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

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
index c2fbffc8e9b72c71addab4a4ad028792d38c70a8..a2f78ee56ce9e8c045b0a6b3bfd639a92fa8959d 100644 (file)
--- 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) \
 )