Add assertion to check the special size is sane before dereferencing it.

hlinnaka · hlinnaka · commit 302ac7f27197 · 2015-06-30T13:44:04.000+03:00
This seems useful to catch errors of the sort I just fixed, where
PageGetSpecialPointer is called before initializing the page.
diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h
@@ -304,6 +304,8 @@ typedef PageHeaderData *PageHeader;
 #define PageGetSpecialPointer(page) \
 ( \
 	AssertMacro(PageIsValid(page)), \
+	AssertMacro(((PageHeader) (page))->pd_special <= BLCKSZ), \
+	AssertMacro(((PageHeader) (page))->pd_special >= SizeOfPageHeaderData), \
 	(char *) ((char *) (page) + ((PageHeader) (page))->pd_special) \
 )
 

Original file line number	Diff line number	Diff line change
`@@ -304,6 +304,8 @@ typedef PageHeaderData *PageHeader;`
`304`	`304`	`#define PageGetSpecialPointer(page) \`
`305`	`305`	`( \`
`306`	`306`	`AssertMacro(PageIsValid(page)), \`
	`307`	`+ AssertMacro(((PageHeader) (page))->pd_special <= BLCKSZ), \`
	`308`	`+ AssertMacro(((PageHeader) (page))->pd_special >= SizeOfPageHeaderData), \`
`307`	`309`	`(char ) ((char ) (page) + ((PageHeader) (page))->pd_special) \`
`308`	`310`	`)`
`309`	`311`