Linker warning "_getentropy is not implemented and will always fail"

[bastetfurry]

Trying to compile my project i get the following warning after an OS upgrade that also brought in a new version of GCC:

/usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-getentropyr.o): in function `_getentropy_r':
/build/newlib-38V0JC/newlib-4.4.0.20231231/build/arm-none-eabi/thumb/v6-m/nofp/newlib/../../../../../../newlib/libc/reent/getentropyr.c:48:(.text+0xe): warning: _getentropy is not implemented and will always fail
/usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc.a(libc_a-getentropyr.o): note: the message above does not take linker garbage collection into account

OS: Ubuntu 24.04
GCC: arm-none-eabi-gcc (15:13.2.rel1-2) 13.2.1 20231009
SDK: v1.6.1

Can this safely be ignored for now or can i do something against this, besides downgrading the compiler?

[kilograham]

i have not seen this; can you provide a minimal repro; is this with C++? are you calling something that might need getentropy?

[jaguilar]

I saw this when I upgraded to the latest LTS of Ubuntu. It might be something that gets noticed with a new version of GCC and/or a new version of newlib?

[lurch]

This at least shows that this problem isn't specific to just pico-sdk 😉

[kilograham]

Yeah, i'm sure it is a problem with newlib however the reason I asked for a repro case, is that i couldn't reproduce it!! (and then work around it)

[bastetfurry]

Sorry, haven't gotten around to create one yet. I don't want to FOSS my project just yet as i want it in a releaseworthy state, but if you could keep it under the lid until i am prepared to release it i could send you a copy.
I am using Elmchans FatFS as a library but everything else is just the normal Pico SDK and the normal C and C++ library.

[bastetfurry]

As a sidenote, everything works as expected, so for now it seems one can ignore that warning.

[kilograham]

ok, yeah maybe just worth looking at the .DIS file and see if there are any references to entropy

[bastetfurry]

CLion says "Nope"

[bastetfurry]

Oh, cool, this is my whole project in assembler, thanks for showing me that! ❤️

[dementedmonkey]

Not sure if you still need that minimal repro case, but here's mine:
CMakeLists.txt

cmake_minimum_required(VERSION 3.5)
include($ENV{PICO_SDK_PATH}/external/pico_sdk_import.cmake)
set(PICOTOOL_FETCH_FROM_GIT_PATH $ENV{PICO_SDK_PATH}/fetch)
set(target_proj bug)
project(${target_proj} C CXX)
pico_sdk_init()
add_executable(${target_proj} main.cpp )
target_link_libraries(${target_proj}  pico_stdlib )

main.cpp:

#include <queue>

int main()
{
    std::queue<int> queue;
}

build commands:

#! /bin/bash
rm -rf build
/usr/bin/cmake -DCMAKE_BUILD_TYPE:STRING=Debug -S. -B./build
/usr/bin/cmake --build ./build --config Debug --target all

It seems the -DCMAKE_BUILD_TYPE is part of the trigger. If that's not present, I don't see the warnings