database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-29 10:41:53 +03:00
Code Activity

Work around gcc 4.6.0 bug that breaks WAL replay.

Browse Source 
ReadRecord's habit of using both direct references to tmpRecPtr and
references to *RecPtr (which is pointing at tmpRecPtr) triggers an
optimization bug in gcc 4.6.0, which apparently has forgotten about
aliasing rules.  Avoid the compiler bug, and make the code more readable
to boot, by getting rid of the direct references.  Improve the comments
while at it.

Back-patch to all supported versions, in case they get built with 4.6.0.

Tom Lane, with some cosmetic suggestions from Alex Hunsaker
This commit is contained in:
Tom Lane
2011-06-10 17:03:21 -04:00
parent 376f93e0a1
commit 6ab58354df
1 changed files with 11 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
src/backend/access/transam/xlog.c
View File

@ -3041,12 +3041,12 @@ ReadRecord(XLogRecPtr *RecPtr, int emode)
goto got_record; goto got_record;
} }
/* align old recptr to next page */ /* align old recptr to next page */
if (tmpRecPtr.xrecoff % XLOG_BLCKSZ != 0) if (RecPtr->xrecoff % XLOG_BLCKSZ != 0)
tmpRecPtr.xrecoff += (XLOG_BLCKSZ - tmpRecPtr.xrecoff % XLOG_BLCKSZ); RecPtr->xrecoff += (XLOG_BLCKSZ - RecPtr->xrecoff % XLOG_BLCKSZ);
if (tmpRecPtr.xrecoff >= XLogFileSize) if (RecPtr->xrecoff >= XLogFileSize)
{ {
(tmpRecPtr.xlogid)++; (RecPtr->xlogid)++;
tmpRecPtr.xrecoff = 0; RecPtr->xrecoff = 0;
} }
/* We will account for page header size below */ /* We will account for page header size below */
} }
@ -3132,11 +3132,13 @@ ReadRecord(XLogRecPtr *RecPtr, int emode)
if (targetRecOff == 0) if (targetRecOff == 0)
{ {
/* /*
* Can only get here in the continuing-from-prev-page case, because * At page start, so skip over page header. The Assert checks that
* XRecOffIsValid eliminated the zero-page-offset case otherwise. Need * we're not scribbling on caller's record pointer; it's OK because we
* to skip over the new page's header. * can only get here in the continuing-from-prev-record case, since
* XRecOffIsValid rejected the zero-page-offset case otherwise.
*/ */
tmpRecPtr.xrecoff += pageHeaderSize; Assert(RecPtr == &tmpRecPtr);
RecPtr->xrecoff += pageHeaderSize;
targetRecOff = pageHeaderSize; targetRecOff = pageHeaderSize;
} }
else if (targetRecOff < pageHeaderSize) else if (targetRecOff < pageHeaderSize)