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Re: compilation failure

From: Jim Meyering
Subject: Re: compilation failure
Date: Wed, 30 Mar 2011 15:41:33 +0200

Eli Zaretskii wrote:
>> From: Jim Meyering <address@hidden>
>> Date: Wed, 30 Mar 2011 09:42:42 +0200
>> Cc: address@hidden, address@hidden
>> This command,
>>   env MALLOC_PERTURB_=0 MALLOC_CHECK_=0 make -j9 bootstrap
>> has succeeded for me on each of the last three mornings (Mar 28-30).
>> I manually set those two MALLOC_*_ variables to 0 because
>> when I don't, emacs fails to bootstrap.
> It's a pity this problem was not reported to the bug tracker.  (At
> least I couldn't find it; apologies if I missed it.)

I thought I reported it to some emacs development list months ago,
but a quick search didn't find it.

>> I suspect that emacs is using free'd memory containing
>> values that would normally be unoffensive, but when you set
>> those envvars (esp MALLOC_PERTURB_) to nonzero, it makes
>> glibc scribble on free'd buffers, and that makes emacs
>> exhibit an actual failure.
> Can you use bisect to find the guilty commit?

Finding a commit for which a perturbed "make bootstrap" succeeds
was a challenge.

I bootstrapped 8 or 10 times, going back to 2009
in steps of 500, then 1500 commits.  Same failure
each time, until I started getting link errors:

  /usr/bin/ld: xftfont.o: undefined reference to symbol 'XRenderQueryExtension'
  /usr/bin/ld: note: 'XRenderQueryExtension' is defined in DSO 
/usr/lib64/libXrender.so.1 so try adding it to the linker command line
  /usr/lib64/libXrender.so.1: could not read symbols: Invalid operation

I worked around that by inserting -lXrender into the generated Makefile:

    perl -pi -e 's/(-lfreetype )/$1-lXrender /' src/Makefile

With that, I finally found a successful build at this git commit:

commit 84655cfe88efb24c256302d016cd037d22544cca
Author: Stefan Monnier <address@hidden>
Date:   Fri Nov 6 18:47:48 2009 +0000

    Let integers use up 2 tags to give them one extra bit and double their 
    * lisp.h (USE_2_TAGS_FOR_INTS): New macro.
    (LISP_INT_TAG, case_Lisp_Int, LISP_STRING_TAG, LISP_INT_TAG_P): New macros.

Maybe someone else will do the actual bisection:

    Bisecting: 4164 revisions left to test after this (roughly 12 steps)

This is the command to run:

    env MALLOC_PERTURB_=44 MALLOC_CHECK_=3 make -j9 bootstrap

If not, I'll get to it, eventually.

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