Date: Mon, 03 Mar 2008 14:51:59 -0800 From: Xin LI <delphij@delphij.net> To: Alexandre Biancalana <biancalana@gmail.com> Cc: freebsd-stable@freebsd.org Subject: Re: AMD64 only Segmentation fault (was: 7-STABLE(AMD64)+Qmail-LDAP core dump) Message-ID: <47CC810F.5030807@delphij.net> In-Reply-To: <8e10486b0803031424x31556698qa1bd1bbab8e8376f@mail.gmail.com> References: <8e10486b0803031424x31556698qa1bd1bbab8e8376f@mail.gmail.com>
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Alexandre Biancalana wrote: > Hi list, > > I found a situation that I can't explain, I have qmail-ldap running > at some FreeBSD 6.2 without any problem. Friday after Installed a new > server this time with 7-STABLE. I stated to get core dumped from > qmail-ldap when they try access the OpenLDAP database. > > I compiled/run this simple C program in 7-STABLE i386 and AMD64 and > the program dumps the core only in AMD64. I have tried to reproduce the problem and have the following observations. To make a long story short, you *must* either use the new ldap_initialize API instead of the old one, or to define LDAP_DEPRECATED at the risk of having the program to break in the future, and *NOT* ignoring any warnings issued by the compiler. So here is the reason why we have a coredump. ldap_init is defined only when LDAP_DEPRECATED is defined, when ldap.h is included, and by default, C will assume that the return type is "int". On i386, this is not a problem because sizeof(int) equals to sizeof(void *), and the implicit cast would work; On amd64, we have sizeof(int) == 4 and sizeof(void *) == 8, by casting the result to int (because the header did not gave the type of ldap_init), and back (because of the assignment ld =), we lose 4 bytes (the high 32 bits) of the pointer, and therefore, when referring it we got a SEGV. This is one of the most common culprit when your 32-bit application "magically" broken on amd64 :-) Cheers, -- Xin LI <delphij@delphij.net> http://www.delphij.net/ FreeBSD - The Power to Serve!
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