crash on __gmpz_init

[Marc Glisse]

Hello,

   mpz_class M[LINES][COLS];

you are trying to put an array with millions of elements on the stack, so 
the stack overflows. Very large arrays need to be allocated on the heap in 
C++ (new, malloc, or some wrapper like std::vector).

On Mon, 22 Jan 2024, igor pesando - Dept of Physics, University of Torino wrote:

> Hi *,
> first of all thanks for your work.
>
> The programs are attached as required.
>
>
> Best regards
> Igor Pesando
>
> *********************************************************************
>
> The issue I have is that the allocation in of a matrix in c++ crashes
> the program with SEGFAULT if the dimension are big enough.
>
> LINES and COLS are the number of lines and columns of a matrix.
>
>
> g++ -DLINES=5000 -DCOLS=5000 test2_mem.cpp -lgmp -lgmpxx -o t_500x500
> ./t_500x500
> version6.2.1; bits/limb 64
>
>
> g++ -DLINES=5000 -DCOLS=5000 test2_mem.cpp -lgmp -lgmpxx -o t_5000x5000
> ./t_5000x5000
> Segmentation fault (core dumped)
>
>
> The issue is not that my computer has not enough memory.
> In facts when I run the corresponding program in C it crashes in __gmpz_init
> BUT it does not crash when I allocate twice as much memory (SC is the scaling 
> factor for the allocated memory).
>
>
> gcc -DLINES=500 -DCOLS=500 -DSC=1 test2_mem.c -lgmp  -o tc_500x500
> ./tc_500x500
> allocating 250000; size=16
>
>
> gcc -DLINES=5000 -DCOLS=5000 -DSC=1 test2_mem.c -lgmp  -o tc_5000x5000
> igor at igor7a:~/tex/LCSFT/cpp/BUG_GMP_20240122$ ./tc_5000x5000
> allocating 25000000; size=16
>
>
> gcc -DLINES=7000 -DCOLS=5000 -DSC=1 test2_mem.c -lgmp  -o tc_7000x5000
> ./tc_7000x5000 -g
> allocating 35000000; size=16
> Segmentation fault (core dumped)
>
>
> Twice as much memory
> gcc -DLINES=7000 -DCOLS=5000 -DSC=2 test2_mem.c -lgmp  -o tc_7000x5000x2
> ./tc_7000x5000x2
> allocating 35000000; size=16
>
>
> **********************************************************************
> GDB
>
> gdb ./tc_7000x5000
>
> (gdb) r
> Starting program: /home/igor/tex/LCSFT/cpp/BUG_GMP_20240122/tc_7000x5000
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
> allocating 35000000; size=16
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00007ffff7f39c9b in __gmpz_init () from /lib/x86_64-linux-gnu/libgmp.so.10
> (gdb) bt
> #0  0x00007ffff7f39c9b in __gmpz_init () from 
> /lib/x86_64-linux-gnu/libgmp.so.10
> #1  0x00005555555552e9 in main () at test2_mem.c:28
>
> #1  0x00005555555552e9 in main () at test2_mem.c:28
> (gdb) f 1
> #1  0x00005555555552e9 in main () at test2_mem.c:28
> 28	      mpz_init( M[ lin*LINES +col] );
> (gdb) p lin
> $1 = 5000
> (gdb) p col
> $2 = 63
> (gdb)
>
> here lin is
> ************************************************************
>
> Please include the following in any report:
>
> ************************************************************
> The GMP version number, and if pre-packaged or patched then say so.
> gmp pre-packaged 6.2.1
> gmp 6.3.0 from sources
>
>
>
>
> ************************************************************
>
> A test program that makes it possible for us to reproduce the
> bug. Include instructions on how to run the program.
>
> In attachment
>
> ************************************************************
>    A description of what is wrong. If the results are incorrect, in
>    what way. If you get a crash, say so.
>
>    If you get a crash, include a stack backtrace from the debugger if
>    it’s informative (‘where’ in gdb, or ‘$C’ in adb).
>
> Above
>
> ************************************************************
>    Please do not send core dumps, executables or straces.
>
> ************************************************************
> The ‘configure’ options you used when building GMP, if any.
>
>    The output from ‘configure’, as printed to stdout, with any
>    options used.
>
> ************************************************************
>
>    The name of the compiler and its version. For gcc, get the version with 
> ‘gcc -v’, otherwise perhaps ‘what `which cc`’, or similar.
>
> gcc -v
> Using built-in specs.
> COLLECT_GCC=gcc
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
> OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
> OFFLOAD_TARGET_DEFAULT=1
> Target: x86_64-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Ubuntu 
> 11.4.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs 
> --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr 
> --with-gcc-major-version-only --program-suffix=-11 
> --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id 
> --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix 
> --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu 
> --enable-libstdcxx-debug --enable-libstdcxx-time=yes 
> --with-default-libstdcxx-abi=new --enable-gnu-unique-object 
> --disable-vtable-verify --enable-plugin --enable-default-pie 
> --with-system-zlib --enable-libphobos-checking=release 
> --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch 
> --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 
> --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic 
> --enable-offload-targets=nvptx-none=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-gcn/usr 
> --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu 
> --host=x86_64-linux-gnu --target=x86_64-linux-gnu 
> --with-build-config=bootstrap-lto-lean --enable-link-serialization=2
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)
>
>
> ************************************************************
>
> The output from running ‘uname -a’.
>
> Linux igor7a 6.5.0-14-generic #14~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC
> Mon Nov 20 18:15:30 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
>
> ************************************************************
>
> The output from running ‘./config.guess’, and from running 
> ‘./configfsf.guess’ (might be the same).
>
>
> ./config.guess
> kabylake-pc-linux-gnu
>
> sh ./configfsf.guess
> x86_64-pc-linux-gnu

-- 
Marc Glisse