RE: [PHP-DEV] [Help] Reason on when to declare and protect ZEND_API function

> On Thu, Jan 20, 2022 at 1:56 AM Su, Tao <tao.su@intel.com> wrote: > > > > Hello internals, > > > > I am trying to read Zend header files to understand its functional interfaces, > > but have got confusion and anybody knows why zend_startup_system_id() > and zend_finalize_system_id() > > do not have to be protected by BEGIN_EXTERN_C()/END_EXTERN_C() > enclosure, > > but zend_add_system_entropy() has to. > > > > Is the following code intentional for any reason? > > And also, these two functions do not have ZEND_API attribute. Thanks. > > > > Zend/zend_system_id.h > > BEGIN_EXTERN_C() > > /* True global; Write-only during MINIT/startup */ > > extern ZEND_API char zend_system_id[32]; > > > > ZEND_API ZEND_RESULT_CODE zend_add_system_entropy(const char > *module_name, const char *hook_name, const void *data, size_t size); > > END_EXTERN_C() > > > > void zend_startup_system_id(void); > > void zend_finalize_system_id(void); > > > > > > ======================================= > > Tony Su (Su, Tao) > > make a 'lazy' programmer diligently with efficiency > > > > I haven't looked at the details of these specific functions recently, > but in general functions which are marked ZEND_API are capable of > being called from extensions and modules. These same ZEND_API > functions need to be in extern "C" sections for that > to happen if > the extension or module is using C++. > > I would guess that zend_startup_system_id and > zend_finalize_system_id do not need to be used outside of the > engine > but needed to have a forward declaration for code organization > reasons. Thanks Levi for the clarification. Things become clearer. Here are some following questions 1) when you say 'outside of the engine', what is the boundary of outside/inside? My understanding is that all code under Zend/ folder is considered as inside the Zend engine; Other components outside that folder should be considered as consumer/user of Zend. Is this correct? Pls fix me if I mistook something. Functions marked with ZEND_API in header files under Zend/ folder should be thought as the interface for outside users. Technically, these functions should be marked with extern "C" to support C++ extension/module. Is this correct? Pls fix me if I mistook something. 2) a quick search shows that main/main.c calls zend_startup_system_id() If main/main.c is a Zend user, logically, zend_startup_system_id() should be declared with ZEND_API and extern "C"? /* extract from main/main.c::php_module_startup() */ /* Begin to fingerprint the process state */ zend_startup_system_id(); 3) I found another Zend/zend_gdb.h header file where three functions are marked with ZEND_API but are not enclosed by extern "C". /* Zend/zend_gdb.h */ ZEND_API bool zend_gdb_register_code(const void *object, size_t size); ZEND_API void zend_gdb_unregister_all(void); ZEND_API bool zend_gdb_present(void); 4) In Zend/zend.gdb.c source file, I saw a function __jit_debug_register_code() marked with ZEND_API, but not declared in header file? Logically and programmatically, I got confused and could not grasp ZEND_API usage style. /* Zend/zend_gdb.c */ ZEND_API zend_never_inline void __jit_debug_register_code(void) { __asm__ __volatile__(""); } -- Tao Su