Number:IRCNE2014062224
Date: 2014-06-20
According to “computerworld”, as if tracking down bugs in a complex application isn't difficult enough, programmers now must worry about a newly emerging and potentially dangerous trap, one in which a program compiler simply eliminates chunks of code it doesn't understand, often without alerting the programmer of the missing functionality.
The code that can lead to this behavior is called optimization-unstable code, or "unstable code," though it is more of a problem with how compilers optimize code, rather than the code itself, said Xi Wang, a researcher at the Massachusetts Institute of Technology.
With unstable code, programs can lose functionality or even critical safety checks without the programmer's knowledge.
The researchers have developed a new technique for finding unstable code in C and C++ programs, called Stack, that they hope compiler makers will use when updating their products.
Using Stack, the research team has found over 160 bugs in various programs due to unstable code.
The research looked at 16 open source and commercial C/C++ compilers -- from companies such as Intel, IBM and Microsoft -- and had found they all dropped unstable code.
A compiler can issue warnings when it drops code, though compilers typically issue so many warnings, especially for large programs, that a notice of code being eliminated may be lost in the deluge of other largely inconsequential messages.
"I think compiler developers have known about this for years," Wang said.
Not all the blame should be placed on the compiler makers, noted Peng Wu, a researcher at Huawei America Labs who was at the presentation.
Wu noted that optimization was a chief priority for compiler makers in previous decades, when developers tried to get the best performance from the hardware as possible. Over the past decade however, has more attention been placed on finding bugs, due to the growing impact of security vulnerabilities, and so the problem of unstable code is now surfacing.
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