Date: Thu, 17 May 2012 15:15:33 -0700 From: Sean Bruno <seanbru@yahoo-inc.com> To: "chet.ramey@case.edu" <chet.ramey@case.edu> Cc: Craig Rodrigues <rodrigc@crodrigues.org>, Current FreeBSD <freebsd-current@freebsd.org> Subject: Re: ports/bash4 --enable-static fails Message-ID: <1337292933.15253.6.camel@powernoodle-l7.corp.yahoo.com> In-Reply-To: <4FABBB1B.4080108@case.edu> References: <1336599447.71431.2.camel@powernoodle-l7> <CAG=rPVdwu-k4bKNXBHuv47TL-90CrB_hV9ivzhD9E1LZhcRzig@mail.gmail.com> <4FABBB1B.4080108@case.edu>
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On Thu, 2012-05-10 at 05:56 -0700, Chet Ramey wrote: > On 5/10/12 12:20 AM, Craig Rodrigues wrote: > > > Bash is trying to override the malloc() functions in libc with its own > > implementation in lib/malloc/malloc.c . > > I have seen this type of trick before 3rd party code that tries to > > override the libc implementation of malloc() / free() with its own. > > > > kan@ explained this to me before, but I don't know if I can explain it > > as well as him, because it has to do > > with how static linking works. :) > > > > Basically, the malloc.o object from bash, *must* have implementations of > > *all* the relevant functions in jemalloc_jemalloc.o in order for > > malloc.o to properly override jemalloc_jemalloc.o. > > > > If you have something like: > > jemalloc_jemalloc.o (libc) malloc.o (Bash) > > =============== ============= > > malloc() malloc() > > free() free() > > calloc() > > realloc() > > > > > > the static linker will not be able to replace jemalloc_jemalloc.o from > > libc with malloc.o from Bash, > > because calloc() and realloc() symbols in jemalloc_jemalloc.o (libc) > > do not exist malloc.o (Bash). > > > > Since the linker can only deal with whole objects (.o files), it will > > try to pull in both > > jemalloc_jemalloc.o and malloc.o when doing static linking. > > > > I may have got some of the details/explanation wrong, but I have fixed > > something similar > > to this in 3rd party code, when the layout of malloc() functions in > > libc changed between FreeBSD 4 and FreeBSD 6. > > This explanation is substantially correct. > > > > > What you need to do is: > > (1) run nm or readelf on jemalloc_jemalloc.o, then run nm or > > readelf on malloc.o > > (2) Look at the symbols in both > > (3) Add the missing symbols to malloc.c in Bash > > The bash malloc includes definitions for malloc/free/realloc/calloc/cfree/ > valloc/memalign. I'd be interested in knowing what other global symbols > jemalloc exports. I'd also be interested in seeing how someone managed to > compile the bash malloc and leave out realloc. > > Chet Just to kind of close the loop here, we went ahead and changed our local build of bash to do: ./configure --enable-static-link --without-bash-malloc This matches the ports implementation, so we have moved on here. Sean
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