Why doesn't gcc10 see the -fcoroutines flag?

Question

I am trying to compile a program with #include <coroutine> header file included in it. But gcc10 throws an error

/usr/include/c++/10/coroutine:295:2: error: #error "the coroutine header requires -fcoroutines"
  295 | #error "the coroutine header requires -fcoroutines"

I set all the necessary flags in cmake

cmake_minimum_required(VERSION 3.17)
project(cortest1)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_FLAGS "-fcoroutines")
set(CMAKE_CXX_FLAGS "-pthread")

add_executable(cortest1 main.cpp)

But the compiler doesn't see the -fcoroutines flag. I am using g ++ 10.2.0

use `make VERBOSE=1` to see the actual command; this looks like a cmake configuration error — Jaffa, Jan 02 '21 at 15:10

eerorika · Accepted Answer · 2021-01-02T19:29:25.877

2

set(CMAKE_CXX_FLAGS "-pthread")

After you set the flags to -pthread, it no longer has the previous value that had the coroutine flag.

P.S. Use target specific configuration i.e. don't set CMAKE_CXX_FLAGS. Use target_compile_options instead. And use target_compile_features instead of setting CMAKE_CXX_STANDARD.

edited Jan 02 '21 at 19:29

answered Jan 02 '21 at 16:00

eerorika

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Why doesn't gcc10 see the -fcoroutines flag?

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