From 4800b2ee95de8c92705fca720fca8899b8b4113b Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Tue, 8 Dec 2009 15:35:22 +0000
Subject: [PATCH] Avoid pointer aliasing in the allocSpace() routine in
 vdbeaux.c.

FossilOrigin-Name: d6ae27512229d95502c584b17bb2cbdba401f80a
---
 manifest      | 18 +++++++++---------
 manifest.uuid |  2 +-
 src/vdbeaux.c | 47 +++++++++++++++++++++++++----------------------
 3 files changed, 35 insertions(+), 32 deletions(-)

diff --git a/manifest b/manifest
index e0b0bb2bc5..797542a68b 100644
--- a/manifest
+++ b/manifest
@@ -1,8 +1,8 @@
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1
 
-C Begin\supdating\sAPI\sdocumentation\sto\suse\sthe\snew\sMD5-hash\sbased\s\nautomatic\srequirements\snumbering.\s\sComment\schanges\sonly.\s\sMany\ssimilar\nchanges\swill\sfollow.
-D 2009-12-08T15:16:54
+C Avoid\spointer\saliasing\sin\sthe\sallocSpace()\sroutine\sin\svdbeaux.c.
+D 2009-12-08T15:35:23
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in c5827ead754ab32b9585487177c93bb00b9497b3
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -216,7 +216,7 @@ F src/vdbe.c 5ed06318aac5d57849170a8bf39e807c22c5fedd
 F src/vdbe.h bea1f0cd530775bdb58a340265f3cf3ee920e9b2
 F src/vdbeInt.h d7ea821ac7813c9bea0fe87558c35e07b2c7c44d
 F src/vdbeapi.c bb128b819b9ef1a2ce211a36a6cb70a1643fa239
-F src/vdbeaux.c 6b9da05a16fbb52afd2bf0b3080087afdf16b6eb
+F src/vdbeaux.c 86d43cdf9615235e1def993a945dfaabc20ab079
 F src/vdbeblob.c 84f924700a7a889152aeebef77ca5f4e3875ffb4
 F src/vdbemem.c 1e16e3a16e55f4c3452834f0e041726021aa66e0
 F src/vdbetrace.c 864cef96919323482ebd9986f2132435115e9cc2
@@ -780,14 +780,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P 7b1cfd65a6f7c85ef8f6e4622973457cff9d007c
-R bc9b0ca13c1d42e3ef0f31c3eafc2706
+P 973c5c86eed31dcce54d14e71938f2e255f5f1c7
+R c570a97b0ffcfd39f4ed66f9f0662c03
 U drh
-Z d3399929cb27f5d1d2ae1fd2280572aa
+Z ee7e56c2d879987294a2e31ad1fde920
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1.4.6 (GNU/Linux)
 
-iD8DBQFLHm3toxKgR168RlERAqh0AJ42+WxiDaf+yXW7XeNGamk5NI4QnQCcD5Ck
-Um9oKXZSMb+HswKtI2ZkMrA=
-=dxuM
+iD8DBQFLHnI+oxKgR168RlERAn/LAJ9meRPYFG8kZK/fIyNChkghTUHQWgCdGqla
+K42FnTiSLRLIME8ykgShkdk=
+=3fbN
 -----END PGP SIGNATURE-----
diff --git a/manifest.uuid b/manifest.uuid
index 6d2bba6825..031286e928 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-973c5c86eed31dcce54d14e71938f2e255f5f1c7
\ No newline at end of file
+d6ae27512229d95502c584b17bb2cbdba401f80a
\ No newline at end of file
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index cccc547169..93b9c3f752 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -1254,11 +1254,15 @@ void sqlite3VdbeIOTraceSql(Vdbe *p){
 #endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */
 
 /*
-** Allocate space from a fixed size buffer.  Make *pp point to the
-** allocated space.  (Note:  pp is a char* rather than a void** to
-** work around the pointer aliasing rules of C.)  *pp should initially
-** be zero.  If *pp is not zero, that means that the space has already
-** been allocated and this routine is a noop.
+** Allocate space from a fixed size buffer and return a pointer to
+** that space.  If insufficient space is available, return NULL.
+**
+** The pBuf parameter is the initial value of a pointer which will
+** receive the new memory.  pBuf is normally NULL.  If pBuf is not
+** NULL, it means that memory space has already been allocated and that
+** this routine should not allocate any new memory.  When pBuf is not
+** NULL simply return pBuf.  Only allocate new memory space when pBuf
+** is NULL.
 **
 ** nByte is the number of bytes of space needed.
 **
@@ -1269,23 +1273,23 @@ void sqlite3VdbeIOTraceSql(Vdbe *p){
 ** to allocate.  If there is insufficient space in *ppFrom to satisfy the
 ** request, then increment *pnByte by the amount of the request.
 */
-static void allocSpace(
-  char *pp,            /* IN/OUT: Set *pp to point to allocated buffer */
+static void *allocSpace(
+  void *pBuf,          /* Where return pointer will be stored */
   int nByte,           /* Number of bytes to allocate */
   u8 **ppFrom,         /* IN/OUT: Allocate from *ppFrom */
   u8 *pEnd,            /* Pointer to 1 byte past the end of *ppFrom buffer */
   int *pnByte          /* If allocation cannot be made, increment *pnByte */
 ){
   assert( EIGHT_BYTE_ALIGNMENT(*ppFrom) );
-  if( (*(void**)pp)==0 ){
-    nByte = ROUND8(nByte);
-    if( &(*ppFrom)[nByte] <= pEnd ){
-      *(void**)pp = (void *)*ppFrom;
-      *ppFrom += nByte;
-    }else{
-      *pnByte += nByte;
-    }
+  if( pBuf ) return pBuf;
+  nByte = ROUND8(nByte);
+  if( &(*ppFrom)[nByte] <= pEnd ){
+    pBuf = (void*)*ppFrom;
+    *ppFrom += nByte;
+  }else{
+    *pnByte += nByte;
   }
+  return pBuf;
 }
 
 /*
@@ -1358,13 +1362,12 @@ void sqlite3VdbeMakeReady(
 
     do {
       nByte = 0;
-      allocSpace((char*)&p->aMem, nMem*sizeof(Mem), &zCsr, zEnd, &nByte);
-      allocSpace((char*)&p->aVar, nVar*sizeof(Mem), &zCsr, zEnd, &nByte);
-      allocSpace((char*)&p->apArg, nArg*sizeof(Mem*), &zCsr, zEnd, &nByte);
-      allocSpace((char*)&p->azVar, nVar*sizeof(char*), &zCsr, zEnd, &nByte);
-      allocSpace((char*)&p->apCsr, 
-                 nCursor*sizeof(VdbeCursor*), &zCsr, zEnd, &nByte
-      );
+      p->aMem = allocSpace(p->aMem, nMem*sizeof(Mem), &zCsr, zEnd, &nByte);
+      p->aVar = allocSpace(p->aVar, nVar*sizeof(Mem), &zCsr, zEnd, &nByte);
+      p->apArg = allocSpace(p->apArg, nArg*sizeof(Mem*), &zCsr, zEnd, &nByte);
+      p->azVar = allocSpace(p->azVar, nVar*sizeof(char*), &zCsr, zEnd, &nByte);
+      p->apCsr = allocSpace(p->apCsr, nCursor*sizeof(VdbeCursor*),
+                            &zCsr, zEnd, &nByte);
       if( nByte ){
         p->pFree = sqlite3DbMallocZero(db, nByte);
       }