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Re: [Scm-discuss] 5f2 regression: r4rstest.scm fails on 32-bit

From: Steve VanDevender
Subject: Re: [Scm-discuss] 5f2 regression: r4rstest.scm fails on 32-bit
Date: Mon, 9 Oct 2017 18:38:53 -0700

Aubrey Jaffer writes:
 > Steve VanDevender <address@hidden> writes:
 >  | Aubrey Jaffer writes:
 >  |  > I compiled scm5 with gcc-5.4.0 -m32 to make a 32-bit executable.  Your
 >  |  > examples ran in it without error.  Could it be a GCC optimizer bug?
 >  |  > Please try compiling with -O0.
 > >
 >  | I just tried compiling SCM 5f2 with -O0 on a 32-bit x86 system but still
 >  | get the test failure:
 > Without knowing what compiler version you are using, there is nothing
 > more I can do here.
 > There are 34 calls to bigrecy() in scl.c and subr.c.  You could comment
 > out half of those calls and see if it fixes the problem; then comment
 > out only 1/4 of the calls, and so forth until you isolate the call or
 > calls responsible for the error.

I agree it seems to be a case where bigrecy() is being called on a
bignum that still has a reference somewhere else.  Although with the
specific examples of numbers (in fact, neighboring integers) that
trigger and do not trigger the bug, it seems there could be a more
direct way of finding the bad bigrecy() by finding which code paths
those follow.

I built SCM with the GCC in Debian Stretch:

$ gcc -v
Using built-in specs.
Target: i686-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18' 
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr 
--program-suffix=-6 --program-prefix=i686-linux-gnu- --enable-shared 
--enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext 
--enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ 
--enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes 
--with-default-libstdcxx-abi=new --enable-gnu-unique-object 
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie 
--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk 
--enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-i386/jre 
--enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-i386 
--with-arch-directory=i386 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar 
--with-target-system-zlib --enable-objc-gc=auto --enable-targets=all 
--enable-multiarch --with-arch-32=i686 --with-multilib-list=m32,m64,mx32 
--enable-multilib --with-tune=generic --enable-checking=release 
--build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu
Thread model: posix
gcc version 6.3.0 20170516 (Debian 6.3.0-18) 

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