Reliable Source: Lessons from a Life in Software Engineering by Bonang Clarisse & Bonang James

Author:Bonang, Clarisse & Bonang, James
Language: eng
Format: epub
Published: 2022-01-12T00:00:00+00:00

This suggests that thread T1, fnThreadA, is also accessing that same location, offset 64 bytes (40 in hexadecimal) from the start of the Cryptanalyzer object (0x7b1800000000).

The next block of messages from TSan confirms our suspicions. The race condition involves memory allocated on the heap beginning at hexadecimal address 0x7b1800000000 and allocated by the newInstance simple factory method of the Cryptanalyzer class using the new operator.

Location is heap block of size 96 at 0x7b1800000000 allocated by main thread:

#0 operator new(unsigned long) <null> (libtsan.so.0+0x7502a)

#1 Cryptanalyzer::newInstance(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) /home/jbonang/projects/study_in_concurrency/Cryptanalyzer.cpp:52 (cryptanalyzer+0x402df0)

#2 main /home/jbonang/projects/study_in_concurrency/main.cpp:103 (cryptanalyzer+0x40ef80)

Figure 50: ThreadSanitizer reports location of data race

We have an airtight case: the member variable vecCandidatePlaintextFitnessMeasureTuple within the Cryptanalyzer object passed to threads A (T1) and T (T2), is a vector of tuples and is not thread safe, leading to race conditions.

std::vector< std::tuple<std::string, double> > m_vecCandidatePlaintextFitnessMeasureTuple;

Figure 51: C++ code fragment showing our prime suspect, the vector of tuples

Our suspect has the means, opportunity and, of course, motive. It has accomplices in the form of our two threads. Our suspect will hang for this - well, actually, not hang, but "seg fault."

Even the worst of criminals may not be beyond redemption, though. What can be done to rehabilitate our perpetrator?

Rehabilitation

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