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Re: GNU OSC (Object Size Checking)
On 02/06/2018 10:52 PM, Yuchen Zhou (yuczhou) wrote:
Thank you Martin, Jonathan. I think I understand it now. Of cause I may have further questions in the future.
By the way, is the -O2 option a must for OSC? What about other optimization levels? I did not find much details on it.
No, it works at -O1, although it may not detect as many instances
of overflow as it does with more optimization, or even with LTO.
The best way to find out when it's effective it is to experiment
with some test cases and compare the output (warnings, assembly,
and/or GCC dumps) between -O1 and higher levels. There may be
warnings and no runtime instrumentation or (rarely) instrumentation
but no warnings. If/when you find differences between -O levels
you can then look at the internal compiler dumps to figure out
which optimization pass is responsible. Compile with
-fdump-tree-all and look at the files (there will be many).
The name of the pass that implements OSC is "objsz" so look for
output named <source-file>.<number>t.objsz<number>.
Martin