CMake: ‘sqrtf’ is not a member of ‘std’

Question

After compiling my program with

$ cmake .
$ make

I get 5 errors of this form:

$ make
Scanning dependencies of target Project
[ 50%] Building CXX object CMakeFiles/myproj.dir/main.cpp.o
In file included from /path/to/my/proj/main.cpp:2:0: 
/path/to/my/proj/library.hpp: In member function ‘virtual double MyProjClass::get_value(double, double) const’:
/path/to/my/proj/library.hpp:419:26: error: ‘sqrtf’ is not a member of ‘std’
     const float F = (std::sqrtf(1.0f + 2.0f) - 1.0f) / 2;
                      ^

Other errors include floorf not being a member of std.

Looking at this thread, it's because I'm not compiling with C++11, and looking at this thread thread, "[...] CMake will make sure the C++ compiler is invoked with the appropriate command line flags."

Well, my CMake is obviously not doing this. Why am I getting these errors, and how do I go about fixing them?

Edit: Here's my CMakeLists.txt

cmake_minimum_required(VERSION 3.5)
project(Noise)

set(CMAKE_CXX_STANDARD 11)

set(SOURCE_FILES main.cpp vector.hpp noise.hpp)
add_executable(Noise ${SOURCE_FILES})

find_package(SDL2 REQUIRED)
include_directories(${SDL2_INCLUDE_DIRS})
target_link_libraries(Noise ${SDL2_LIBRARIES})

The problem is either in your `CMakeLists.txt` file, or in your C++ code. You haven't shown either, so we cannot help. — Angew is no longer proud of SO, Apr 03 '17 at 11:41
Why use `sqrtf` or `floorf`? Especially with c++11, `sqrt` is able to handle `float`s directly. — oLen, Apr 03 '17 at 11:50
@Angew Added CMakeLists.txt oLen: Your comment solved this. Replacing all instances of floorf and sqrtf with floor and sqrt removed the errors. No idea why. — Mossmyr, Apr 03 '17 at 12:11

score 7 · Accepted Answer · answered Apr 03 '17 at 11:52

7

You don't say what C++ compiler you are using but assuming it is g++ 5.x though 7, sqrtf and floorf are not within the std namespace under -std=c++11, -std=c++14 or -std=c++1z. They are simply in the global namespace, when cmath is included.

answered Apr 03 '17 at 11:52

Mike Kinghan

55,740
12
153
182

7

That makes the standard library in question non-conforming. All C standard library names are supposed to be placed in `::std` when the `` headers are used. – Angew is no longer proud of SO Apr 03 '17 at 12:16
Agree. `` must put them in `std::` and may also put them in the global namespace; `` is the other way around. – MSalters Apr 03 '17 at 13:21

CMake: ‘sqrtf’ is not a member of ‘std’

1 Answers1