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@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
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