I propose to add an equivalent to unconstify() for volatile. When
working on this, I picked the name unvolatize() mostly as a joke, but it
appears it's a real word. Other ideas?
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From e2275c87f644b30b92434020adc8e2f7892a8e9c Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Mon, 18 Feb 2019 16:08:41 +0100
Subject: [PATCH] Add macro to cast away volatile without allowing changes to
underlying type
This adds unvolatize(), which works just like unconstify() but for volatile.
---
contrib/dblink/dblink.c | 2 +-
contrib/hstore_plpython/hstore_plpython.c | 6 +++---
contrib/jsonb_plpython/jsonb_plpython.c | 4 ++--
src/backend/postmaster/pgstat.c | 2 +-
src/backend/storage/ipc/latch.c | 2 +-
src/backend/storage/ipc/pmsignal.c | 2 +-
src/include/c.h | 8 +++++++-
7 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index d95e6bfa71..402a692191 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -988,7 +988,7 @@ materializeQueryResult(FunctionCallInfo fcinfo,
Assert(rsinfo->returnMode == SFRM_Materialize);
/* initialize storeInfo to empty */
- memset((void *) &sinfo, 0, sizeof(sinfo));
+ memset(unvolatize(storeInfo *, &sinfo), 0, sizeof(sinfo));
sinfo.fcinfo = fcinfo;
PG_TRY();
diff --git a/contrib/hstore_plpython/hstore_plpython.c
b/contrib/hstore_plpython/hstore_plpython.c
index 2f24090ff3..beb201f635 100644
--- a/contrib/hstore_plpython/hstore_plpython.c
+++ b/contrib/hstore_plpython/hstore_plpython.c
@@ -146,7 +146,7 @@ plpython_to_hstore(PG_FUNCTION_ARGS)
int32 buflen;
int32 i;
Pairs *pairs;
- PyObject *items = (PyObject *) items_v;
+ PyObject *items = unvolatize(PyObject *, items_v);
pairs = palloc(pcount * sizeof(*pairs));
@@ -177,14 +177,14 @@ plpython_to_hstore(PG_FUNCTION_ARGS)
pairs[i].isnull = false;
}
}
- Py_DECREF(items_v);
+ Py_DECREF(items);
pcount = hstoreUniquePairs(pairs, pcount, &buflen);
out = hstorePairs(pairs, pcount, buflen);
}
PG_CATCH();
{
- Py_DECREF(items_v);
+ Py_DECREF(unvolatize(PyObject *, items_v));
PG_RE_THROW();
}
PG_END_TRY();
diff --git a/contrib/jsonb_plpython/jsonb_plpython.c
b/contrib/jsonb_plpython/jsonb_plpython.c
index f44d364c97..f860e7bc76 100644
--- a/contrib/jsonb_plpython/jsonb_plpython.c
+++ b/contrib/jsonb_plpython/jsonb_plpython.c
@@ -247,7 +247,7 @@ PLyMapping_ToJsonbValue(PyObject *obj, JsonbParseState
**jsonb_state)
Py_ssize_t i;
PyObject *items;
- items = (PyObject *) items_v;
+ items = unvolatize(PyObject *, items_v);
pushJsonbValue(jsonb_state, WJB_BEGIN_OBJECT, NULL);
@@ -279,7 +279,7 @@ PLyMapping_ToJsonbValue(PyObject *obj, JsonbParseState
**jsonb_state)
}
PG_CATCH();
{
- Py_DECREF(items_v);
+ Py_DECREF(unvolatize(PyObject *, items_v));
PG_RE_THROW();
}
PG_END_TRY();
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 81c6499251..84ebe03284 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3275,7 +3275,7 @@ pgstat_read_current_status(void)
localentry->backendStatus.st_procpid =
beentry->st_procpid;
if (localentry->backendStatus.st_procpid > 0)
{
- memcpy(&localentry->backendStatus, (char *)
beentry, sizeof(PgBackendStatus));
+ memcpy(&localentry->backendStatus,
unvolatize(PgBackendStatus *, beentry), sizeof(PgBackendStatus));
/*
* strcpy is safe even if the string is
modified concurrently,
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index 7da337d11f..fa7d72ef76 100644
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -381,7 +381,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents,
pgsocket sock,
if (wakeEvents & WL_LATCH_SET)
AddWaitEventToSet(set, WL_LATCH_SET, PGINVALID_SOCKET,
- (Latch *) latch, NULL);
+ unvolatize(Latch *, latch),
NULL);
/* Postmaster-managed callers must handle postmaster death somehow. */
Assert(!IsUnderPostmaster ||
diff --git a/src/backend/storage/ipc/pmsignal.c
b/src/backend/storage/ipc/pmsignal.c
index d707993bf6..48f4311464 100644
--- a/src/backend/storage/ipc/pmsignal.c
+++ b/src/backend/storage/ipc/pmsignal.c
@@ -134,7 +134,7 @@ PMSignalShmemInit(void)
if (!found)
{
- MemSet(PMSignalState, 0, PMSignalShmemSize());
+ MemSet(unvolatize(PMSignalData *, PMSignalState), 0,
PMSignalShmemSize());
PMSignalState->num_child_flags = MaxLivePostmasterChildren();
}
}
diff --git a/src/include/c.h b/src/include/c.h
index 3ea748ff58..a2f3c961d4 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1122,7 +1122,7 @@ typedef union PGAlignedXLogBlock
#endif
/*
- * Macro that allows to cast constness away from an expression, but doesn't
+ * Macro that allows to cast constness and volatile away from an expression,
but doesn't
* allow changing the underlying type. Enforcement of the latter
* currently only works for gcc like compilers.
*
@@ -1141,9 +1141,15 @@ typedef union PGAlignedXLogBlock
(StaticAssertExpr(__builtin_types_compatible_p(__typeof(expr), const
underlying_type), \
"wrong cast"), \
(underlying_type) (expr))
+#define unvolatize(underlying_type, expr) \
+ (StaticAssertExpr(__builtin_types_compatible_p(__typeof(expr), volatile
underlying_type), \
+ "wrong cast"), \
+ (underlying_type) (expr))
#else
#define unconstify(underlying_type, expr) \
((underlying_type) (expr))
+#define unvolatize(underlying_type, expr) \
+ ((underlying_type) (expr))
#endif
/* ----------------------------------------------------------------
--
2.20.1
