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Possible advantage

Possible advantage

Posted Jun 13, 2008 16:17 UTC (Fri) by giraffedata (subscriber, #1954)
In reply to: Possible advantage by tialaramex
Parent article: Implications of pure and constant functions

I don't really see any advantage of making the code resemble the output of the compiler.

Hear, hear. There are two distinct ways to look at a program: 1) instructions to a computer; 2) description of the solution of a computational problem. The primary audience for (1) is a computer; for (2) it's a human. In view (2), a compiler's job is to produce a machine program that computes the solution described by the source code. A lot of programmers like to do that work themselves, but I think that is an inefficient use of brain power (for everyone who works on that code).

The closer the resemblance between source and executable, the more chance you have of understanding what you're seeing in the debugger.

That's definitely my experience. But there is a middle ground. I write human-oriented code and let the compiler do its job normally. But when I debug at the machine level I add -O0 to the compile options. That's usually described as "don't optimize", but as I consider optimization to be an integral part of the compiler's job, I view it as, "Make the machine program track the source code as closely as possible."


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Possible advantage

Posted Jun 17, 2008 21:38 UTC (Tue) by roelofs (guest, #2599) [Link]

But when I debug at the machine level I add -O0 to the compile options. That's usually described as "don't optimize", but as I consider optimization to be an integral part of the compiler's job, I view it as, "Make the machine program track the source code as closely as possible."

"...and watch your bug go away." :-)

That seems to happen to me more often than not. Most recently it turned out to be a gcc code-generation bug, 32-bit only, 3.4.x only. (Pretty sure not related to const, though C++ is a different beast, so I'm not 100% certain.)

Greg

Possible advantage

Posted Jun 18, 2008 2:00 UTC (Wed) by giraffedata (subscriber, #1954) [Link]

Of all the bugs I've analyzed with GDB, I'd say about 5% stop manifesting when I disable optimization. One was a compiler optimizer bug, one was me lying to the compiler (unintentionally, of course), and the rest were wild pointers causing stack corruption.

Of course, this is mostly with older compilers. (The new ones are too slow for me).


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