[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
-- rguenth at gcc dot gnu dot org changed: What|Removed |Added Target Milestone|4.3.4 |--- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
-- pinskia at gcc dot gnu dot org changed: What|Removed |Added CC||pinskia at gcc dot gnu dot ||org Target Milestone|--- |4.3.4 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
--- Comment #8 from pinskia at gcc dot gnu dot org 2008-12-21 22:48 --- Does compiling with -O2 -fno-strict-aliasing fix the issue. I thought I saw some aliasing violations in the source dealing with accessing a char * as a Log_event::Byte* (aka unsigned char *). Now what is only defined is the accessing anything by a char/unsigned char/signed char, accessing pointers via a different type is undefined. The function which I saw the issue is in copy_str_and_move where there are going to be accesses in those two types. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
--- Comment #9 from kees at outflux dot net 2008-12-22 01:01 --- Yes! Adding -fno-strict-aliasing to a normal (-O2) build seems to have fixed the problems so far. The full test suite takes a while, but the early failures are not present any more. I will report more once it finishes. Thank you for the hint! Is this a regression in gcc, or is this something upstreams need to add to their builds when doing the char/pointer manipulations you described? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
--- Comment #10 from pinskia at gcc dot gnu dot org 2008-12-22 01:06 --- (In reply to comment #9) Is this a regression in gcc, or is this something upstreams need to add to their builds when doing the char/pointer manipulations you described? Most likely a bug in the mysql sources. Does compiling with -W -Wall produce any warnings (when compiling with just -O2)? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
--- Comment #11 from pinskia at gcc dot gnu dot org 2008-12-22 01:10 --- I do get a warning from the trunk though: log_event.cc: In member function 'virtual bool Query_log_event::write(IO_CACHE*)': log_event.cc:1124: warning: dereferencing pointer 'start.519' does break strict-aliasing rules log_event.cc:1217: note: initialized from here Which is exactly what I mentioned except it is a different place I was thinking of: write_str_with_code_and_len((char **)(start), catalog, catalog_len, 6); Yes this is now becomes an obvious aliasing issue as you are a unsigned char * as a char * which violates C/C++ aliasing rules. Please report this bug to mysql. -- pinskia at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution||INVALID http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
[Bug c++/38562] [4.3/4.4 regression] mysql miscompiles and causes testsuite failures
--- Comment #7 from kees at outflux dot net 2008-12-18 01:07 --- Created an attachment (id=16925) -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16925action=view) 4.4.0 -E output of log_event.cc (bzip2) $ /usr/lib/gcc-snapshot/bin/g++ -DMYSQL_SERVER -DDEFAULT_MYSQL_HOME=\/usr\ -DDATADIR=\/var/lib/mysql\ -DSHAREDIR=\/usr/share/mysql\ -DHAVE_CONFIG_H -I. -I. -I../include -I../innobase/include -I../innobase/include -I../ndb/include -I../ndb/include -I../ndb/include/ndbapi -I../ndb/include/mgmapi -I../include -I../include -I../regex -I. -DDBUG_OFF -DBIG_JOINS=1 -felide-constructors -fno-rtti -O1 -fno-implicit-templates -fno-exceptions -fno-rtti -MT log_event.o -MD -MP -MF .deps/log_event.Tpo -E log_event.cc /tmp/log_event.cc-E -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38562
