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c++gccg++pragma

GCC #pragma or command options

If the compiler has some command-line flags and the code has some pragmas that are incompatible with those flags, which one will be used?

To be clearer: I am compiling with g++ -g -O2 -std=gnu++17 -static {files} – GCC version g++ (Ubuntu 9.3.0-10ubuntu2) 9.3.0.

If I write in my code #pragma GCC optimize("Ofast"), will the final code be compiled with -O2 or with -Ofast?

Solution

  • That depends on if it's above or below the pragma.

    void this_will_be_compiled_with_O2() { stuff(); }

#pragma GCC optimize("Ofast")

void this_will_be_compiled_with_Ofast() { stuff(); }