[PATCH] Allow to use different prefixes for jemalloc-specific functions and libc functions

Mike Hommey mh+jemalloc at glandium.org
Mon Mar 12 12:28:06 PDT 2012

On Mon, Mar 12, 2012 at 11:44:41AM -0700, Jason Evans wrote:
> On Mar 12, 2012, at 2:49 AM, Mike Hommey wrote:
> > On Thu, Mar 01, 2012 at 05:49:33PM -0800, Jason Evans wrote:
> >> On Mar 1, 2012, at 6:44 AM, Mike Hommey wrote:
> >>> On Wed, Feb 29, 2012 at 04:15:37PM -0800, Jason Evans wrote:
> >>>> On Feb 23, 2012, at 3:23 AM, Mike Hommey wrote:
> >>>>> From: Mike Hommey <mh at glandium.org>
> >>>>> 
> >>>>> In some cases, it can be interesting to use different prefixes for
> >>>>> the "standard" libc malloc functions and for jemalloc specific
> >>>>> functions. One such case is to use the "__wrap_" prefix on libc
> >>>>> malloc functions (for use with ld's --wrap option) and no prefix or
> >>>>> "je_" for jemalloc functions.
> >>>>> 
> >>>>> In such cases, it can also me interesting not to exclude memalign
> >>>>> and valloc, so this change also adds an option not to omit them when
> >>>>> the prefix is set.
> >>>> 
> >>>> Do you have a practical use case that makes this a compelling feature?
> >>>> I'm reluctant to hard-code the set of JEMALLOC_LIBC() functions to
> >>>> make distinct from JEMALLOC_P() functions, because it may vary by
> >>>> operating system.
> >>> 
> >>> The exact one that is in the patch message: on android, we use ld's
> >>> --wrap option to wrap the "standard" libc functions. It is cumbersome
> >>> to have to use --wrap for jemalloc-specific functions as well.
> >>> Arguably, we could probably use symbol aliases when linking the library
> >>> containing jemalloc.
> >> 
> >> I went a slightly different direction with this and added --with-mangling:
> >> 
> >>  http://www.canonware.com/cgi-bin/gitweb.cgi?p=jemalloc.git;a=commitdiff;h=0a5489e37da88a1a50fbf8552e0d3a7f8fd93ffc
> >> 
> >> Please let me know if this fails to meet your needs for some reason.
> > 
> > The fact that --with-jemalloc-prefix overrides anything set with
> > --with-mangling makes it unconvenient for our usecase, where we want to
> > prefix with je_ except a few functions we want to either not prefix (on
> > desktop) or wrap (on android). Sure, we can use --with-mangling to set
> > the je_ prefix, but that won't cover new APIs when they appear.
> The name mangling that is specified via --with-mangling overrides --with-jemalloc-prefix, so I thought this would do what you want.
> ./autogen.sh --enable-cc-silence --enable-prof --enable-debug --with-mangling=malloc:__wrap_malloc,calloc:__wrap_calloc,realloc:__wrap_realloc,free:__wrap_free --with-jemalloc-prefix=je_

After running that, this is what jemalloc_defs.h contains:
#define je_malloc_conf je_malloc_conf
#define je_malloc_message je_malloc_message
#define je_malloc je_malloc
#define je_calloc je_calloc
#define je_posix_memalign je_posix_memalign
#define je_realloc je_realloc
#define je_free je_free
#define je_malloc_usable_size je_malloc_usable_size
#define je_malloc_stats_print je_malloc_stats_print
#define je_mallctl je_mallctl
#define je_mallctlnametomib je_mallctlnametomib
#define je_mallctlbymib je_mallctlbymib
#define je_memalign je_memalign
#define je_valloc je_valloc
#define je_allocm je_allocm
#define je_rallocm je_rallocm
#define je_sallocm je_sallocm
#define je_dallocm je_dallocm
#define je_nallocm je_nallocm

Even without --with-jemalloc-prefix=je_, I get the same output.


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