memcpy() usage without #include <string.h> in pwdmodule.c

Bug report

Bug description:

For a non-gcc/clang compiler, _Py_TYPEOF is not defined.

Lines 548 to 551 in c08a302

    
           // The macro is only defined if GCC or clang compiler is used. 
        
           #if defined(__GNUC__) || defined(__clang__) 
        
           #  define _Py_TYPEOF(expr) __typeof__(expr) 
        
           #endif

Which leads to Py_CLEAR() fallback to an implementation with memcpy() call.

cpython/Include/object.h

Lines 1016 to 1027 in c08a302

    
           #else 
        
           #define Py_CLEAR(op) \ 
        
               do { \ 
        
                   PyObject **_tmp_op_ptr = _Py_CAST(PyObject**, &(op)); \ 
        
                   PyObject *_tmp_old_op = (*_tmp_op_ptr); \ 
        
                   if (_tmp_old_op != NULL) { \ 
        
                       PyObject *_null_ptr = _Py_NULL; \ 
        
                       memcpy(_tmp_op_ptr, &_null_ptr, sizeof(PyObject*)); \ 
        
                       Py_DECREF(_tmp_old_op); \ 
        
                   } \ 
        
               } while (0) 
        
           #endif

Py_CLEAR() is used in ./Modules/pwdmodule.c

cpython/Modules/pwdmodule.c

Lines 355 to 358 in c08a302

    
           static int pwdmodule_clear(PyObject *m) { 
        
               Py_CLEAR(get_pwd_state(m)->StructPwdType); 
        
               return 0; 
        
           }

without including string.h

cpython/Modules/pwdmodule.c

Lines 12 to 16 in c08a302

    
           #include <errno.h>                // ERANGE 
        
           #include <pwd.h>                  // getpwuid() 
        
           #include <unistd.h>               // sysconf()

For a non-gcc/clang compiler, this may fail due to missing memcpy() declaration.

./Include/object.h:1017: #define Py_CLEAR(op)     do {         PyObject **_tmp_op_ptr = _Py_CAST(PyObject**, &(op));         PyObject *_tmp_old_op = (*_tmp_op_ptr);         if (_tmp_old_op != NULL) {             PyObject *_null_ptr = _Py_NULL;             memcpy(_tmp_op_ptr, &_null_ptr, sizeof(PyObject*));             Py_DECREF(_tmp_old_op);         }     } while (0)
                                                                                                                                                                                                                                                                ^ implicit declaration of a function
./Modules/pwdmodule.c:356:     Py_CLEAR(get_pwd_state(m)->StructPwdType);
                               ^ in expansion of macro

On a side note, typeof is widely implemented among alternative C compilers like TinyCC and cproc, kefir, chibicc, and is standardized in C23. It could be beneficial to enable typeof usage through configure option or probing, instead of hard-coded off on non-gcc/clang compilers.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

pythongh-121617: Include <string.h> for Py_CLEAR() macro (python#144666)

gh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (#157067)

pythongh-121617: Fix Py_CLEAR() memcpy in C++: replace NULL with _Py_…

pythongh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (p…

[3.14] gh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (#…

[3.13] gh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (#…

gh-121617: Fix Py_CLEAR() memcpy in C++: replace NULL with _Py_NULL (#…

Merge branch 'main' into tachyon-native-callable

pythongh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (p…

pythongh-121617: Fix Py_CLEAR() memcpy in C++: replace NULL with _Py_…

pythongh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (p…

pythongh-121617: Fix Py_CLEAR() memcpy in C++: replace NULL with _Py_…

[3.15] gh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (G…

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`memcpy()` usage without `#include <string.h>` in `pwdmodule.c` #121617

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	// The macro is only defined if GCC or clang compiler is used.
	#if defined(__GNUC__) \|\| defined(__clang__)
	# define _Py_TYPEOF(expr) __typeof__(expr)
	#endif

	#else
	#define Py_CLEAR(op) \
	do { \
	PyObject _tmp_op_ptr = _Py_CAST(PyObject, &(op)); \
	PyObject _tmp_old_op = (_tmp_op_ptr); \
	if (_tmp_old_op != NULL) { \
	PyObject *_null_ptr = _Py_NULL; \
	memcpy(_tmp_op_ptr, &_null_ptr, sizeof(PyObject*)); \
	Py_DECREF(_tmp_old_op); \
	} \
	} while (0)
	#endif

	static int pwdmodule_clear(PyObject *m) {
	Py_CLEAR(get_pwd_state(m)->StructPwdType);
	return 0;
	}


	#include <errno.h> // ERANGE
	#include <pwd.h> // getpwuid()
	#include <unistd.h> // sysconf()

memcpy() usage without #include <string.h> in pwdmodule.c #121617

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`memcpy()` usage without `#include <string.h>` in `pwdmodule.c` #121617