c++ -O2 -o aec aec.cpp

[c_lady]

Please let me know what -O2 means? I can compile this file "http://read.pudn.com/downloads169/sourcecode/unix_linux/777160/aec/aec-test.c__.htm"
but I dont really know what the heck means this -O2

Thanks!

[RichSelian]

-O1 Optimize. Optimizing compilation takes somewhat more time, and a lot more memory for a large function.
-O2 Optimize even more. GCC performs nearly all supported optimizations that do not involve a space-speed tradeoff. As compared to -O, this option increases both compilation time and the performance of the generated code.
-O3 Optimize yet more. -O3 turns on all optimizations specified by -O2 and also turns on the -finline-functions, -funswitch-loops, -fpredictive-commoning, -fgcse-after-reload and -ftree-vectorize options.
-O0 Reduce compilation time and make debugging produce the expected results. This is the default.
-Os Optimize for size. -Os enables all -O2 optimizations that do not typically increase code size. It also performs further optimizations designed to reduce code size.

Copied from gcc's manual