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Examining the User-Reported Issues With Upgrading From GCC 4.7 To 4.8
Nerval's Lobster writes "Developer and editor Jeff Cogswell writes: 'When I set out to review how different compilers generate possibly different assembly code (specifically for vectorized and multicore code), I noticed a possible anomaly when comparing two recent versions of the g++ compiler, 4.7 and 4.8. When I mentioned my concerns, at least one user commented that he also had a codebase that ran fine after compiling with 4.6 and 4.7, but not with 4.8.' So he decided to explore the difference and see if there was a problem between 4.7 and 4.8.1, and found a number of issues, most related to optimization. Does this mean 4.8 is flawed, or that you shouldn't use it? 'Not at all,' he concluded. 'You can certainly use 4.8,' provided you keep in mind the occasional bug in the system."
Thanks for another worthless uninformative article.
The article basically says:
"GCC 4.8 includes new optimizations! Because of this, the generated assembly code is different! This might be BAD."
Like, duh? Do you expect optimizations to somehow produce the same assembly as before, except magically faster?
The linked "bug" is here: http://stackoverflow.com/questions/19350097/pre-calculating-in-gcc-4-8-c11 - which says, "Hey, this certain optimization isn't on by default anymore?" And to which the answer is, "Yeah, due to changes in C++11, you're supposed to explicitly flag that you want that optimization in your code."
So, yeah. Total non-story.
He actually observed that different assembler code was generated - well how do you think can you generate _faster_ assembler code without generating _different_ assembler code?
The article does _not_ make any claim that any code would be working incorrectly, or give different results. The article _doesn't_ examine any user-reported issues. So on two accounts, the article summary is totally wrong.