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July 31st, 2011, 11:48 PM
#1
What's wrong with this simple Boost multithreaded function?
The code snippet below is the core of a function mythreadfunc() that is run concurrently for several threads using CreateThread() and WaitForMultipleObjects(). Everything seems to work fine except actually using boost::regex_match(). For example, if that line is changed to if(true), the entire multithreaded function works perfectly. Similarly, if mythreadfunc() as shown below is run "normally" without multiple threads, it works perfectly. But if mythreadfunc() as shown below is run with multiple threads, the entire program crashes with return value 0xc0000005 "access violation."
This leads me to believe that boost::regex is not thread safe, but according to the boost site, there aren't any bugs related to this issue for boost 1.45. As far as I can tell I'm using boost in thread safe mode (BOOST_HAS_THREADS is defined). I'm probably doing something really dumb related to MSVC threads or related to the way I configured boost, but I'm not sure what it is! Thanks for any ideas or help~
Code:
static const boost::regex expression("^[0-9]+");
ifstream myfile(x);
string line;
if(myfile.is_open())
{
while(myfile.good())
{
getline(myfile, line);
if(boost::regex_match(line, expression))
{
//do stuff
}
}
myfile.close();
Last edited by andrew732; July 31st, 2011 at 11:51 PM.
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August 1st, 2011, 10:15 AM
#2
Re: What's wrong with this simple Boost multithreaded function?
Well, I'm not sure 'ifstream' is thread safe.
Viggy
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August 2nd, 2011, 05:15 PM
#3
Re: What's wrong with this simple Boost multithreaded function?
Originally Posted by andrew732
The code snippet below is the core of a function mythreadfunc() that is run concurrently for several threads
In general, it's better not to read/write to disk from several threads. Hard disk access is a bottleneck on normal pc's and reading several files at the same time can be much slower than reading them sequentially.
Cheers, D Drmmr
Please put [code][/code] tags around your code to preserve indentation and make it more readable.
As long as man ascribes to himself what is merely a posibility, he will not work for the attainment of it. - P. D. Ouspensky
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