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devel / comp.lang.c++ / Iterator-debugging even works across thread-boundaries

Iterator-debugging even works across thread-boundaries

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https://www.rocksolidbbs.com/devel/article-flat.php?id=1086&group=comp.lang.c%2B%2B#1086

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From: Bonita.Montero@gmail.com (Bonita Montero)
Newsgroups: comp.lang.c++
Subject: Iterator-debugging even works across thread-boundaries
Date: Sat, 19 Aug 2023 13:39:50 +0200
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by: Bonita Montero - Sat, 19 Aug 2023 11:39 UTC

I just tested if iterator debugging is thrread-safe.

#include <thread>
#include <string>
#include <semaphore>

using namespace std;

int main()
{ constexpr size_t N = 1ull << 20;
binary_semaphore semZero( false );
jthread thread;
{
binary_semaphore semHalf( 0 );
string str( N, '*' );
thread = jthread( [&]( string &str )
{
char sum = 0;
for( string::iterator it = str.begin(), brk = it + N / 2, end =
str.end(); it != end; *it++ = '+' )
if( it == brk )
semHalf.release( 1 ),
semZero.acquire();
}, ref( str ) );
semHalf.acquire();
}
semZero.release( 1 );
}

So with iterator debugging you can have use after free protection at
least with MSVC. I tried that with g++'s libstdc++ (-D_GLIBCXX_DEBUG)
and libc++ (-D_LIBCPP_DEBUG=1) and I get a normal crash instead of
debugging information.

Subject	Author
Iterator-debugging even works across thread-boundaries	Bonita Montero