Fixed bug #192 (Decimal support not safe for use with multiple sub

interpreters) as proposed by Graham Dumpleton.

If running in the main interpreter, use a cached version of the Decimal
object. Else repeat the object lookup.

4 files changed, 66 insertions, 10 deletions

diff --git a/ChangeLog b/ChangeLog
index 8a48e92..302bb5b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,9 @@
-2007-09-08  Federico Di Gregorio <fog@initd.org>
+2007-10-21  Daniele Varrazzo  <daniele.varrazzo@gmail.com>
+
+	* Fixed bug #192 (Decimal support not safe for use with multiple sub
+	  interpreters) as proposed by Graham Dumpleton.
+
+2007-09-08  Federico Di Gregorio  <fog@initd.org>
 
 	* Added MonoDevelop project, yahi!
 
diff --git a/psycopg/psycopg.h b/psycopg/psycopg.h
index aeb174c..945ce92 100644
--- a/psycopg/psycopg.h
+++ b/psycopg/psycopg.h
@@ -130,7 +130,7 @@ typedef struct {
 } encodingPair;
 
 /* the Decimal type, used by the DECIMAL typecaster */
-extern PyObject *decimalType;
+extern PyObject *psyco_GetDecimalType(void);
 
 /* some utility functions */
 extern void psyco_set_error(PyObject *exc, PyObject *curs,  char *msg,
diff --git a/psycopg/psycopgmodule.c b/psycopg/psycopgmodule.c
index ee4bc8e..53fd641 100644
--- a/psycopg/psycopgmodule.c
+++ b/psycopg/psycopgmodule.c
@@ -62,7 +62,6 @@ PyObject *pyPsycopgTzLOCAL = NULL;
 PyObject *pyPsycopgTzFixedOffsetTimezone = NULL;
 
 PyObject *psycoEncodings = NULL;
-PyObject *decimalType = NULL;
 
 /** connect module-level function **/
 #define psyco_connect_doc \
@@ -330,7 +329,8 @@ psyco_adapters_init(PyObject *mod)
 #endif
 
 #ifdef HAVE_DECIMAL
-    microprotocols_add((PyTypeObject*)decimalType, NULL, (PyObject*)&asisType);
+    microprotocols_add((PyTypeObject*)psyco_GetDecimalType(),
+                       NULL, (PyObject*)&asisType);
 #endif
 }
 
@@ -554,14 +554,55 @@ psyco_set_error(PyObject *exc, PyObject *curs, char *msg,
     }
 }
 
-/* psyco_decimal_init
 
-   Initialize the module's pointer to the decimal type. */
+/* Return nonzero if the current one is the main interpreter */
+static int
+psyco_is_main_interp()
+{
+    static PyInterpreterState *main_interp = NULL;  /* Cached reference */
+    PyInterpreterState *interp;
 
-void
-psyco_decimal_init(void)
+    if (main_interp) {
+        return (main_interp == PyThreadState_Get()->interp);
+    }
+
+    /* No cached value: cache the proper value and try again. */
+    interp = PyInterpreterState_Head();
+    while (interp->next)
+        interp = interp->next;
+
+    main_interp = interp;
+    assert (main_interp);
+    return psyco_is_main_interp();
+}
+
+
+/* psyco_GetDecimalType
+
+   Return a new reference to the adapter for decimal type.
+
+   If decimals should be used but the module import fails, fall back on
+   the float type.
+
+    If decimals are not to be used, return NULL.
+   */
+
+PyObject *
+psyco_GetDecimalType(void)
 {
+    PyObject *decimalType = NULL;
+    static PyObject *cachedType = NULL;
+
 #ifdef HAVE_DECIMAL
+
+    /* Use the cached object if running from the main interpreter. */
+    int can_cache = psyco_is_main_interp();
+    if (can_cache && cachedType) {
+        Py_INCREF(cachedType);
+        return cachedType;
+    }
+
+    /* Get a new reference to the Decimal type. */
     PyObject *decimal = PyImport_ImportModule("decimal");
     if (decimal) {
         decimalType = PyObject_GetAttrString(decimal, "Decimal");
@@ -572,7 +613,15 @@ psyco_decimal_init(void)
         decimalType = (PyObject *)&PyFloat_Type;
         Py_INCREF(decimalType);
     }
-#endif
+
+    /* Store the object from future uses. */
+    if (can_cache && !cachedType) {
+        cachedType = decimalType;
+    }
+
+#endif /* HAVE_DECIMAL */
+
+    return decimalType;
 }
 
 
@@ -731,7 +780,6 @@ init_psycopg(void)
     /* other mixed initializations of module-level variables */
     psycoEncodings = PyDict_New();
     psyco_encodings_fill(psycoEncodings);
-    psyco_decimal_init();
 
     /* set some module's parameters */
     PyModule_AddStringConstant(module, "__version__", PSYCOPG_VERSION);
diff --git a/psycopg/typecast_basic.c b/psycopg/typecast_basic.c
index 2bc9718..eeb96be 100644
--- a/psycopg/typecast_basic.c
+++ b/psycopg/typecast_basic.c
@@ -120,6 +120,7 @@ static PyObject *
 typecast_DECIMAL_cast(char *s, Py_ssize_t len, PyObject *curs)
 {
     PyObject *res = NULL;
+    PyObject *decimalType;
     char *buffer;
 
     if (s == NULL) {Py_INCREF(Py_None); return Py_None;}
@@ -127,7 +128,9 @@ typecast_DECIMAL_cast(char *s, Py_ssize_t len, PyObject *curs)
     if ((buffer = PyMem_Malloc(len+1)) == NULL)
         return PyErr_NoMemory();
     strncpy(buffer, s, (size_t) len); buffer[len] = '\0';
+    decimalType = psyco_GetDecimalType();
     res = PyObject_CallFunction(decimalType, "s", buffer);
+    Py_DECREF(decimalType);
     PyMem_Free(buffer);
 
     return res;