CODEWITHSUNDEEP
gcc
tothphu
tothphu

Reputation: 979

how will gcc react to -O2 and -O0 in the same command?

Anyone has any ideas which will take preference if -O2 and -O0 is specified in the command line for gcc? I have some legacy code that gets configuration from multiple places....

Upvotes: 2

Views: 434

Answers (2)

wkl
wkl

Reputation: 80031

λ > g++ outer.cxx -O2 -Os -o outer
λ > sha1sum outer                 
c3f62ab60393266388a8a7fb2d204d4b1f9dc145  outer
λ > g++ outer.cxx -Os -O2 -o outer
λ > sha1sum outer
355052e82d0146a185c8a1b845c7ed6db18087f1  outer
λ > g++ outer.cxx -O2 -o outer
λ > sha1sum outer
355052e82d0146a185c8a1b845c7ed6db18087f1  outer
λ > g++ outer.cxx -Os -o outer
λ > sha1sum outer
c3f62ab60393266388a8a7fb2d204d4b1f9dc145  outer

The last specified optimization flag wins.

Upvotes: 3

Charlie Martin
Charlie Martin

Reputation: 112414

Last flag wins. That lets them be overridden in a makefile.

Upvotes: 4

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