PHP內核中重要的兩個全局變量

在閱讀PHP源碼的時候，會遇到很多諸如：CG()，EG() 這樣的宏，如果不了解這些宏的意義，會給理解源碼造成很大困難。

Zend引擎中有兩個重要的全局變量結構體，就是Zend引擎關閉之前都會存在的變量：

typedef struct _zend_compiler_globals zend_compiler_globals;
typedef struct _zend_executor_globals zend_executor_globals;

/* Compiler */
#ifdef ZTS
# define CG(v) TSRMG(compiler_globals_id, zend_compiler_globals *, v)
int zendparse(void *compiler_globals);
#else
# define CG(v) (compiler_globals.v)
extern ZEND_API struct _zend_compiler_globals compiler_globals;
int zendparse(void);
#endif

/* Executor */
#ifdef ZTS
# define EG(v) TSRMG(executor_globals_id, zend_executor_globals *, v)
#else
# define EG(v) (executor_globals.v)
extern ZEND_API zend_executor_globals executor_globals;
#endif

CG 的含義就是 compiler_globals ，Zend編譯器相關的全局變量； 

EG 的含義就是 executor_globals，Zend執行器相關的全局變量；

這兩個結構都包含了很多元素，對理解PHP內核有很重要的意義：

struct _zend_compiler_globals {
 zend_stack bp_stack;
 zend_stack switch_cond_stack;
 zend_stack foreach_copy_stack;
 zend_stack object_stack;
 zend_stack declare_stack;

 zend_class_entry *active_class_entry;

 /* variables for list() compilation */
 zend_llist list_llist;
 zend_llist dimension_llist;
 zend_stack list_stack;

 zend_stack function_call_stack;

 char *compiled_filename;

 int zend_lineno;
 int comment_start_line;
 char *heredoc;
 int heredoc_len;

 zend_op_array *active_op_array;

 HashTable *function_table; /* function symbol table */
 HashTable *class_table;  /* class table */

 HashTable filenames_table;

 HashTable *auto_globals;

 zend_bool in_compilation;
 zend_bool short_tags;
 zend_bool asp_tags;
 zend_bool allow_call_time_pass_reference;

 zend_declarables declarables;

 /* For extensions support */
 zend_bool extended_info; /* generate extension information for debugger/profiler */
 zend_bool handle_op_arrays; /* run op_arrays through op_array handlers */

 zend_bool unclean_shutdown;

 zend_bool ini_parser_unbuffered_errors;

 zend_llist open_files;

 long catch_begin;

 struct _zend_ini_parser_param *ini_parser_param;

 int interactive;

 zend_uint start_lineno;
 zend_bool increment_lineno;

 znode implementing_class;

 zend_uint access_type;

 char *doc_comment;
 zend_uint doc_comment_len;

#ifdef ZEND_MULTIBYTE
 zend_encoding **script_encoding_list;
 int script_encoding_list_size;
 zend_bool detect_unicode;

 zend_encoding *internal_encoding;

 /* multibyte utility functions */
 zend_encoding_detector encoding_detector;
 zend_encoding_converter encoding_converter;
 zend_encoding_oddlen encoding_oddlen;
#endif /* ZEND_MULTIBYTE */

#ifdef ZTS
 HashTable **static_members;
 int last_static_member;
#endif
};

struct _zend_executor_globals {
 zval **return_value_ptr_ptr;

 zval uninitialized_zval;
 zval *uninitialized_zval_ptr;

 zval error_zval;
 zval *error_zval_ptr;

 zend_function_state *function_state_ptr;
 zend_ptr_stack arg_types_stack;

 /* symbol table cache */
 HashTable *symtable_cache[SYMTABLE_CACHE_SIZE];
 HashTable **symtable_cache_limit;
 HashTable **symtable_cache_ptr;

 zend_op **opline_ptr;

 HashTable *active_symbol_table;
 HashTable symbol_table;  /* main symbol table */

 HashTable included_files; /* files already included */

 jmp_buf *bailout;

 int error_reporting;
 int orig_error_reporting;
 int exit_status;

 zend_op_array *active_op_array;

 HashTable *function_table; /* function symbol table */
 HashTable *class_table;  /* class table */
 HashTable *zend_constants; /* constants table */

 zend_class_entry *scope;

 zval *This;

 long precision;

 int ticks_count;

 zend_bool in_execution;
 HashTable *in_autoload;
 zend_function *autoload_func;
 zend_bool full_tables_cleanup;
 zend_bool ze1_compatibility_mode;

 /* for extended information support */
 zend_bool no_extensions;

#ifdef ZEND_WIN32
 zend_bool timed_out;
#endif

 HashTable regular_list;
 HashTable persistent_list;

 zend_ptr_stack argument_stack;

 int user_error_handler_error_reporting;
 zval *user_error_handler;
 zval *user_exception_handler;
 zend_stack user_error_handlers_error_reporting;
 zend_ptr_stack user_error_handlers;
 zend_ptr_stack user_exception_handlers;

 /* timeout support */
 int timeout_seconds;

 int lambda_count;

 HashTable *ini_directives;
 HashTable *modified_ini_directives;

 zend_objects_store objects_store;
 zval *exception;
 zend_op *opline_before_exception;

 struct _zend_execute_data *current_execute_data;

 struct _zend_module_entry *current_module;

 zend_property_info std_property_info;

 zend_bool active;

 void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};

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