https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99418
Bug ID: 99418
Summary: sanitizer checks for accessing multidimentional
VLA-array
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: vanyacpp at gmail dot com
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
The example below accesses array past its size, but sanitizers don't show any
errors. If I change index m to m + 1 an error will be shown. This makes me
think that compiler does some checks, but perhaps they are incomplete for
multidimentional VLA-arrays.
GCC 10.2.
#include <string>
std::string shortest_match(size_t n, size_t m)
{
std::string mas[n][m];
mas[n - 1][m] = ""; // mas[n - 1][m + 1] will show an errors
return mas[n - 1][m - 1];
}
int main()
{
shortest_match(4, 3);
}
$ g++ -g -fsanitize=address,undefined -std=c++17 2.cpp && ./a.out
AddressSanitizer:DEADLYSIGNAL
=================================================================
==26974==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc
0x7f59ea2ad2d6 bp 0x000000000000 sp 0x7ffc78389ea0 T0)
==26974==The signal is caused by a WRITE memory access.
==26974==Hint: address points to the zero page.
#0 0x7f59ea2ad2d6 in std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >::_M_replace(unsigned long,
unsigned long, char const*, unsigned long) (/lib/libstdc++.so.6+0x13c2d6)
#1 0x401658 in shortest_match[abi:cxx11](unsigned long, unsigned long)
/home/ivan/2.cpp:6
#2 0x4019eb in main /home/ivan/2.cpp:13
#3 0x7f59e950ec7c in __libc_start_main (/lib/libc.so.6+0x23c7c)
#4 0x4011a9 in _start (/home/ivan/a.out+0x4011a9)
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/lib/libstdc++.so.6+0x13c2d6) in
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>
>::_M_replace(unsigned long, unsigned long, char const*, unsigned long)
==26974==ABORTING
