected.

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@iluuu1994 iluuu1994 left a comment

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Thanks @khaledalam! Looks reasonable overall.

*result = *zend_ast_get_znode(ast);
return NULL;
case ZEND_AST_CONST:
return zend_compile_const_inner(result, ast, false);
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You should pass type directly and only produce IS_VAR when in write-context (BP_VAR_W or BP_VAR_RW).

/* }}} */

static void zend_compile_const(znode *result, const zend_ast *ast) /* {{{ */
static zend_op *zend_compile_const_inner(znode *result, const zend_ast *ast, bool use_tmp) /* {{{ */
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zend_compile_const() is only used from one other place, no need for this BC layer. You can just pass BP_VAR_R from zend_compile_expr_inner().

resolved_name, true);
}
opline->extended_value = zend_alloc_cache_slot();
return opline;
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This return value should be unneded. It's only needed for specific opcodes, e.g. to add some extended_value flag. Just return NULL from zend_compile_var_inner().

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Cannot directly modify an object stored in a constant

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