> Afternoon all,
>
> I have been working on a Firebird Internals manual for some time, and it
> was built with the help of a small tool I wrote to dump out specific
> pages from a database. The structs for each page were blatantly copied
> from jrd/ods.h and when I compiled my app back then (ahem, 2009!) my gcc
> version was 4.1.2 and all worked fine.
>
> On my own laptop I have gcc version 4.6.3 and I'm getting complete
> garbage with the same source code.
>
> I suspect I'm falling foul of some gcc alignment/padding thing and I'm
> wondering if anyone could point me in the right direction?
>
> At present I compile with a simple "gcc -o fbdump fbdump.c" and that's
> the same on the old system and my laptop (exactly the same source.)
>
> As an example of how wrong it can be, here's a Firebird 2.5 employee
> page header showing all sorts of errors:
>
> FBDUMP 1.00 - Firebird Page Dump Utility
>
> Parameters : -v -p 0
> Database: /var/lib/firebird/2.5/data/employee.fdb
>
> DATABASE PAGE DETAILS - Page 0
> PAGE HEADER
> Page Type: 1
> Flags: 0
> Checksum: 12345
> Generation: 0
> SCN: 15033110528
> Reserved: 2993592205312
> PAGE DATA
> Database Page Size: 698
> ODS Version: 0
> Pages: 240028567601152
> Next Page: 348481045616
> Oldest Transaction: 563031557799936
> Oldest Active: 6291458
> Next Transaction: 2997887172609
> Sequence: 0
> Flags: 0
> Creation Date: COMING SOON
> Attachment Id: 0
> Shadow Count: 0
> Implementation: 0
> ODS minor: 0
> ODS minororiginal: 0
> HDR_END: 0
> Page Buffers: 0
> Bumped Transaction: 0
> Oldest Snapshot: 0
> Backup Pages: 0
>
> A straight hexdump of the first page is as follows:
>
> 0000 01 00 39 30 c8 02 00 00 00 00 00 00 00 00 00 00
> 0010 00 10 0b 80 03 00 00 00 00 00 00 00 b9 02 00 00
> 0020 ba 02 00 00 bb 02 00 00 00 00 82 01 4e da 00 00
> 0030 70 c4 16 23 51 00 00 00 00 00 00 00 13 00 02 00
> 0040 02 00 60 00 00 00 00 00 01 00 00 00 ba 02 00 00
> 0050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>
> And finally, how the header page is defined in the utility:
>
> // Page Header - on every page type.
> typedef struct
> {
> SCHAR pag_type;
> UCHAR pag_flags;
> USHORT pag_checksum;
> ULONG pag_generation;
> ULONG pag_scn;
> ULONG pag_reserved;
> } pageHeader;
Looks like your ULONG is 8-byte integer while it shold be 4-byte.
Regards,
Vlad
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