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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add support for C99 complex type (_Complex) to the struct module","articleBody":"# Feature or enhancement\n\n### Proposal:\n\nThe struct module has support for ``float`` and ``double`` types, so at least there should be also ``float _Complex`` and ``double _Complex``.  I'll work on a patch.\n\n\u003cdetails\u003e\n\n\u003csummary\u003eInitial version\u003c/summary\u003e\n\n```diff\ndiff --git a/Lib/ctypes/__init__.py b/Lib/ctypes/__init__.py\nindex d2e6a8bfc8..d941036719 100644\n--- a/Lib/ctypes/__init__.py\n+++ b/Lib/ctypes/__init__.py\n@@ -208,6 +208,7 @@ class c_longdouble(_SimpleCData):\n try:\n     class c_double_complex(_SimpleCData):\n         _type_ = \"C\"\n+    _check_size(c_double_complex)\n except AttributeError:\n     pass\n \ndiff --git a/Modules/_struct.c b/Modules/_struct.c\nindex 6a68478dd4..caf4975413 100644\n--- a/Modules/_struct.c\n+++ b/Modules/_struct.c\n@@ -12,6 +12,9 @@\n #include \"pycore_long.h\"          // _PyLong_AsByteArray()\n #include \"pycore_moduleobject.h\"  // _PyModule_GetState()\n \n+#ifdef Py_HAVE_C_COMPLEX\n+#  include \"_complex.h\"           // complex\n+#endif\n #include \u003cstddef.h\u003e               // offsetof()\n \n /*[clinic input]\n@@ -80,6 +83,9 @@ typedef struct { char c; int x; } st_int;\n typedef struct { char c; long x; } st_long;\n typedef struct { char c; float x; } st_float;\n typedef struct { char c; double x; } st_double;\n+#ifdef Py_HAVE_C_COMPLEX\n+typedef struct { char c; double complex x; } st_double_complex;\n+#endif\n typedef struct { char c; void *x; } st_void_p;\n typedef struct { char c; size_t x; } st_size_t;\n typedef struct { char c; _Bool x; } st_bool;\n@@ -89,6 +95,9 @@ typedef struct { char c; _Bool x; } st_bool;\n #define LONG_ALIGN (sizeof(st_long) - sizeof(long))\n #define FLOAT_ALIGN (sizeof(st_float) - sizeof(float))\n #define DOUBLE_ALIGN (sizeof(st_double) - sizeof(double))\n+#ifdef Py_HAVE_C_COMPLEX\n+#define DOUBLE_COMPLEX_ALIGN (sizeof(st_double_complex) - sizeof(double complex))\n+#endif\n #define VOID_P_ALIGN (sizeof(st_void_p) - sizeof(void *))\n #define SIZE_T_ALIGN (sizeof(st_size_t) - sizeof(size_t))\n #define BOOL_ALIGN (sizeof(st_bool) - sizeof(_Bool))\n@@ -518,6 +527,17 @@ nu_double(_structmodulestate *state, const char *p, const formatdef *f)\n     return PyFloat_FromDouble(x);\n }\n \n+#ifdef Py_HAVE_C_COMPLEX\n+static PyObject *\n+nu_double_complex(_structmodulestate *state, const char *p, const formatdef *f)\n+{\n+    double complex x;\n+\n+    memcpy(\u0026x, p, sizeof(x));\n+    return PyComplex_FromDoubles(creal(x), cimag(x));\n+}\n+#endif\n+\n static PyObject *\n nu_void_p(_structmodulestate *state, const char *p, const formatdef *f)\n {\n@@ -791,6 +811,24 @@ np_double(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)\n     return 0;\n }\n \n+#ifdef Py_HAVE_C_COMPLEX\n+static int\n+np_double_complex(_structmodulestate *state, char *p, PyObject *v,\n+                  const formatdef *f)\n+{\n+    Py_complex c = PyComplex_AsCComplex(v);\n+    double complex x = CMPLX(c.real, c.imag);\n+\n+    if (c.real == -1 \u0026\u0026 PyErr_Occurred()) {\n+        PyErr_SetString(state-\u003eStructError,\n+                        \"required argument is not a complex\");\n+        return -1;\n+    }\n+    memcpy(p, (char *)\u0026x, sizeof(x));\n+    return 0;\n+}\n+#endif\n+\n static int\n np_void_p(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)\n {\n@@ -829,6 +867,9 @@ static const formatdef native_table[] = {\n     {'e',       sizeof(short),  SHORT_ALIGN,    nu_halffloat,   np_halffloat},\n     {'f',       sizeof(float),  FLOAT_ALIGN,    nu_float,       np_float},\n     {'d',       sizeof(double), DOUBLE_ALIGN,   nu_double,      np_double},\n+#ifdef Py_HAVE_C_COMPLEX\n+    {'C',       sizeof(double complex), DOUBLE_COMPLEX_ALIGN, nu_double_complex, np_double_complex},\n+#endif\n     {'P',       sizeof(void *), VOID_P_ALIGN,   nu_void_p,      np_void_p},\n     {0}\n };\n```\n\n\u003c/details\u003e\n\n### Has this already been discussed elsewhere?\n\nThis is a minor feature, which does not need previous discussion elsewhere\n\n### Links to previous discussion of this feature:\n\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-121613\n* gh-131867\n* gh-132827\n* gh-132863\n* gh-132864\n* gh-133249\n* gh-149346\n* gh-152274\n* gh-152309\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/skirpichev","@type":"Person","name":"skirpichev"},"datePublished":"2024-07-02T03:36:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":23},"url":"https://github.com/121249/cpython/issues/121249"}