Require superuser privilege to create a binary-compatible cast, per

discussion some weeks ago.  Also, add a check that two types to be
binary-equivalenced match as to typlen, typbyval, and typalign; if
they don't then it's surely a mistake to equivalence them.

diff --git a/doc/src/sgml/ref/create_cast.sgml b/doc/src/sgml/ref/create_cast.sgml
index e64d696f81afc9ee11d966e627d54dae1e90318f..172b988a6af474ea51eb98c43b23cebb6f3445c2 100644 (file)
--- a/doc/src/sgml/ref/create_cast.sgml
+++ b/doc/src/sgml/ref/create_cast.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  
@@ -81,10 +81,9 @@ SELECT 'The time is ' || now();
 
    will be allowed only if the cast from type timestamp to
    text is marked AS IMPLICIT.  Otherwise it
-   will be necessary to write one of
+   will be necessary to write the cast explicitly, for example
 
 SELECT 'The time is ' || CAST(now() AS text);
-SELECT 'The time is ' || now()::text;
 
    (We generally use the term implicit
    cast to describe this kind of cast.)
@@ -107,7 +106,9 @@ SELECT 'The time is ' || now()::text;
 
   
    To be able to create a cast, you must own the source or the target
-   data type.
+   data type.  To create a binary-compatible cast, you must be superuser
+   (this restriction is made because an erroneous binary-compatible cast
+   conversion can easily crash the server).
   
 
    

diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index 7857eb3bb3fea155ed272f8d078f7130be8f4d78..01217d9b1283408ca2b7b57b7e54ad19f1c7cccd 100644 (file)
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/commands/functioncmds.c,v 1.22 2002/09/21 18:39:25 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/commands/functioncmds.c,v 1.23 2002/10/04 22:08:44 tgl Exp $
  *
  * DESCRIPTION
  *   These routines take the parse tree and pick out the
@@ -756,8 +756,35 @@ CreateCast(CreateCastStmt *stmt)
    }
    else
    {
+       int16   typ1len;
+       int16   typ2len;
+       bool    typ1byval;
+       bool    typ2byval;
+       char    typ1align;
+       char    typ2align;
+
        /* indicates binary coercibility */
        funcid = InvalidOid;
+
+       /*
+        * Must be superuser to create binary-compatible casts, since
+        * erroneous casts can easily crash the backend.
+        */
+       if (!superuser())
+           elog(ERROR, "Must be superuser to create a cast WITHOUT FUNCTION");
+
+       /*
+        * Also, insist that the types match as to size, alignment, and
+        * pass-by-value attributes; this provides at least a crude check
+        * that they have similar representations.  A pair of types that
+        * fail this test should certainly not be equated.
+        */
+       get_typlenbyvalalign(sourcetypeid, &typ1len, &typ1byval, &typ1align);
+       get_typlenbyvalalign(targettypeid, &typ2len, &typ2byval, &typ2align);
+       if (typ1len != typ2len ||
+           typ1byval != typ2byval ||
+           typ1align != typ2align)
+           elog(ERROR, "source and target datatypes are not physically compatible");
    }
 
    /* convert CoercionContext enum to char value for castcontext */