Avoid type cheats for invalid dsa_handles and dshash_table_handles.

Invent separate macros for "invalid" values of these types, so that
we needn't embed knowledge of their representations into calling code.
These are all zeroes anyway ATM, so this is not fixing any live bug,
but it makes the code cleaner and more future-proof.

I (tgl) also chose to move DSM_HANDLE_INVALID into dsm_impl.h,
since it seems like it should live beside the typedef for dsm_handle.

Hou Zhijie, Nathan Bossart, Kyotaro Horiguchi, Tom Lane

Discussion: https://postgr.es/m/OS0PR01MB5716860B1454C34E5B179B6694C99@OS0PR01MB5716.jpnprd01.prod.outlook.com

diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 564bffe5caf20654520f981e494492da5e534afb..970d170e73aa18e7cd86f0206b0ec62978c397dd 100644 (file)
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -922,8 +922,8 @@ ApplyLauncherShmemInit(void)
 
        memset(LogicalRepCtx, 0, ApplyLauncherShmemSize());
 
-       LogicalRepCtx->last_start_dsa = DSM_HANDLE_INVALID;
-       LogicalRepCtx->last_start_dsh = DSM_HANDLE_INVALID;
+       LogicalRepCtx->last_start_dsa = DSA_HANDLE_INVALID;
+       LogicalRepCtx->last_start_dsh = DSHASH_HANDLE_INVALID;
 
        /* Initialize memory and spin locks for each worker slot. */
        for (slot = 0; slot < max_logical_replication_workers; slot++)
@@ -947,7 +947,7 @@ logicalrep_launcher_attach_dshmem(void)
    MemoryContext oldcontext;
 
    /* Quick exit if we already did this. */
-   if (LogicalRepCtx->last_start_dsh != DSM_HANDLE_INVALID &&
+   if (LogicalRepCtx->last_start_dsh != DSHASH_HANDLE_INVALID &&
        last_start_times != NULL)
        return;
 
@@ -957,7 +957,7 @@ logicalrep_launcher_attach_dshmem(void)
    /* Be sure any local memory allocated by DSA routines is persistent. */
    oldcontext = MemoryContextSwitchTo(TopMemoryContext);
 
-   if (LogicalRepCtx->last_start_dsh == DSM_HANDLE_INVALID)
+   if (LogicalRepCtx->last_start_dsh == DSHASH_HANDLE_INVALID)
    {
        /* Initialize dynamic shared hash table for last-start times. */
        last_start_times_dsa = dsa_create(LWTRANCHE_LAUNCHER_DSA);

diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c
index ba3ceb8153edff27e3b6d2886fe7fc9b542015c4..10b029bb162a1de07fc73e5b8c214a386e472234 100644 (file)
--- a/src/backend/storage/ipc/dsm.c
+++ b/src/backend/storage/ipc/dsm.c
@@ -173,9 +173,8 @@ dsm_postmaster_startup(PGShmemHeader *shim)
 
    /*
     * Loop until we find an unused identifier for the new control segment. We
-    * sometimes use 0 as a sentinel value indicating that no control segment
-    * is known to exist, so avoid using that value for a real control
-    * segment.
+    * sometimes use DSM_HANDLE_INVALID as a sentinel value indicating "no
+    * control segment", so avoid generating that value for a real handle.
     */
    for (;;)
    {

diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c
index 604b702a91fc451a4c49e5e680bee65190c96965..f5a62061a3e919d582df956dd69c1ebfeb429c34 100644 (file)
--- a/src/backend/utils/mmgr/dsa.c
+++ b/src/backend/utils/mmgr/dsa.c
@@ -505,7 +505,7 @@ dsa_create_in_place(void *place, size_t size,
 dsa_handle
 dsa_get_handle(dsa_area *area)
 {
-   Assert(area->control->handle != DSM_HANDLE_INVALID);
+   Assert(area->control->handle != DSA_HANDLE_INVALID);
    return area->control->handle;
 }
 
@@ -554,7 +554,7 @@ dsa_attach_in_place(void *place, dsm_segment *segment)
 {
    dsa_area   *area;
 
-   area = attach_internal(place, NULL, DSM_HANDLE_INVALID);
+   area = attach_internal(place, NULL, DSA_HANDLE_INVALID);
 
    /*
     * Clean up when the control segment detaches, if a containing DSM segment

diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index 152927742e8ba66a2f6cef73c69f4bb0d65f810c..ece5552122683fc16ca097eee965ed1f4fc557ea 100644 (file)
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -23,6 +23,9 @@ typedef struct dshash_table dshash_table;
 /* A handle for a dshash_table which can be shared with other processes. */
 typedef dsa_pointer dshash_table_handle;
 
+/* Sentinel value to use for invalid dshash_table handles. */
+#define DSHASH_HANDLE_INVALID ((dshash_table_handle) InvalidDsaPointer)
+
 /* The type for hash values. */
 typedef uint32 dshash_hash;
 

diff --git a/src/include/storage/dsm.h b/src/include/storage/dsm.h
index d84d835d843fe00265e5eed8952649144e42e83e..858bbf61c28d3f8298c35cd9cf49b9be9d5c2df2 100644 (file)
--- a/src/include/storage/dsm.h
+++ b/src/include/storage/dsm.h
@@ -19,9 +19,6 @@ typedef struct dsm_segment dsm_segment;
 
 #define DSM_CREATE_NULL_IF_MAXSEGMENTS         0x0001
 
-/* A sentinel value for an invalid DSM handle. */
-#define DSM_HANDLE_INVALID 0
-
 /* Startup and shutdown functions. */
 struct PGShmemHeader;          /* avoid including pg_shmem.h */
 extern void dsm_cleanup_using_control_segment(dsm_handle old_control_handle);

diff --git a/src/include/storage/dsm_impl.h b/src/include/storage/dsm_impl.h
index fade3a366878c25f7710d86a89b082334eaed1c4..daf07bd19cd6831430065fb7d2fdd6947547d470 100644 (file)
--- a/src/include/storage/dsm_impl.h
+++ b/src/include/storage/dsm_impl.h
@@ -54,6 +54,9 @@ extern PGDLLIMPORT int min_dynamic_shared_memory;
 /* A "name" for a dynamic shared memory segment. */
 typedef uint32 dsm_handle;
 
+/* Sentinel value to use for invalid DSM handles. */
+#define DSM_HANDLE_INVALID ((dsm_handle) 0)
+
 /* All the shared-memory operations we know about. */
 typedef enum
 {

diff --git a/src/include/utils/dsa.h b/src/include/utils/dsa.h
index 104386e6740a16eb924413dec455ca33e0a15d1c..3ce4ee300a567870d34dc9eabb56c1f561c5133b 100644 (file)
--- a/src/include/utils/dsa.h
+++ b/src/include/utils/dsa.h
@@ -99,6 +99,10 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
  */
 typedef dsm_handle dsa_handle;
 
+/* Sentinel value to use for invalid dsa_handles. */
+#define DSA_HANDLE_INVALID ((dsa_handle) DSM_HANDLE_INVALID)
+
+
 extern dsa_area *dsa_create(int tranche_id);
 extern dsa_area *dsa_create_in_place(void *place, size_t size,
                                     int tranche_id, dsm_segment *segment);