Omit the (undocumented) SQLITE_PCACHE_SEPARATE_HEADER compile-time option.

FossilOrigin-Name: 60947da687d525e72e62bcddcdf4c5c819818855074cc318c9ee656e83897aef

manifest

@@ -1,5 +1,5 @@
-C Avoid\ssome\scases\sof\ssigned\sinteger\soverflow\sin\sfts5\sby\scasting\sto\sunsigned\svalues.
+C Omit\sthe\s(undocumented)\sSQLITE_PCACHE_SEPARATE_HEADER\scompile-time\soption.
-D 2022-08-08T19:29:53.445
+D 2022-08-09T14:28:54.231
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -517,7 +517,7 @@ F src/btreeInt.h 8ce1332edd89dfd2461d561ac10a0ab5601c8e06200cb5230596c3caaf54482
 F src/build.c 33aec2b34dbc53c3da2ea8434fccbf3c17c35ba647c3193df598cce0e861355c
 F src/callback.c 4c19af69835787bfe790ac560f3071a824eb629f34e41f97b52ce5235c77de1c
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
-F src/ctime.c 026dbdcdbd8c3cde98a88483ee88310ff43150ab164ad768f12cc700a11495ad
+F src/ctime.c 93e4b5f4faf6d3f688988a116773259a4fbfb4ddac0e9bf9d0ae0429390c2543
 F src/date.c 94ce83b4cd848a387680a5f920c9018c16655db778c4d36525af0a0f34679ac5
 F src/dbpage.c 5808e91bc27fa3981b028000f8fadfdc10ce9e59a34ce7dc4e035a69be3906ec
 F src/dbstat.c 861e08690fcb0f2ee1165eff0060ea8d4f3e2ea10f80dab7d32ad70443a6ff2d
@@ -563,7 +563,7 @@ F src/pager.h f82e9844166e1585f5786837ddc7709966138ced17f568c16af7ccf946c2baa3
 F src/parse.y 8e67d820030d2655b9942ffe61c1e7e6b96cea2f2f72183533299393907d0564
 F src/pcache.c 084e638432c610f95aea72b8509f0845d2791293f39d1b82f0c0a7e089c3bb6b
 F src/pcache.h 4f87acd914cef5016fae3030343540d75f5b85a1877eed1a2a19b9f284248586
-F src/pcache1.c 54881292a9a5db202b2c0ac541c5e3ef9a5e8c4f1c1383adb2601d5499a60e65
+F src/pcache1.c 0b4245cd4964e635f2630908c2533cd8e9da7af3ca592e23ae8730aa25ae5eb9
 F src/pragma.c 6637d624c37a8909d3edfa9d7cf694d79b49d2a0827d8c52ef15dceb641783fa
 F src/pragma.h e690a356c18e98414d2e870ea791c1be1545a714ba623719deb63f7f226d8bb7
 F src/prepare.c c62820c15dcb63013519c8e41d9f928d7478672cc902cfd0581c733c271dbf45
@@ -1909,7 +1909,7 @@ F tool/max-limits.c cbb635fbb37ae4d05f240bfb5b5270bb63c54439
 F tool/merge-test.tcl de76b62f2de2a92d4c1ca4f976bce0aea6899e0229e250479b229b2a1914b176
 F tool/mkautoconfamal.sh f62353eb6c06ab264da027fd4507d09914433dbdcab9cb011cdc18016f1ab3b8
 F tool/mkccode.tcl 86463e68ce9c15d3041610fedd285ce32a5cf7a58fc88b3202b8b76837650dbe x
-F tool/mkctimec.tcl ac96a74f5e6d9dac672d5229f79c583d3357a50e7d098e473e6b2ce2f8ae1704 x
+F tool/mkctimec.tcl 8f472681f6041cf0ec26a1799feda39e55370614a6090d66fa5044f9f52d22c6 x
 F tool/mkkeywordhash.c 35bfc41adacc4aa6ef6fca7fd0c63e0ec0534b78daf4d0cfdebe398216bbffc3
 F tool/mkmsvcmin.tcl 6ecab9fe22c2c8de4d82d4c46797bda3d2deac8e763885f5a38d0c44a895ab33
 F tool/mkopcodec.tcl 33d20791e191df43209b77d37f0ff0904620b28465cca6990cf8d60da61a07ef
@@ -1982,8 +1982,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 3518cd7cb1feeefc3963da72c2d258d81d8914f1e1f427da28a00b6228cf126c
+P 46a78c8c0ed518c4521e6e0bdebeb065bab07076abc444775002e7f4361d2242
-R ee3441acc635032c89c4a495f8aff56d
+R d8bef198132a525587d2454d35cbc1ca
-U dan
+U drh
-Z 869f3966f913fbed35d61b23d360896d
+Z a9046e25d51003cb689d3e1458ccf6d6
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-46a78c8c0ed518c4521e6e0bdebeb065bab07076abc444775002e7f4361d2242
+60947da687d525e72e62bcddcdf4c5c819818855074cc318c9ee656e83897aef

src/ctime.c

@@ -683,9 +683,6 @@ static const char * const sqlite3azCompileOpt[] = {
 #ifdef SQLITE_OMIT_XFER_OPT
   "OMIT_XFER_OPT",
 #endif
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-  "PCACHE_SEPARATE_HEADER",
-#endif
 #ifdef SQLITE_PERFORMANCE_TRACE
   "PERFORMANCE_TRACE",
 #endif

src/pcache1.c

@@ -39,12 +39,13 @@
 ** size can vary according to architecture, compile-time options, and
 ** SQLite library version number.
 **
-** If SQLITE_PCACHE_SEPARATE_HEADER is defined, then the extension is obtained
+** Historical note:  It used to be that if the SQLITE_PCACHE_SEPARATE_HEADER
-** using a separate memory allocation from the database page content.  This
+** was defined, then the page content would be held in a separate memory
-** seeks to overcome the "clownshoe" problem (also called "internal
+** allocation from the PgHdr1.  This was intended to avoid clownshoe memory
-** fragmentation" in academic literature) of allocating a few bytes more
+** allocations.  However, the btree layer needs a small (16-byte) overrun
-** than a power of two with the memory allocator rounding up to the next
+** area after the page content buffer.  The header serves as that overrun
-** power of two, and leaving the rounded-up space unused.
+** area.  Therefore SQLITE_PCACHE_SEPARATE_HEADER was discontinued to avoid
+** any possibility of a memory error.
 **
 ** This module tracks pointers to PgHdr1 objects.  Only pcache.c communicates
 ** with this module.  Information is passed back and forth as PgHdr1 pointers.
@@ -89,11 +90,16 @@ typedef struct PGroup PGroup;
 
 /*
 ** Each cache entry is represented by an instance of the following 
-** structure. Unless SQLITE_PCACHE_SEPARATE_HEADER is defined, a buffer of
+** structure. A buffer of PgHdr1.pCache->szPage bytes is allocated
-** PgHdr1.pCache->szPage bytes is allocated directly before this structure 
+** directly before this structure and is used to cache the page content.
-** in memory.
 **
-** Note: Variables isBulkLocal and isAnchor were once type "u8". That works,
+** When reading a corrupt database file, it is possible that SQLite might
+** read a few bytes (no more than 16 bytes) past the end of the page buffer.
+** It will only read past the end of the page buffer, never write.  This
+** object is positioned immediately after the page buffer to serve as an
+** overrun area, so that overreads are harmless.
+**
+** Variables isBulkLocal and isAnchor were once type "u8". That works,
 ** but causes a 2-byte gap in the structure for most architectures (since 
 ** pointers must be either 4 or 8-byte aligned). As this structure is located
 ** in memory directly after the associated page data, if the database is
@@ -438,25 +444,13 @@ static PgHdr1 *pcache1AllocPage(PCache1 *pCache, int benignMalloc){
     pcache1LeaveMutex(pCache->pGroup);
 #endif
     if( benignMalloc ){ sqlite3BeginBenignMalloc(); }
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-    pPg = pcache1Alloc(pCache->szPage);
-    p = sqlite3Malloc(sizeof(PgHdr1) + pCache->szExtra);
-    if( !pPg || !p ){
-      pcache1Free(pPg);
-      sqlite3_free(p);
-      pPg = 0;
-    }
-#else
     pPg = pcache1Alloc(pCache->szAlloc);
-#endif
     if( benignMalloc ){ sqlite3EndBenignMalloc(); }
 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
     pcache1EnterMutex(pCache->pGroup);
 #endif
     if( pPg==0 ) return 0;
-#ifndef SQLITE_PCACHE_SEPARATE_HEADER
     p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
-#endif
     p->page.pBuf = pPg;
     p->page.pExtra = &p[1];
     p->isBulkLocal = 0;
@@ -480,9 +474,6 @@ static void pcache1FreePage(PgHdr1 *p){
     pCache->pFree = p;
   }else{
     pcache1Free(p->page.pBuf);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-    sqlite3_free(p);
-#endif
   }
   (*pCache->pnPurgeable)--;
 }
@@ -1246,9 +1237,6 @@ int sqlite3PcacheReleaseMemory(int nReq){
        &&  p->isAnchor==0
     ){
       nFree += pcache1MemSize(p->page.pBuf);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-      nFree += sqlite3MemSize(p);
-#endif
       assert( PAGE_IS_UNPINNED(p) );
       pcache1PinPage(p);
       pcache1RemoveFromHash(p, 1);

tool/mkctimec.tcl

@@ -254,7 +254,6 @@ set boolean_defnil_options {
   SQLITE_OMIT_WAL
   SQLITE_OMIT_WSD
   SQLITE_OMIT_XFER_OPT
-  SQLITE_PCACHE_SEPARATE_HEADER
   SQLITE_PERFORMANCE_TRACE
   SQLITE_PREFER_PROXY_LOCKING
   SQLITE_PROXY_DEBUG