全局变量EG、CG

EG

在PHP的源码中，大量充斥着EG、PG这种宏定义。在zend_globals_macros.h中，可以看到EG的定义：

#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

ZTS表示线程安全。比如使用EG(function_table)的话，那么就会使用executor_globals.function_table。而zend_executor_globals在该文件中，也可以看到：

typedef struct _zend_executor_globals zend_executor_globals;

可以看到zend_executor_globals只是_zend_executor_globals的一个别名。而_zend_executor_globals则是在zend_globals.h中被定义：

struct _zend_executor_globals {
zval **return_value_ptr_ptr;

zval uninitialized_zval;
zval *uninitialized_zval_ptr;

zval error_zval;
zval *error_zval_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;
zend_class_entry *called_scope; /* Scope of the calling class */

zval *This;

long precision;

int ticks_count;

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

/* for extended information support */
zend_bool no_extensions;

#ifdef ZEND_WIN32
zend_bool timed_out;
OSVERSIONINFOEX windows_version_info;
#endif

HashTable regular_list;
HashTable persistent_list;

zend_vm_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;

zend_error_handling_t  error_handling;
zend_class_entry      *exception_class;

/* timeout support */
int timeout_seconds;

int lambda_count;

HashTable *ini_directives;
HashTable *modified_ini_directives;
zend_ini_entry *error_reporting_ini_entry;

zend_objects_store objects_store;
zval *exception, *prev_exception;
zend_op *opline_before_exception;
zend_op exception_op[3];

struct _zend_execute_data *current_execute_data;

struct _zend_module_entry *current_module;

zend_property_info std_property_info;

zend_bool active;

zend_op *start_op;

void *saved_fpu_cw_ptr;
#if XPFPA_HAVE_CW
XPFPA_CW_DATATYPE saved_fpu_cw;
#endif

void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};

所以可以得知，EG宏的主要功能是查找全局变量_zend_executor_globals中的成员。比如EG(function_table)便是查找_zend_executor_globals中的function_table成员。

CG

类似上面的EG。这里的CG也不难得出是引用某个全局的变量。在php源码中，通常在在某个宏是以G结束的，则是使用某个全局的变量。

#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

_zend_compiler_globals也是在zend_globals.h中定义：

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;

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 parse_error;
zend_bool in_compilation;
zend_bool short_tags;
zend_bool asp_tags;

zend_declarables declarables;

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;

zend_uint compiler_options; /* set of ZEND_COMPILE_* constants */

zval      *current_namespace;
HashTable *current_import;
zend_bool  in_namespace;
zend_bool  has_bracketed_namespaces;

zend_compiler_context context;
zend_stack context_stack;

/* interned strings */
char *interned_strings_start;
char *interned_strings_end;
char *interned_strings_top;
char *interned_strings_snapshot_top;

HashTable interned_strings;

const zend_encoding **script_encoding_list;
size_t script_encoding_list_size;
zend_bool multibyte;
zend_bool detect_unicode;
zend_bool encoding_declared;

#ifdef ZTS
zval ***static_members_table;
int last_static_member;

#endif
};